CN120615170A

CN120615170A - Device and method for connecting to a multi-core cable

Info

Publication number: CN120615170A
Application number: CN202480009341.7A
Authority: CN
Inventors: A·达姆斯; V·皮亚扎; M·布鲁姆; J·霍克斯福德; M·坎托; 詹姆斯·埃维特; J·黑格
Original assignee: Sensus Spectrum LLC
Current assignee: Sensus Spectrum LLC
Priority date: 2023-01-31
Filing date: 2024-01-30
Publication date: 2025-09-09
Also published as: WO2024161128A1

Abstract

Apparatus and methods for coupling to a multi-core wire armored cable or multi-core cable are described. The device may include one or more magnets and one or more magnetic field sensors, and/or may include an array of two or more one or more sensors to enable accommodation of twisting of multiple conductors or cores. The apparatus is configured such that when the apparatus is coupled to the multi-core wire-armored cable, a magnetic field corresponding to the one or more magnets is applied to an area of the multi-core wire-armored cable. The apparatus is configured such that when the apparatus is coupled to the multi-core wire-armored cable, each magnetic field sensor is oriented to detect a magnetic field component originating from the region of the multi-core wire-armored cable.

Description

Apparatus and method for coupling to a multi-core cable

Technical Field

The present invention relates to an apparatus and method for contactless measurement of current in a multi-core cable. In some examples, the multi-core cable may be armored. In some examples, a multi-core cable may be used to supply the net current.

Background

The magnetically permeable housing around the current carrying cable reduces the magnetic field around the cable due to the current within the cable, making it impractical to measure any current in the cable other than the net current running at the center of the cable. The net current is measured by a conventional current transformer or Rogowski (Rogowski) coil placed around the cable. Thus, information about (among other information) differential currents and conductor positioning within the cable in the external magnetic field may be lost.

Prior art related to the invention:

WO2013/068360A1 (2013) discloses an apparatus for measuring current in conductors of armoured cables of a multiphase network. The invention comprises at least six magnetic field sensors arranged around a central bore. The cable to be measured passes through the central hole and the number of conductors in the cable must be smaller than the number of magnetic field sensors. The invention includes a computing device and a matrix library that relates measured fields to currents in conductors when the conductor configuration is known. A procedure is described for selecting and optimizing an optimal matrix and adapting it to a set of conductors under test. WO2013/068360A1 offers significant advantages over documents such as EP0874244B1 in that the total current is not limited to zero, the number of unconstrained sensors is equal to the number of conductors minus 1, and allows to adapt to unexpected conductor configurations under certain constraints.

Thus, methods are known in the art for deriving the current in a non-armored multi-core cable from a magnetic field. Examples are disclosed in patent application WO2013/068360 A1.

The invention disclosed in this specification addresses the need in the art for measuring current in a steel wire armored multi-core cable that has not been addressed.

Single conductor current sensors (e.g., current transformers and rogowski coil units) based on gaussian law and current magnetic fields have been the mainstay of electrical measurement. They rely on faraday's law, requiring that a sensor be placed around each conductor and give an accurate reading of the net current enclosed, independent of the material used in the cable (magnetic or other material).

Systems for simultaneously measuring multiple conductors in the same cable have been demonstrated. Conventionally, however, this requires separating each conductor and measuring the current in each conductor-CT, rogowski, shunts, etc. US5,473,244A, US7,755,347B1 and EP0874244A2 have discussed methods of sensing currents in multiple conductors within the same cable without the need to separate the conductors.

Disclosure of Invention

The present description relates in part to methods and apparatus for applying a magnetic field to saturate the magnetically permeable shell of an armored multi-core cable, reducing its effective permeability, and allowing the magnetic field generated by the current distribution within the cable to reach the outside. In this way, a technique of calculating an internal current distribution from the external field measurement result can be employed.

Typical armored cables use steel wires wrapped around conductors to provide a partially magnetically conductive housing and attenuate and distort the magnetic field due to the current distribution within the cable. As described herein, this effect is reduced (or effectively eliminated) by the magnetic saturation of the steel wire, allowing accurate and repeatable measurements of the field generated due to the current distribution within the cable. Based on the magnetic field, the current distribution may be calculated to produce derived parameters such as, but not limited to, time domain currents, conductor currents, differential currents, phases, harmonics, the number and/or geometry of cores within the multi-core wire-armoured cable and/or the unarmored multi-core cable, etc. in one or more individual cores.

According to a first aspect of the present invention, there is provided an apparatus for coupling to a multi-core wire-armoured cable. The device includes one or more magnets and one or more magnetic field sensors. The apparatus is configured such that when the apparatus is coupled to the multi-core wire-armored cable, a magnetic field corresponding to the one or more magnets is applied to an area of the multi-core wire-armored cable. The apparatus is configured such that when the apparatus is coupled to the multi-core wire-armored cable, each magnetic field sensor is oriented to detect a magnetic field component originating from the region of the multi-core wire-armored cable.

The magnets may be rare earth magnets (e.g., samarium cobalt (SmCo) and/or neodymium (NdFeB)) and/or other non-rare earth magnets.

Since the magnet may be fragile, it may be desirable to protect it from mechanical shock or impact. The magnets may be coated with rubber or other polymers. One or more magnets may be overmolded with a polymer, or assembled with one or more rigid polymeric or metallic (magnetic or non-magnetic material) covers that protect the surface of the magnet that would otherwise be exposed to impact.

In this way, the magnetic field from the one or more magnets may saturate, or at least partially saturate, the wire armor (typically in the form of wires wrapped around the multi-core cable). Thus, the permeability of the steel wire armour is reduced, allowing more of the magnetic field generated by the current in the core of the cable to be coupled to the magnetic field sensor. This can improve the accuracy and reliability of the measured magnetic field due to differential current between two or more cores (or conductors) of the multi-core wire-armoured cable. Thus, the derived quantity calculated based on the measured magnetic field can also be improved. Examples of derived quantities may include, but are not limited to, time domain currents, differential currents, phases, harmonics, number and/or geometry of cores within a multi-core wire-armoured cable, etc. in one or more individual cores.

Each magnetic field sensor may be oriented to detect a magnetic field component from a current flowing through one or more wire cores within a region of the multi-core wire-armoured cable to which a magnetic field corresponding to one or more magnets is applied. The magnetic field sensor may be configured to measure a magnetic field generated by a differential current between two or more cores of the multi-core wire-armoured cable.

Alternatively, the multi-conductor cable may be referred to as a multi-conductor cable (these terms should be interpreted interchangeably).

The magnetic field corresponding to the one or more magnets corresponds to a superposition of magnetic fields generated by each of the one or more magnets.

Coupling may include mechanical coupling and/or connection. The coupling may include linking magnetic flux generated by or within the multi-core wire-armoured cable and/or its core. The coupling does not include a DC electrical connection.

When the device is coupled to a multi-core wire-armored cable, the magnetic field corresponding to the one or more magnets may include a component parallel to the axial direction of the multi-core wire-armored cable within the region. This component parallel to the axial direction of the multi-core wire-armoured cable may be the largest component of the magnetic field at each point within the region. The component parallel to the axial direction of the multi-core wire-armoured cable may be the maximum total component of the magnetic field.

At least one of the one or more magnets may comprise a permanent magnet or take the form of a permanent magnet. Two or more of the magnets may comprise permanent magnets or take the form of permanent magnets. All of the one or more magnets may comprise or take the form of permanent magnets.

At least one of the one or more magnets may comprise or take the form of an electromagnet. Two or more of the magnets may comprise or take the form of electromagnets. All of the one or more magnets may comprise or take the form of electromagnets.

At least one of the one or more magnetic field sensors may comprise or take the form of a coil. Two or more of the magnetic field sensors may comprise or take the form of respective coils. All of the one or more magnetic field sensors may comprise or take the form of respective coils. The coil may be prefabricated with the cable inserted therein, or wound around the cable in situ, or connected around the cable in situ, or placed around the cable in situ. The coils may be mounted radially with respect to the longitudinal axis of the sensor, tangentially or along other axes. A mix of coil orientations may be used, such as, but not limited to, radial and tangential within a single sensor. The coil may be wound on a magnetic core of magnetically permeable material. The coil may be a so-called "air core" coil, which does not comprise a magnetic core of magnetically permeable material. The "air core" coil may be wound on a support structure formed of a non-magnetically permeable material (e.g., plastic, glass, etc.).

At least one of the one or more magnetic field sensors may comprise or take the form of a solid state magnetic field sensor device. Each solid state magnetic field sensor may sense a magnetic field in one axis, two axes, three axes, or more. The solid state magnetic field sensor device may comprise or take the form of a semiconductor-based magnetic sensor, a magneto-resistive sensor, a giant magneto-resistive sensor or an anisotropic magneto-resistive sensor. The solid state magnetic field sensor device may comprise or take the form of a giant magneto-impedance (GMI) sensor. The solid state magnetic field sensor device may comprise or take the form of a superconducting quantum interference detector (SQUID). The solid state magnetic field sensor device may comprise or take the form of a magneto-optical sensor. The solid state magnetic field sensor device may comprise or take the form of a fluxgate. The solid state magnetic field sensor device may comprise or take the form of a chip or an integrated circuit. The solid state magnetic field sensor device may comprise or take the form of a hall sensor.

Two or more of the magnetic field sensors may include or take the form of respective solid state magnetic field sensing devices (of any of the types described herein). All of the one or more magnetic field sensors may include or take the form of respective solid state magnetic field sensing devices (of any of the types described herein).

The magnetic field corresponding to the one or more magnets may have an amplitude of at least 5mT in the region. The magnitude of the magnetic field corresponding to the one or more magnets may be at least 12mT in the region. The magnitude of the magnetic field corresponding to the one or more magnets may be at least 50mT in the region.

The magnetic field corresponding to the one or more magnets may vary over time. The time-varying magnetic field may correspond to at least some of the one or more magnets in the form of electromagnets. At least some of the electromagnets may be driven by alternating current. At least some of the electromagnets may be energized during an active period (active period) and de-energized during an inactive period (inactive period). The device may be configured to compare magnetic field measurements between active and inactive periods to identify and preferably compensate for residual shielding effects of the wire armor. The active and inactive periods may be ordered according to a predetermined schedule. Additionally or alternatively, the apparatus may be configured to energize at least some of the electromagnets in response to a trigger condition, a received signal, or the like.

The apparatus may be configured such that a magnetic field corresponding to the one or more magnets is constant. Constant may mean that the magnetic field is not time-varying when properly powered and operated. The constant magnetic field may be provided by a permanent magnet, an electromagnet powered by a DC current, or a combination of both.

The apparatus may be configured to mechanically couple to the multi-core wire-armoured cable using a magnetic force generated by applying a magnetic field to the wire-armour layer. The one or more magnets may be primarily configured to apply a magnetic field to the region to at least partially saturate the steel wire armor. However, this always creates a certain magnetic force between the device and the multi-core wire-armoured cable. The magnetic force can also be used for the securing device and the coupled multicore wire armoured cable by appropriate design choice. For example, the weight of the device may be designed to be less than the magnetic force generated when the multi-core wire-armoured cable is housed in this area.

The apparatus may also include structure supporting the one or more magnets and the one or more magnetic field sensors. The structure may include a channel configured to receive a multi-core wire-armored cable. In other words, the structure may be a channel defining structure. The cross-section of the channel may have a circular or circular arc shape. The cross-section of the channel may have a shape that is non-circular and does not correspond to an arc of a circle. The channel may be open to accommodate a multi-core wire-armoured cable. The structure may define the cross-section of the channel as a C-shape or a U-shape. The cross-section may be taken in a plane perpendicular to a direction corresponding to an axial direction of the channel along which the multi-core wire-armored cable is to be received when the multi-core wire-armored cable is coupled to the device.

The channel may be defined by first and second components of the structure configured to encase the multi-core wire-armored cable when the multi-core wire-armored cable is received within the channel. The first and second parts may be urged together by a spring. The first and second components may be urged by magnetic force from at least some of the one or more magnets to encase the closed multi-core wire-armoured cable. The first and second parts of the structure may provide a clamp. Once the multi-core wire armored cable is encased, the first and second components may be secured together by a latch, catch or similar fastening means.

The structure may include or take the form of two or more components configured to encase a closed or wound multi-core wire-armoured cable to define a channel. The two or more components may be urged together by a spring. Once wrapped around the multi-core wire-armored cable, the two or more components may be secured together by one or more latches, catches, or similar fastening devices.

The apparatus may further comprise a net current sensor configured to measure a net current through the multi-core wire-armoured cable when the apparatus is coupled to the multi-core wire-armoured cable. The net current sensor may comprise or take the form of a rogowski coil. The net current sensor may comprise or take the form of a current transformer. One or more magnetic field sensors may be disposed within the transformer coil of the current transformer.

At least one of the one or more magnetic field sensors may comprise or take the form of a coil. Each coil may be wound on a sense pole piece. Two or more of the magnetic field sensors may be provided by respective coils. Two or more coils providing a magnetic field sensor may be wound on respective portions of a single sense pole piece. Or two or more coils providing a magnetic field sensor may be wound on respective separate sense pole pieces.

The circumferential sensing pole piece may extend around all or part of the circumference of the multi-core wire-armored cable when the multi-core wire-armored cable is received, and may include two or more inward radial projections. A coil providing a magnetic field sensor may be wound around each inward radial protrusion.

At least one of the one or more magnets may comprise or take the form of an electromagnet. Each electromagnet may be wound on a pole piece. Two or more of the magnets may be provided by electromagnets. Two or more electromagnets may be wound on respective portions of a single pole piece. Or two or more coils providing a magnetic field sensor may be wound on respective individual pole pieces.

The device may include a common pole piece having one or more coils providing a magnetic field sensor wound on a respective portion and one or more electromagnets wound on other portions.

The device may comprise two or more magnetic field sensors. The device may comprise three or more magnetic field sensors. The device may comprise four or more magnetic field sensors. The device may comprise five or more magnetic field sensors. The device may comprise six or more magnetic field sensors. The device may comprise ten or more magnetic field sensors.

The magnetic field sensors may be positioned at equiangular intervals around the channel housing the multi-core wire-armoured cable.

The one or more magnets may include or take the form of a first set of magnets including a plurality of first magnets and a second set of magnets including a plurality of second magnets. When coupled to the device, the first set of magnets and the second set of magnets may be positioned to both sides of the one or more magnetic field sensors in a direction corresponding to an axial direction of the multi-core wire armored cable. In other words, the first set of magnets and the second set of magnets may clamp the magnetic field sensor or sandwich the magnetic field sensor along the length of the coupled/received multi-core wire armored cable.

The apparatus may include a pair of magnets corresponding to each magnetic field sensor. Each pair of magnets may be arranged to both sides of the corresponding magnetic field sensor in a direction corresponding to the axial direction of the multi-core wire-armoured cable (when coupled to the apparatus). In other words, each pair of magnets may clamp or sandwich a corresponding magnetic field sensor along the length of the coupled/received multi-core wire-armored cable.

The one or more magnetic field sensors may include a first set of first magnetic field sensors and a second set of second magnetic field sensors. The first set of magnetic field sensors and the second set of magnetic field sensors may be arranged to be spaced apart along an axial direction of the multi-core wire-armoured cable (when coupled to the apparatus).

In this way, differences in magnetic field measurements made using the first set of magnetic field sensors and the second set of magnetic field sensors may be used to compensate for different twist rates (TWISTING RATE) between different multi-core cables, as further discussed with respect to the apparatus of the third aspect.

The sensor may comprise the apparatus of the first aspect and a controller. The controller may be connected to one or more magnetic field sensors and configured to calculate one or more derived quantities for part or all of the cores of the multi-core wire-armoured cable based on magnetic field components measured by the magnetic field sensors.

The one or more derived quantities may include, but are not limited to, current in each core (the core current may be alternating differential current or direct differential current between cores), phase between cores, harmonics, time domain current in one or more individual cores, number and/or geometry of cores within a multi-core wire-armoured cable, or cores/conductors within a magnetically soft pipe or conduit or cable bridge (tray), etc.

At least a portion of the device containing at least one sensor may be moved relative to the core or conductor of interest to provide additional data to enable improved determination of the derived quantity. At least one sensor may be moved between two defined positions relative to the conductor of interest to provide additional magnetic field data to determine the geometry and other derived quantities of the current carrying conductor.

Two or more turns of the magnetic field sensor may be axially spaced apart. Additionally or alternatively, one or more of the turns may be offset from the central axis of the sensor assembly, thereby providing additional magnetic field data to determine the geometry of the current carrying conductor/core and other derived parameters.

The magnetic sensor array may be arranged at the time of measurement in any predetermined geometry, such as a ring, a two-piece clamp, or a clamshell, or any shape used by conventional single current probes, or a fixed or open rectangle (suitable for conductors arranged in rectangular tubing or cable bridge sections), or an oval (fixed or open), or an open shape such as a "C" shape or a "U" shape, or a self-returning shape. During the measurement process, the relative position of the sensor must not change.

The described apparatus and methods may also be applied to cores, cables or conductors grouped together but not necessarily housed in a single multi-core cable.

The steel wire armored multi-core cable is a subset of multi-core cables.

The described apparatus and method may be used to saturate portions of magnetically conductive steel or soft magnetic (conductor-containing conduit or pipe or cable) portions.

The one or more magnets and the one or more magnetic field sensors may be mounted within a soft magnetic housing or a channel defining structure. The soft magnetic channel defining structure provides magnetic immunity to external current carrying conductors near or adjacent to the device.

If no magnets are used, the channel defining structure may be made of a non-magnetic (i.e., non-magnetically permeable) material. If magnets are used, the channel defining structure may be made of a non-magnetic (i.e., non-magnetically permeable) material. If magnets are used, the channel defining structure may be made of a magnetic (i.e., magnetically permeable) material.

Magnetic immunity may be achieved using a magnetic field sensor. For example, the magnetic field sources inside the multi-core cable are distinguished from external magnetic field sources by using the known relative positions and orientations of the magnetic field sensors.

The controller may include one or more digital electronic processors communicatively coupled to a memory. The controller may include a store holding computer program code that, when executed by one or more digital electronic processors, implements one or more of:

● The controller obtains magnetic field measurements using one or more magnetic field sensors;

● The controller controls the energizing state of the one or more electromagnets;

● The controller calculates one or more derived quantities.

The computer program may be an algorithm or a series of algorithms. The computer program may operate on the same principles as the cited prior art and/or may use a series of principles developed as follows:

The derived amount being immune to external magnetic fields (e.g. caused by adjacent current carrying conductors outside the sensor), and/or

Leaving the calculation of the derived quantity unaffected by the core twist (twist) associated with the multicore cable

The sensor may comprise the apparatus of the first aspect. The apparatus may also be configured to generate one or more signals based on the output of the one or more magnetic field sensors. Each signal may be proportional to a differential current between the cores of the multi-core wire-armoured cable (when coupled to the apparatus). Each signal may be proportional to a respective core current of a respective core of the multi-core cable. The sensor may also include a link corresponding to each signal for connection to a control and/or measurement system.

Some or all of the links may take the form of wired links. Some or all of the links may take the form of low power wireless links (e.g., bluetooth (RTM), RFID, etc.).

Any of the sensors may also include one or more voltage sensors, and the one or more derived quantities may include one or more power values. The one or more power values may include power delivered by each core and/or total power delivered by the multi-core wire-armored cable.

The system may include any sensor coupled to provide input to the measurement device. The measurement device may receive one or more derived quantities from the sensor. The measurement device may receive one or more signals based on the output of the one or more magnetic field sensors.

The measurement device may be a power quality analyzer. The power quality analyzer may also be referred to as a "power quality monitor".

The measurement device may be a power quality recording device. The power quality recording device may take the form of a power recorder or an energy recorder.

According to a second aspect of the present invention there is provided a method comprising coupling a device according to the first aspect to a multicore wire armored cable, or coupling a device comprised by a sensor or system to a multicore wire armored cable, such that a magnetic field corresponding to one or more magnets is applied to an area of the multicore wire armored cable. The method further includes measuring a magnetic field component originating from the region of the multi-core wire-armoured cable using one or more magnetic field sensors.

The magnetic field corresponding to the one or more magnets may saturate the steel wire armor magnetic field in that region. The magnetic field corresponding to the one or more magnets may magnetically saturate (all or part of) the steel wire armor in that region.

The permeability of a magnetic material such as steel wire armor may be defined as the gradient of magnetic flux with magnetic field, i.e.:

wherein mu is the magnetic permeability of the steel wire armor layer, B is the magnetic flux (unit is Tesla, T), and H is the magnetic field strength (unit is ampere/meter, A.m ^-1).

If the permeability μ is less than or equal to 20% of the peak value, the magnetic field in the steel wire armor may be considered saturated. If the permeability μ is less than or equal to 15% of the peak value, the magnetic field in the steel wire armor may be considered saturated. If the permeability μ is less than or equal to 10% of the peak value, the magnetic field in the steel wire armor may be considered saturated. If the permeability μ is less than or equal to 5% of the peak value, the magnetic field in the steel wire armor may be considered saturated.

Or when the same current is supplied via the core of each cable in each case, the magnetic field in the wire armor may be considered saturated if the decay of the magnetic field measured by the one or more magnetic field sensors does not exceed 10% compared to a multi-core cable which is identical to a multi-core wire armor cable system except that the wire armor is omitted.

The method may further comprise calculating one or more derivative quantities for part or all of the core of the multi-core wire armoured cable based on the magnetic field component measured by the magnetic field sensor. The one or more derivative amounts may include, but are not limited to, current in each core, differential current between cores, phase between cores, harmonics, time domain current in one or more individual cores, number and/or geometry of cores within a multi-core wire-armoured cable, etc.

The method may comprise features corresponding to any features of the apparatus of the first aspect and/or of a sensor or system comprising the apparatus of the first aspect (and/or features thereof). The definition of a sensor or system applicable to and/or comprising the apparatus of the first aspect (and/or features thereof) may equally apply to the method of the second aspect (and/or features thereof).

According to a third aspect of the present invention, there is provided an apparatus for coupling to a multi-core cable. The apparatus includes a first set of one or more first magnetic field sensors. The apparatus also includes a second set of one or more second magnetic field sensors. The apparatus is configured such that when the apparatus is coupled to the multi-core cable, each first magnetic field sensor is oriented to detect a magnetic field component originating from a first region of the multi-core cable. The apparatus is configured such that when the apparatus is coupled to the multi-core cable, each second magnetic field sensor is oriented to detect a magnetic field component originating from a second region of the multi-core cable. The apparatus is configured such that when the apparatus is coupled to the multi-core cable, the first region is spaced apart from the second region along a length of the multi-core cable.

The apparatus of the third aspect may include features corresponding to any features of the apparatus of the first aspect and/or the method of the second aspect (and/or features thereof). The definition applicable to the apparatus of the first aspect and/or the method of the second aspect (and/or the features thereof) may equally be applied to the apparatus of the third aspect (and/or the features thereof).

When coupled to the multi-conductor cable, the number and arrangement of the first magnetic field sensors relative to the multi-conductor cable may be the same as the number and arrangement of the second magnetic field sensors relative to the multi-conductor cable.

The individual cores of a multi-core cable are typically twisted with one another to increase the mechanical compliance of the cable as a whole and to facilitate cabling, winding, etc. When the measurement of the magnetic field generated by the wire cores is used for the purpose of inferring the current in the wire cores and/or the relative phase between the wire cores, some assumptions need to be made about the relative positions and twist rates of the wire cores. However, if an unknown cable is measured, such geometric factors are not available without disassembling the cable and without violating the purpose of non-invasive measurement. With the arrangement of the third aspect, the relative position of each wire core will vary between the first set of magnetic field sensors and the second set of magnetic field sensors, while the current remains unchanged between the first region and the second region. In this way, differences in magnetic field measurements obtained using the first set of magnetic field sensors and the second set of magnetic field sensors may be used to compensate for different twist rates between different multi-core cables. For example, the magnetic field measurement rotation rate detected by the magnetic field sensor may be related to the twist/rotation rate of the core of the multi-core cable.

The apparatus of the third aspect may further comprise one or more magnets arranged such that when the apparatus is coupled to the multi-core cable, a magnetic field corresponding to the one or more magnets is applied to the first and second regions of the multi-core cable.

The magnetic fields corresponding to the one or more magnets may be applied substantially equally to the first region and the second region of the multi-core cable. Substantially equal may refer to the magnetic fields in the first and second regions being approximately symmetrical about a mirror plane equidistant between the first and second regions and oriented perpendicular to the axial direction of the multi-core cable (when coupled). Approximate symmetry may refer to the magnetic field components (e.g., x, y, z components) at any point in the first region differing by no more than 10% from the reflection points in the second region.

According to a fourth aspect of the present invention, there is provided an apparatus for coupling to a multi-core cable, the apparatus comprising a current transformer coil and one or more magnetic field sensors. The apparatus is configured such that when the apparatus is coupled to a multi-core cable, a region of the multi-core cable passes through the current transformer coil. The apparatus is configured such that, when the apparatus is coupled to the multi-core cable, the one or more magnetic field sensors are disposed at least partially between the core of the current transformer coil and the multi-core cable. At least one of the magnetic field sensors is oriented to detect a magnetic field component originating from the region of the multi-core cable.

The current transformer coil may also be referred to as a "CT" coil. The current transformer coil may be configured to measure a net current flowing through the multi-core cable. The one or more magnetic field sensors may be arranged and configured to measure one or more derived quantities for part or all of the core of the multi-core cable based on the magnetic field components measured by the magnetic field sensors. These derived quantities may include any or all of the derived quantities specified in relation to the apparatus according to the first aspect and/or the method according to the second aspect.

The apparatus according to the fourth aspect may comprise features corresponding to any of the features of the apparatus according to the first and/or third aspects. The definition applied to the apparatus (or feature thereof) according to the first and/or third aspect may equally apply to the apparatus (or feature thereof) according to the fourth aspect.

The current transformer coil may be shorted via a resistor. This resistance may sometimes be referred to as a "shunt resistor," load resistor, "or" load resistance. The resistance may be between 0.1 Ω and 100 Ω. Preferably, the resistance may be between 1 Ω and 10 Ω. The voltage measured across the "load resistor" is proportional to the net current through the multi-core conductor of the current transformer coil.

The one or more magnetic field sensors may be disposed at least partially within an inner diameter of the current transformer coil.

The core of the current transformer coil may comprise or take the form of magnetically permeable material. The magnetically permeable material may be soft iron. The current transformer coil can be directly wound on the magnetic core of the magnetic conductive material. The current transformer coil may be wound on a former (or similar support) and one or more regions of magnetically permeable material may be housed in the former (or similar support). For example, a current transformer coil may be wound on a former having a through hole, and a magnetic permeable material core may be inserted into the through hole so as to be disposed within the current transformer coil.

The skeleton may be flexible and/or segmented. In this manner, the current transformer coil may be wound on the former in a flat configuration, and then the former may be bent and/or folded to form a toroidal shape (or a portion thereof).

The current transformer coil may comprise or take the form of two or more sub-coils. The two or more sub-coils may be connected together. Two, a subset or all of the sub-coils may be connected in series. Two, a subset or all of the sub-coils may be connected in parallel.

The apparatus may be configured such that the region of the multi-core cable received by the current transformer coil is oriented in an axial direction. The current transformer coils may extend in an axial direction on both sides of the one or more magnetic field sensors. The magnetic core of the current transformer coil may extend in the axial direction on both sides of the one or more magnetic field sensors.

The length of the current transformer coil extending in the axial direction may be greater than or equal to half of the inner diameter of the current transformer coil. The length of the current transformer coil extending in the axial direction may be greater than or equal to the inner diameter of the current transformer coil. The length of the current transformer coil extending in the axial direction may be greater than or equal to twice the inner diameter of the current transformer coil. The one or more magnetic field sensors may be disposed at a midpoint along the length of the current transformer coil in the axial direction.

At least one of the one or more magnetic field sensors may comprise or take the form of a sensor coil. Each sensor coil may be wound on a sense pole piece. Each sensor coil may be wound on a portion or protrusion of the core of the current transformer coil. Two or more of the magnetic field sensors may comprise or take the form of respective sensor coils. All of the one or more magnetic field sensors may comprise or take the form of respective sensor coils. The sensor coil may be prefabricated with the multicore cable inserted therein, or wound in situ around the multicore cable, or connected in situ around the multicore cable, or placed in situ around the multicore cable. The sensor coils may be mounted radially, tangentially or along other axes relative to the longitudinal axis of the device along which the multi-core cable is configured to be received. A mixture of sensor coil orientations may be used, such as, but not limited to, radial and tangential within a single device. The sensor coil may be wound on a magnetic core of magnetically permeable material. The sensor coil may be a so-called "air core" coil, which does not comprise a magnetic core of magnetically permeable material. The "air core" sensor coil may be wound on a support structure formed of a non-magnetically permeable material (e.g., plastic, glass, etc.). The sensor coil may be wound on the former. The armature may be shared with a current transformer coil.

The apparatus may include a structure supporting the current transformer coil and the one or more magnetic field sensors. The structure may include or take the form of a former upon which the current transformer coil and/or one or more sensor coils are wound. When one or more magnets are included in the device, the structure may also support the one or more magnets.

The structure may include a channel configured to receive a multi-conductor cable. In other words, the structure may take the form of a channel defining structure.

The cross-section of the channel may have a circular or circular arc shape.

The cross-section of the channel may have a shape that is non-circular and does not correspond to an arc of a circle.

The channel may be open. The open channel may accommodate a multi-conductor cable. The structure may define the channel as self-returning in cross section. The structure may define the channel as C-shaped or U-shaped in cross-section. The cross-section may be taken in a plane perpendicular to a direction corresponding to an axial direction of the channel along which the multi-core cable is to be received when the multi-core cable is coupled to the device.

The channel may be defined by first and second components of the structure configured to encase the multi-conductor cable when housed within the channel. The first and second parts may be urged together by a spring. The first and second parts of the structure may provide a clamp. Once the multi-conductor cable is wrapped closed, the first and second components may be secured together by a latch, catch, or similar fastening device.

The structure may include two or more components configured to encase a closed or wrapped multi-core cable to define a channel. The two or more components may be urged together by a spring. Once the multi-conductor cable is wrapped closed, the two or more components may be secured together by one or more latches, catches, or similar fastening devices. The structure may be segmented in that two or more components may be joined together by a flexible material or joined together using a hinge aligned with the axial direction.

The device may comprise two or more magnetic field sensors.

The device may also include one or more magnets. The apparatus may be configured such that when the apparatus is coupled to the multi-core cable, a magnetic field corresponding to the one or more magnets is applied to a region of the multi-core cable passing through the current transformer coil.

In this way, the device according to the fourth aspect can be applied to a wire-armored multi-core cable in the same manner as the device according to the first aspect, and the same effects and advantages are obtained.

The one or more magnetic field sensors may include a first set of first magnetic field sensors and a second set of second magnetic field sensors. The first set of magnetic field sensors and the second set of magnetic field sensors may be arranged to be spaced apart along an axial direction of the multi-core cable (when coupled to the device).

The sensor may comprise an apparatus according to the fourth aspect. The sensor may also include a controller coupled to the one or more magnetic field sensors. The controller may be configured to calculate one or more derived quantities for part or all of the cores of the multi-core cable based on the magnetic field components measured by the magnetic field sensor.

The controller may be further configured to calculate a net current through the multi-core cable based on the measurement using the current transformer coil.

The one or more derived quantities may include, but are not limited to, current in each core (the core current may be alternating differential current or direct differential current between cores), phase between cores, harmonics, time domain current in one or more individual cores, number and/or geometry of cores within a multi-core cable, or cores/conductors within a magnetically soft conduit or pipe or cable bridge, etc.

The sensor may comprise an apparatus according to the fourth aspect. The apparatus may also be configured to generate one or more signals based on the output of the one or more magnetic field sensors. Each signal may be proportional to a differential current between the cores of the multi-core cable (when coupled to the device). Or each signal may be proportional to a respective core current of a respective core of the multi-core cable. The sensor may also include a link corresponding to each signal for connection to a control and/or measurement system. The apparatus including the sensor may be further configured to generate a net current signal based on the output from the current transformer coil.

The sensor may also include one or more voltage sensors. The one or more derived quantities may include one or more power values. The sensor may be configured to correctly assign phases to the core of the multi-core cable using one or more voltage sensors.

Using current transformer coils, the sensor can be powered by the net current through the multi-core cable.

The system may include the aforementioned sensor coupled to provide input to the measurement device. The measurement device may be a power quality analyzer. The measurement device may be a power quality recording device. The measuring device may be an energy meter. The measuring device may be an electricity meter.

According to a fifth aspect of the present invention there is provided a method comprising coupling a device (or a sensor/system incorporating the device) according to the fourth aspect to a multi-core cable such that a region of the multi-core cable passes through a current transformer coil. The method also includes measuring a magnetic field component originating from the region of the multi-core cable using one or more magnetic field sensors.

The method according to the fifth aspect may comprise features corresponding to any of the features of the apparatus according to the first, third and/or fourth aspects. The definitions applicable to the apparatus (or features thereof) according to the first, third and/or fourth aspects may equally apply to the method (or features thereof) according to the fifth aspect.

The method may further include measuring a net current through the multi-core cable using the current transformer coil.

According to a sixth aspect of the present invention, there is provided an apparatus for coupling to a multi-core cable, the apparatus comprising a rogowski coil and one or more magnetic field sensors. The device is configured such that when the device is coupled to the multi-core cable, a region of the multi-core cable passes through the rogowski coil, or the rogowski coil is wound on the region of the multi-core cable. At least one of the magnetic field sensors is disposed adjacent to the rogowski coil and oriented to detect a magnetic field component originating from the region of the multi-core cable.

At least one of the one or more magnetic field sensors may be disposed or at least partially disposed inside the inner diameter of the rogowski coil. In other words, in use, is disposed between the rogowski coil and the multi-core cable. At least one of the one or more magnetic field sensors may be disposed outside of the rogowski coil. In other words, separated from the multi-core cable by the rogowski coil. At least one of the one or more magnetic field sensors may be disposed adjacent to the rogowski coil in the axial direction.

The apparatus according to the sixth aspect may comprise features corresponding to any of the features of the apparatus according to the first, third and/or fourth aspects. The definition applicable to the apparatus (or feature thereof) according to the first, third and/or fourth aspects may equally be applied to the apparatus (or feature thereof) according to the sixth aspect.

Drawings

Certain embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional 3/4 view of a sensor assembly including two magnet arrays, a semiconductor magnetic sensor array, a housing channel defining structure, and associated electronics, connections and outputs, showing a length of armored multi-core cable for illustrative purposes.

FIG. 2 is a cross-sectional 3/4 view of a sensor assembly including two magnets, a semiconductor magnetic sensor array, and a housing channel defining structure, showing a length of armored multi-core cable for illustrative purposes.

FIG. 3 is a cross-sectional view of a sensor assembly including a housing, two magnet arrays, a semiconductor type magnetic sensor array mounted on a soft magnetic mounting ring, and a housing channel defining structure.

FIG. 4 is a cross-sectional 3/4 view of a sensor assembly including a housing, two magnet arrays, a tangential coil magnetic sensor array, a housing channel defining structure, and associated electronics and outputs.

FIG. 5 is a cross-sectional 3/4 view of a sensor array including a soft magnetic ring, a plurality of axial sensor coils, and their associated outputs.

Fig. 6 is an isometric view of a sensor assembly specifically configured as a multi-phase electric meter including a sensor assembly, an associated electronics housing having a display and a service port, a load under test, a phase connection from the electronics housing to the load under test, and a length of armored multi-core cable (for illustrative purposes).

Fig. 7 is an isometric view of a sensor assembly specifically configured as a power quality analyzer including a sensor assembly, a power meter, a phase connection to a device under test, and a set of three rogowski coils to illustrate an alternative method-the armored multi-core cable under test is not shown.

Fig. 8A and 8B are isometric axial and cross-sectional views, respectively, of a sensor assembly including two magnet arrays, a radial coil magnetic sensor array mounted on a soft magnetic mounting ring, and a housing channel defining structure.

Fig. 9A and 9B are isometric axial and cross-sectional views, respectively, of a sensor assembly including two magnet arrays, radial and tangential coil-type magnetic sensor arrays mounted on a soft magnetic mounting ring, and a housing channel defining structure.

Fig. 10A and 10B are isometric axial and cross-sectional views, respectively, of a sensor assembly including two magnet arrays, a radial coil magnetic sensor array mounted on a soft magnetic mounting ring, and a housing channel defining structure with two additional radial coils on either side of the soft magnetic mounting ring.

FIG. 11 is an isometric cross-sectional view of a sensor assembly including two magnet arrays, two radial coil magnetic sensor arrays mounted on respective soft magnetic mounting rings, and a housing channel defining structure.

Fig. 12A, 12B and 12C are respectively isometric axial, side and isometric cross-sectional views of an open sensor assembly including two magnet arrays, a radial coil magnetic sensor array mounted on a soft magnetic mounting ring, and a mounting channel defining structure and housing showing a length of armored multi-core cable set resting on a flat surface for illustrative purposes.

Fig. 13A, 13B and 13C are respectively an isometric cross-sectional view (open), an isometric view (closed) and an isometric cross-sectional view (open) of a 'spring-clip' sensor assembly comprising two magnet arrays, a radial coil magnetic sensor array mounted on a soft magnetic mounting ring, a mounting channel defining structure and a housing assembly with springs, for illustrative purposes, showing a length of armored multicore cable.

Fig. 14B, 14B and 14C are respectively an isometric cross-sectional view, a plan cross-sectional view and an isometric view of a sensor assembly including two magnets, radial sensor coils, a soft magnetic backing member and a wired connection, showing a length of armored multi-core cable for illustrative purposes.

15A, 15B, 15C, 15D and 15E are respectively an isometric view (open), an isometric view (closed), a side view (closed), an isometric axial cross-sectional view (closed) and an isometric cross-sectional view of a multi-unit sensor assembly, each individual unit of which includes two magnets, radial sensor coils, a soft magnetic backing sheet, a hinge element and a movement limiting element, for illustrative purposes, showing a length of armored multi-core cable.

FIGS. 16A, 16B and 16C are respectively an isometric view, an isometric cross-sectional view and an isometric axial cross-sectional view of a sensor assembly including a soft magnetic cylindrical sensor body, an electromagnetic coil and a radial coil type magnetic sensor array mounted on a soft magnetic mounting ring.

17A, 17B and 17C are respectively an isometric view, an axial cross-sectional view and a cross-sectional view of a sensor assembly including an electromagnetic coil, a soft magnetic armature, a hinge and/or clip type housing, and a radial coil type magnetic sensor array, showing a length of armored multi-core cable for illustrative purposes.

Fig. 18A, 18B and 18C are respectively an isometric cross-sectional view, a plan cross-sectional view and an isometric view of a sensor assembly including a magnet, radial sensor coils, a soft magnetic backing member and a wired connection, showing a length of armored multi-core cable set resting on a flat surface for illustrative purposes.

Fig. 19 shows a comparison of the current in a three conductor multi-core cable measured using the sensor assembly experiments shown in fig. 8A and 8B with measurements made by separating one of the conductors and using a conventional current clamp probe.

Fig. 20 shows the error obtained by analyzing the data shown in fig. 19 for a series of applied currents.

Fig. 21 and 22 show comparable data of fig. 19 for current signals with harmonic components up to 11 th order harmonics.

Fig. 21 and 22 show experimentally determined currents obtained using the same apparatus as fig. 19 for a current signal including a superposition of a fundamental frequency sine wave and 31 harmonics thereof.

Fig. 24A and 24B are isometric axial and cross-sectional views, respectively, of a sensor assembly that is a modification of the sensor assembly shown in fig. 9A and 9B.

Fig. 25A and 25B are an isometric view and an axial cross-sectional view of a sensor assembly including two channel defining structures that together form a ring. The solid state magnetic field sensor array is disposed around the inner surface of the ring.

Fig. 26A, 26B, 26C and 26D show an axial cross-section, an axial side view, an isometric view and a plan view, respectively, of a sensor assembly including sets of radial sensor coils disposed within a channel defining structure in the form of two semi-cylinders of magnetically permeable material. The magnets/magnet arrays are included at both ends and end caps of magnetically permeable material help complete the magnetic circuit outside the sensing volume.

Fig. 27A, 27B and 27C show plan, axial side and isometric views, respectively, of a skeletal device for use in the sensor assemblies of fig. 26A-26D.

Fig. 28A, 28B and 28C show plan, axial side and isometric views, respectively, of a magnet for use in the sensor assembly of fig. 26A-26D.

Fig. 29A, 29B and 29C show plan, axial side and isometric views, respectively, of an outer core for use in the sensor assembly of fig. 26A-26D.

Fig. 30A, 30B and 30C show plan, axial side and isometric views, respectively, of an end cap for use in the sensor assembly of fig. 26A-26D.

Fig. 31A and 31B show an isometric axial cross-section and an axial cross-section, respectively, of a sensor assembly comprising two magnet arrays and a tangential coil type magnetic sensor array mounted on a channel defining structure.

Fig. 32A, 32B, 32C, and 32D show an isometric view of a closed sensor array, an isometric view of an open sensor array, a plan view of a closed sensor array, and a plan view of a closed sensor array, respectively. The sensor array comprises a tangential coil-type magnetic sensor array mounted on a pair of channel defining structures forming an oval shape in cross-section.

Fig. 33A, 33B, 33C, and 32D show an isometric view of a closed sensor array, an isometric view of an open sensor array, a plan view of a closed sensor array, and a plan view of a closed sensor array, respectively. The sensor array comprises a solid-state magnetic sensor array mounted on a pair of channel defining structures forming an oval shape in cross-section.

34A, 34B, 34C, 34D and 34E illustrate an isometric view, an isometric axial cross-sectional view, an axial cross-sectional view, a plan view and a plan cross-sectional view, respectively, of a sensor assembly including two magnet arrays and a radial coil magnetic sensor array supported within a magnetically permeable core of a current transformer. The radial coil magnetic sensor is disposed around the protrusion of the current transformer core.

Fig. 35A and 35B show an isometric axial cross-section and a plan cross-section, respectively, of a sensor assembly comprising two magnet arrays and a radial coil magnetic sensor array supported within a magnetically permeable core of a current transformer. The radial coil type magnetic sensor is hollow.

Fig. 36A and 36B show an isometric view of a flat backbone assembly and an isometric view of the same backbone assembly rearranged into a curved configuration, respectively. Fig. 36C shows an isometric view of a semi-cylindrical core segment for passing through a skeletal assembly in a bent configuration.

Fig. 37A and 37B show plan and isometric views, respectively, of a sensor assembly having a solid state magnetic sensor array disposed within a transformer coil wound on a toroidal core of magnetically permeable material.

Fig. 38A and 38B show plan and isometric views, respectively, of a sensor assembly having a solid state magnetic sensor array disposed within windings of a transformer coil wound on a toroidal core of magnetically permeable material.

39A, 39B, 39C and 39D show an isometric view of a closed sensor array, an isometric view of an open sensor array, a plan view of a closed sensor array and a plan view of a closed sensor array, respectively. The sensor array comprises a solid-state magnetic sensor array mounted on a pair of channel defining structures forming an oval shape in cross-section. The channel defining structure is formed of magnetically permeable material and serves as a magnetic core for the current transformer coil.

Fig. 40A and 40B show an isometric view and an axial side view, respectively, of a sensor array housing a multi-conductor cable. The sensor array includes a rogowski coil adjacent to a radial coil magnetic sensor array.

Detailed Description

Hereinafter, like parts are denoted by like reference numerals.

Fig. 1 shows a first sensor assembly I comprising a soft magnetic housing 'channel defining structure' 1 made of laminated steel, sintered or bonded metal powder or any other suitable material, which partly or completely surrounds an armored multi-core cable 6 to be tested.

The first sensor assembly I is a device for coupling to a multi-core wire armored cable, but may also be used with non-armored multi-core cables. The first sensor assembly I is formed of one, two or more soft magnetic 'channel defining structure' sections of the housing, which may hinge downwardly diagonally along an axis parallel to the longitudinal axis of the first sensor assembly I to allow the sensor to open and close around the multi-core wire armoured cable 6. The armored multi-conductor cable 6 or the armored multi-conductor cable is composed of three-phase alternating current carrying wires 8, 9 and 10 which are armored by a 'cage' of a plurality of metallic non-carrying soft magnetic wires 7 which is built into the outer section of the multi-conductor cable 6. The first sensor assembly I is closed around the multi-core cable 6, partially or completely enveloping the multi-core cable 6 under test. Each end of the channel defining structure 1 has one or more magnets 2 and 3 (or arrays of magnets). At one end, the magnet 2 is polarized to north, with all north pointing inward from the array and toward the multi-core cable 6 under test. At the opposite end, all magnets 3 (e.g. forming a magnetic array) are polarized as south poles, again all poles pointing towards the multi-core cable 6 under test. The magnets 2 and 3 are concentric with the measured multi-core cable 6 and generate a magnetic field from north to south along the measured multi-core cable 6 (see also fig. 3, tag 107). This in turn saturates the region of the steel armor 7 section of the multi-core cable 6 where the first sensor assembly I is located. The magnetic field may also be generated by electromagnet coils mounted with the permanent magnets 2, 3 or instead of the permanent magnets 2, 3, partially or wholly.

The magnetic field sensor array 4 is mounted within the channel of the channel defining structure 1 between the two magnetic arrays 2 and 3. The magnetic field sensor array 4 is composed of a plurality of magnetic field sensors 5 aligned on the same axis. The magnetic field sensors 5 are all directed inward and concentric with the armored multi-core cable 6 to be measured, and the magnetic field sensors 5 are formed in a loop around the armored multi-core cable 6 to be measured. The first sensor assembly I uses a solid-state type sensor or a semiconductor type sensor (e.g., a hall sensor or a giant magnetoresistance sensor) mounted on a flexible PCB or a flexible circuit board in close contact with the housing 1 (or "channel defining structure"). The magnetic field sensor 5 is positioned against, adjacent to or in close proximity to the soft magnetic housing 1. The position of the magnetic field sensor 5 is such that the magnetic field sensor 5 is able to measure the magnetic field generated by the current in the cores 8, 9, 10 of the multi-core cable 6 in the cable region saturated by the magnets 2, 3.

The processing of the signals from the magnetic field sensor 5 is performed by a processor (or controller) 12, which processor (or controller) 12 may be integrated with the first sensor assembly I or separately wired 11 to the first sensor assembly I. The processor takes the form of an electronic enclosure housing a controller 12 electrically connected to the first sensor assembly I. The controller 12 processing the data may generate three different current signal outputs, one for each of the three discrete phases 13, 14, 15 in the multi-core cable 6 under test. The device in the form of the first sensor assembly I may be used with two-core, three-core, four-core, five-core, six-core or more core cables. The number of outputs 13, 14, 15 will be adjusted accordingly.

The electronic unit 12 (or "controller") may also include one or more connectors 16 for power, data, updates, and other utilities and in the form of USB or the like.

The first sensor assembly I may also be used with non-wire multi-core cables (e.g., cables with copper wire "armors," which may also serve as neutral or ground wires), or with cables without any "armors" (i.e., only conductive cores within a plastic sheath).

Fig. 2 shows a second sensor assembly II, which is similar in design and operation to the first sensor assembly I described in relation to fig. 1. The second sensor assembly II is likewise formed of one or two or more soft magnetic "channel defining structure" sections 21 having a sensor array 25, wherein one or more magnetic field sensors 24 encircle a sheathed wire strand 27 of a multi-core cable 26, the multi-core cable 26 having measured wires 28a, 28b, 28c. In this case, each end of the channel defining structure 21 has an axially magnetized ring magnet or section of ring magnets 20 and 23 instead of having magnet arrays 2, 3. Magnets 20 and 23 are positioned at both ends of the channel defining structure 21. The magnets 20 and 23 are oriented in the same direction with the north poles oriented in the same direction along the axis of the multi-core cable 26 under test. Thus, the two magnets 20 and 23 in the second sensor assembly II, which face each other laterally, are opposite in polarity. The two magnets 20 and 23 generate a north-to-south magnetic field 22, which magnetic field 22 in turn saturates the region of the section of steel armor 27 of the armored multi-core cable 26 being tested where the second sensor assembly II is located.

Fig. 3 shows a cross-sectional view of a third sensor assembly III, similar to the first sensor assembly I described with respect to fig. 1, comprising channel defining structures 102 and 103 housing magnets 105, 110, 109 and 104, wherein the magnetic poles are oriented north poles 105, 110 (radially outward) and south poles 104, 109 (radially outward) to generate magnetic fields 107, 108.

The third sensor assembly III differs in that a flexible circuit board or PCB 112 mounts the semiconductor or solid state magnetic sensors 106 and 111 and possibly other sensors (dispersed between 106 and 111 as shown in fig. 3) mounted on a ring 101 made of axially or radially stacked/wound laminated steel or some other soft magnetic material. Alternatively, the ring 101 may be made of ferrite, pressed, sintered, or a composite magnetic material. The ring 101 may be wide enough to accommodate the magnetic sensors 106, 111 and have separate components at each end of the channel defining structure 102 to accommodate the magnets or arrays 105, 110, 109 and 104, or the ring 101 may be wide enough to form the entire channel, eliminating the need for the channel defining structures 102 and 103.

Fig. 4 shows a fourth sensor assembly IV, similar to the first sensor assembly I described in relation to fig. 1, comprising a channel defining structure 1 housing magnets (or magnet arrays) 49a, 49b, wherein the poles are oriented north and south at opposite ends to generate a magnetic field in the armored multi-core cable 6 under test. As shown in detail in fig. 1, the processing of the signals from the magnetic sensors 41, 42, 43, 44, 45, 46, 47, 48 is performed by a controller 50, which controller 50 is integrated with the fourth sensor assembly IV or is separately wired to the fourth sensor assembly IV. The controller 50 may provide three different outputs 51, 52 and 53, one for each of the cores 8, 9, 10 in the multi-core cable 6 under test (not shown in fig. 4 for clarity). The controller 50 may include one or more connectors for power, data, updates, and other utilities and in the form of a USB or similar form 54.

The fourth sensor assembly IV differs from the first sensor assembly I in that a plurality of magnetic sensors in the form of sensor coils 41, 42, 43, 44, 45, 46, 47 and 48 are used, which are mounted tangentially around the multicore cable 6 to be measured in a ring-shaped form. The sensor coils 41, 42, 43, 44, 45, 46, 47, and 48 are mounted between magnets (or magnet arrays) 49a and 49 b. The sensor coils 41, 42, 43, 44, 45, 46, 47 and 48 may be replaced by solid state magnetic field sensors in sensors on flexible circuit board/PCB material.

Fig. 5 shows a fifth sensor assembly V which is similar to the third sensor assembly III shown in fig. 3, but uses a plurality of sensor coils 62 instead of semiconductor sensors 111 on flexible circuit board/PCB material 112, the plurality of sensor coils 62 being mounted radially around the armored multi-core cable 6 (not shown in fig. 5) to be tested in a ring-shaped form and between an array of magnets (e.g., those 104, 105, 109, 110 as shown in fig. 3). The sensor coil 62 is read using a connector 63, which connector 63 may be a twisted pair as shown, or may be a coaxial cable (or the like) to improve the rejection of interfering signals. The sensor coil 62 may comprise pole pieces 61 made of soft magnetic material or hollow core, which pole pieces 61 may be mounted on a support such as a plastic skeleton. The sensor coil 62 may be mounted on a soft magnetic ring 60, the soft magnetic ring 60 being composed of radially stacked/wound laminated steel or ferrite, pressed, sintered or composite magnetic material. Or the fifth sensor array V may be mounted directly in the channel formed by the channel defining structure of the sensor assembly (not shown, but similar to fig. 1).

Fig. 6 shows a sixth sensor assembly VI in the form of a power meter. Any version of the first to fifth sensor assemblies I to V described may be used, but are specifically configured as a multiphase meter with particular advantages of non-invasive assembly. This may be accomplished by combining the magnetic sensor assembly data obtained from the sensor assemblies 72 and 73 (disposed in the first and second halves 72 and 73, the first and second halves 72 and 73 being secured around the multi-core cable 79 under test, as shown) with additional monitoring of the phase voltages u, v and w (shown by reference numeral 71 in fig. 6). This would include the magnet and sensor assemblies 72, 73 mounted on the armored multi-core cable 79 being tested, and the connection 75 to the meter 74. The sensor assemblies 72, 73 may be similar (or identical) to any of the first to fifth sensor assemblies I to V shown and described in the previous figures (fig. 1 to 5), or may be variants using alternative sensors, magnets and magnetic materials. The meter 74 includes a display for meter readings and other related information 82. A flying lead (FLYING LEAD, pinout) 81 enables voltage inputs from phases u, v, w to meter 74. Flying lead 81 includes three conductors 80, each conductor 80 being connected to an exposed length 76 of a respective wire core 77 leading to housing 70. The armor strands 78 are stripped to allow for the attachment of the flying leads 81. The voltage inputs from phases u, v, w may help to properly distribute the current measured from the armored multi-core cable 79 to the correct core of the cable 79. The meter 74 may include one or more connectors for power, data, updates, and other utilities and take the form of USB or the like 83.

Fig. 7 shows a seventh sensor assembly VII in the form of a power quality analyzer. The sensor assembly magnetic sensor 87 will be mounted to the armored multi-core cable 6 (not shown in fig. 7) under test and may be used in combination with a power meter 91 as a power quality analyzer VII. Three flying leads 88, 89, and 90 are connected to the respective phases at load connection points (e.g., exposed length 76 as shown in fig. 6) to input the voltage of each phase (u, v, w) into the power quality analyzer VII.

The cost of this solution may be lower, the assembly may be simpler, as a set of three rogowski coils 84, 85 or 86 are used (shown for illustration only, not necessary if a sensor 87 is used). The use of rogowski coils 84, 85, 86 may require that the three phases (e.g., cores 8, 9, 10) of the armored multi-core cable 6 to be tested be separated from the armor (e.g., wires 7) and separated to allow sufficient space to attach each rogowski coil 84, 85, 86, thus increasing component cost and installation complexity-while using sensor assembly 87 may avoid these drawbacks.

In a modification of the seventh sensor assembly VII (not shown), the output of the magnetic sensor assembly 87 may be split into three outputs (not shown) which simulate the respective outputs of three current transformers or three rogowski coils (similar to 84, 85, 86) and applied to the respective cores 8, 9, 10 (when split from a multi-core cable). In this way, the three outputs (not shown) of the magnetic sensor assembly 87 may be connected to existing power meters or power quality analyzers whose design input signals are three rogowski coils (similar to 84, 85, 86) or current transformers.

Fig. 8A and 8B show an eighth sensor assembly VIII. The eighth sensor assembly VIII is similar to the sensor assembly I shown in fig. 1 and the sensor assembly V shown in fig. 5, but shows in more detail a plurality of radial field coils 115 (magnetic sensors) mounted to a ring 114, the ring 114 being made of axially or radially stacked/wound laminated steel rather than a semiconductor magnetic sensor mounted on a PCB/flex circuit board between the magnet arrays 117a and 117 b. Or the ring 114 may be made of ferrite, pressed, sintered, or composite magnetic material. The ring 114 may extend into the center of each radial field coil 115 to form a pole piece 116, or the ring 114 may be flush with the trailing edge of the coil 115 (i.e., tubular), in other words, the coil 115 may have an air core with the ring 114 of magnetic material located behind the air core. Alternatively, the radial field coils 115 may be mounted in the channel defining structure 113 without the need for an additional mounting ring of magnetic material.

Fig. 9A and 9B show a ninth sensor assembly IX. The ninth sensor assembly IX has a plurality of radial sensor coils 121 and a plurality of tangential sensor coils 122, which are positioned in a ring-shaped fashion around the multi-core cable 6 (not shown in fig. 9A and 9B) under test and between the magnet arrays 120a and 120B. The sensor coils 121, 122 and the magnet arrays 120a, 120b are supported by the channel defining structure 118. The sensor coils consist of the same row of tangential coils 122 and radial coils 121, may consist of alternating tangential coils 122 and radial coils 121 or of tangential coils 122 and radial coils 121 in any other pattern (e.g., two tangential coils, one radial coil, and vice versa, etc.). These coils may have air coils, may be integrated into a ring 119 of magnetic material (as shown in fig. 9A) (the ring 119 has radially extending protrusions to provide pole pieces/cores), have individual pole pieces (not shown) or be a combination of air core (not shown) and integrated/individual pole pieces (not shown).

Fig. 10A and 10B show a tenth sensor assembly X. The tenth sensor assembly X is comprised of magnets 128a and 128b (or arrays), sensor coils 124, and soft magnetic material 127, similar to some of the configurations described in the previous assemblies, but adds one or two additional magnetic sensors 125, 126 (or arrays) on either side of the main sensor array 124. These additional sensors 125 and/or 126 are used to detect the physical twist of the tested multi-core cable 6 (not shown in fig. 10A and 10B). If the cable under test does not have a soft magnetic sheath or armor, then magnets 128a and 128b are not needed. The soft magnetic material ring 127 is sandwiched by the passage defining structure 123 in the axial direction, and the magnets 128a, 128b and the additional magnetic sensors 125, 126 are supported by the passage defining structure 123. The magnetic sensor 124 is supported by the soft magnetic material ring 127 (or is integrally formed with the soft magnetic material ring 127).

Fig. 11 shows an eleventh sensor assembly XI. The eleventh sensor assembly XI is comprised of any of the magnets 131a, 131b and material configurations described herein, but has a secondary sensor array (or second sensor array) 130 in addition to the primary sensor array (or first sensor array) 129. Many features may be similar to sensor assembly VIII, but in this case with an additional looped sensor 130. Two axially spaced turns of magnetic field sensors 129 and 130 are used to detect the physical twist of three-phase conductors (e.g., cores 8, 9, 10) in the armored multi-core cable 6 or any multi-core cable (including non-armored multi-core cables) being tested.

Fig. 12A, 12B, and 12C illustrate a twelfth sensor assembly XII. The twelfth sensor assembly XII may be comprised of any of the magnets 132a, 132b, magnetic sensor 133, and soft magnetic material 137 configurations described herein, but the measurement (magnetic sensor 133) and array of magnetic sensors 132a, 132b form an open shape or U-shape, or similar shape that returns from without forming a closed loop. The open shape of the twelfth sensor assembly XII allows a conductor (e.g., multi-conductor cable 6) to be inserted and measured when the armored or unarmored multi-conductor cable 135 being tested is mounted against or near the plane 134. This may take the form of a handheld device 136 for quick deployment applications, or may take the form of a permanent or semi-permanent device.

Fig. 13A, 13B, and 13C illustrate a thirteenth sensor assembly XIII. The thirteenth sensor assembly XIII consists of any one of the magnets 138a, 138b (or arrays), magnetic sensor 139 and soft magnetic material (channel defining structure) 140 configurations described herein, but takes the form of a clamp on the device for quick attachment and easy movement from one armored or unarmored multi-core cable 141 to another. The thirteenth sensor assembly XIII is comprised of two channel-defining structural sections 142 and 143 having two channel-defining structural sections 142 and 143 mounted in dual-handle 'spring-grip' housings 145 and 146, wherein one or more springs 144 are compression springs, torsion springs, or any other suitable type of springs, and are positioned to hold the sensor array (i.e., channel-defining structural sections 142 and 143) closed when not opened by pinching handles 145, 146. One or more springs 144 may be supplemented or replaced or used with catches (not shown) at the open ends of the sensors (i.e., channel defining structural sections 142 and 143) to ensure complete closure of the thirteenth sensor assembly XIII in use.

Fig. 14A, 14B, and 14C illustrate a fourteenth sensor assembly XIV. The fourteenth sensor assembly XIV uses the same technique as detailed in the first sensor assembly I shown in fig. 1, but consists of a pair of magnets 150 and 151 (or alternatively one magnet and a feature made of soft material) and one or more magnetic sensors 152 mounted on a soft magnetic backing member 147 (or "structure"). The fourteenth sensor assembly XIV may consist of any of the magnet/sensor/material configurations described herein, but in the form of a simplified single sensor/coil/magnet, as a less costly and easy to assemble variant, or may be temporarily secured or held against the armored multi-core cable 149 under test.

The fourteenth sensor assembly XIV may be connected by a wire 148 to a sensing, monitoring, data recording or other device and/or may include some or all of the data processing electronics, either built-in or remote wired/wireless.

Fig. 15A, 15B, 15C, 15D, and 15E illustrate a fifteenth sensor assembly XV. The fifteenth sensor array XV is made of each of the simplified sensors 153, as described for the fourteenth sensor assembly XIV shown in FIGS. 14A-14C or similar thereto, but each of the simplified sensors 153 (e.g., the fourteenth sensor assembly XIV) are linked together using an integrated or separate hinge, clamp or other flexible engagement element 155 to form a flexible assembly to provide monitoring performance that is more closely similar to that of the first sensor assembly I shown in FIG. 1 and variations thereof by providing greater coverage around the circumference of the armored multi-conductor cable 154 being tested. Each simplified sensor 153 includes a magnet 157, 158 and a magnetic sensor 159. The fifteenth sensor assembly XV (or array) can be spring-loaded for quick attachment and can have stops closed with natural springs to form a circle 156 in order to minimize off-axis inaccuracy.

Multiple independent sensor modules 153 (simplified sensors) can be added or removed as needed to optimize the Inside Diameter (ID) of the sensor.

Similar to the fourteenth sensor assembly XIV detailed in fig. 14, each sensor may be connected to sensing, monitoring, data recording or other devices by wires (fig. 14b, 148), and/or may include some or all of the built-in or remote wired/wireless data processing electronics. Or the individual sensor outputs may be concentrated into a single electronics housing (fig. 1, 12) to process data from all of the sensors 153 in the fifteenth sensor array XV.

In a modification (not shown), the fifteenth sensor assembly XV (or array) can include more or fewer sensors than the six simplified sensors 153 shown in fig. 15A-15E. Further, the fifteenth sensor assembly XV (or array) after modification can be configured to use only additional or fewer number of segments and can use as many simplified sensors 153 as are needed to wrap a given multi-core cable 154. In some embodiments of such a modified fifteenth sensor assembly XV (or array), the operator may specify the number of reduced sensors 153 to use, for example, by providing input to a controller (not shown) or actuating a switch or similar element provided on each individual reduced sensor 153. Additionally or alternatively, a controller (not shown) may automatically determine the number of active reduced sensors 153, for example, by analyzing signals received from each reduced sensor. The inactive (or redundant) simplified sensor 153 will continue to wrap around the cable 154/unsettled from the cable 154 and therefore be omitted. The relative angle of each simplified sensor 153 is easily derived from the number of active sensors.

In another modification, the simplified sensors 153 may be connectable/disconnectable to each other. For example, mechanical and/or electrical connections are made between the simplified sensors 153 using clamps, connectors, and the like. In this way, an operator can easily add or remove the simplified sensor 153 to obtain the appropriate size. The number of simplified sensors 153 connected together can be automatically detected, in a particularly simple example by adding an additional connector in each simplified sensor 153 and connecting a resistor in series for each connector, so that the total resistance can be used to automatically determine the number of simplified sensors 153 in use. The relative angle of each simplified sensor 153 is easily derived from the number of active sensors.

Fig. 16A, 16B, and 16C illustrate a sixteenth sensor assembly XVI. The sixteenth sensor assembly XVI is a simplified, lower cost version of the first sensor assembly I shown in fig. 1 and/or other variations previously described. The sixteenth sensor assembly XVI is a one-piece sensor that is composed of a cylindrical body 161 (channel defining structure) and a magnetic sensor array 163 formed in a ring shape, the cylindrical body 161 being made of a soft magnetic material and having an electromagnetic coil wound around the outside of the magnetic pole 162. The magnetic sensor 163 may be a radial coil (as shown), a tangential coil, a semiconductor-type coil, or a solid-state coil, may be mounted on a separate soft magnetic ring (see fig. 3, 101), may be mounted directly on the cylindrical body 161, with or without separate poles, or may form an extension of the poles from the ring or cylindrical body 161. Designed to pass as a single unit onto the armored or unarmored multi-core cable 160 being tested. The electronics may be integrated with the sixteenth sensor assembly XVI or separate from the sixteenth sensor assembly XVI. If the armored cable is to be evaluated, a magnet (not shown) may be added to the sixteenth sensor assembly XVI.

Fig. 17A, 17B, and 17C illustrate a seventeenth sensor assembly XVII. Similar in operation to the sensor assembly I, II, VIII detailed in fig. 1, 2, and 8, but using the biasing electromagnetic coil 165 provides a magnetic field that saturates or substantially saturates the steel armor in the armored multi-core cable 170 under test. The electromagnetic coil 165 is axially mounted (or directly wound) on the soft magnetic armature 167 by means of the soft magnetic armature 167 to cause a magnetic field around the armored multi-core cable under test. The armature 167 extends toward the armored multi-core cable 170 at both poles and surrounds the armored multi-core cable 170, and on both sides of the sensor array, the armature 167 is housed in a hinged housing 168 and/or a clip housing 169, allowing fitting around the armored multi-core cable 170.

The magnetic sensor may be of any of the types described in the specification-an axial or tangential coil 166 as shown or a semiconductor type coil, with or without magnetic material behind it, and with or without pole pieces.

Fig. 18A, 18B, and 18C illustrate an eighteenth sensor assembly XVIII. The eighteenth sensor assembly XVIII is a simplified sensor similar to the fourteenth sensor assembly XIV detailed with respect to fig. 14A-14C, but is comprised of a single magnet or magnetic field source 174 and a magnetic sensor 175. The eighteenth sensor assembly XVIII may consist of any of the magnet/sensor/material configurations described herein, in this example, using a permanent magnet and sensor coils on a soft magnetic backplate/bracket 173 (or "structure"). The eighteenth sensor assembly XVIII may be pressed against, secured to, or coupled to the armored or unarmored multi-conductor cable 171 being tested (e.g., secured in place by a magnet or magnetic field source 174 when the multi-conductor cable 171 is armored with steel).

This lower cost variation (eighteenth sensor assembly XVIII) may be coupled by a wired connection 172 to connect to sensing, monitoring, data recording or other devices, and/or may include some or all of the built-in or remote wired/wireless data processing electronics.

Referring additionally to fig. 19 and 20, the linearity of the sensor assembly described herein was evaluated. An example of the eighth sensor assembly VIII is applied to a 30 mm diameter three-core wire-armored multi-core cable. The inner diameter of the channel of the eighth sensor assembly VIII is 42 mm. Fig. 19 shows the current of each of three cores (solid line, broken line, and dash-dot line) measured using the example of the eighth sensor assembly VIII. The dashed line shows the current measured using a conventional current clamp applied directly to a second wire core, which is separate from the multi-core cable and the wire armor, at a point offset from the example of the eighth sensor assembly VIII. The consistency is still observed to be very accurate despite the presence of the steel wire armour layer.

The current of the eighth sensor assembly VIII used ranges from about 40mA up to 500A. The eighth sensor assembly VIII was tested at 25mA to 80A and the measured% error is plotted in fig. 20.

Referring additionally to fig. 21 and 22, data for a case of a signal having a higher harmonic component similar to fig. 20 is shown. In particular, core 1 applies a square wave, while cores 2 and 3 apply a triangular wave. All waveforms include components up to 11 harmonics. The solid line, the broken line, and the dash-dot line show the first core current, the second core current, and the third core current measured using the example of the eighth sensor assembly VIII. In fig. 21, the dashed line shows the measurement results obtained using a conventional current clamp probe applied to the wire core 2 (which is separated from the multi-core cable and the wire armor) at a position offset from the example of the eighth sensor assembly VIII. Fig. 22 is identical except that a conventional current clamp probe is applied to the wire core 1 instead of the wire core 2. In fig. 21 and 22, good agreement is obtained between the example of the eighth sensor assembly VIII and conventional measurements (requiring physical disassembly of the multi-core cable assembly), even with wire armor.

Referring additionally to fig. 23, data is shown similar to fig. 20, 21 and 22 for the case of a three-phase current having a signal of a fundamental sine wave of amplitude 20A superimposed with 31 th order harmonics of amplitude 2A. In this case, a broken line representing the measurement result of the conventional current clamp is obtained from the wire core 2. Even at 31 th harmonic, the example using the eighth sensor assembly VIII achieves good consistency with conventional measurement methods (which have the disadvantage of requiring physical splitting of the multi-core cable).

Fig. 24A and 24B show a nineteenth sensor assembly XIX. The nineteenth sensor assembly XIX is identical to the ninth sensor assembly IX except that the magnetic material ring 119b and tangential sensor coil 122b are reconfigured in a manner that can improve efficiency. In particular, the tangential sensor coils 122 of the ninth sensor assembly IX are disposed entirely within the inner radius of the channel defining structure 118, and to accommodate the tangential sensor coils 122, the magnetic material ring 119 of the ninth sensor assembly IX includes a "kink (kinks)" corresponding to each tangential sensor coil 122, wherein the ring 119 is turned radially inward to pass through the windings of the tangential sensor coils 122. This may be disadvantageous in terms of the flux path within transfer ring 119. In contrast, in the nineteenth sensor assembly XIX, the magnetic material ring 119b has a simpler shape without "kinking". The tangential sensor coil 122b is partially wound on the ring 119b, wherein the coil is partially disposed inside the channel defining structure 118 and partially disposed outside the channel defining structure 118. In this way, the tangential magnetic flux may follow an uninterrupted circular path around the ring 119 b. The radial sensor coil 121 remains wrapped around the inward radial projection of the ring 119b in the same manner as the ninth sensor assembly IX, and may be wrapped directly around the projection, or may be wrapped around a backbone housed on the projection.

Fig. 25A and 25B show a twentieth sensor assembly XX. The twentieth sensor assembly XX is similar to the first through third sensor assemblies I, II, III, except that the twentieth sensor assembly XX is formed more compactly along the length of the multi-core cable (which may be an armored or non-armored multi-core cable 160). The twentieth sensor assembly XX has a first channel-defining structure 180 and a second channel-defining structure 181 joined together around an armored or unarmored multi-core cable 160. The first and second channel defining structures 180, 181 may be formed of a magnetic material (e.g., silicon steel), but need not be. The inner surfaces of the channel defining structures 180 and 181 support the solid state magnetic sensor 182 directly or via a flexible circuit board or PCB. The longitudinal ends of the channel-defining structures 180, 181 include respective lips 183a, 183b, 184a, 184b that extend radially inward a distance at least equal to the height of the solid-state magnetic sensor 182. The twentieth sensor assembly XX is shown with six solid state magnetic sensors 182 arranged at 60 degree intervals around the circumference to form a hexagonal arrangement, but more or fewer solid state magnetic sensors 182 may be used and/or the angular spacing may be different or irregular.

The twentieth sensor assembly XX may be used as shown for an unshielded multi-core cable 160. For use with the armored multi-core cable 6, magnets (not shown in fig. 25A and 25B) should be added. The magnets may be discrete or annular and may be received on the inner surfaces of the channel defining structures 180, 181 and/or lips 183a, 183b, 184a, 184 b. In some examples, the lips 183a, 183b, 184a, 184b may be formed using ring magnets.

Referring additionally to fig. 26A-30C, a twenty-first sensor assembly XXI is shown. The twenty-first sensor assembly XXI is similar to the eighth sensor assembly VIII in that the assemblies are specifically designed to achieve compact, efficient and cost-effective manufacture.

Fig. 26A to 26D show an assembled twenty-first sensor assembly XXI. Fig. 27A-27C show a skeleton arrangement 185 in the form of a semi-circular support 186, from which semi-circular support 186 three skeletons 187 extend radially inwards. Preferably, the armature 187 is integrally formed with the semi-circular bracket 186 using injection molded plastic. Or the backbone 187 may be separately formed and attached to the semicircular bracket 186. The skeletons 187 are spaced 60 degrees apart from each other (about 30 degrees apart from either end) about the semicircular brackets 186. Each half of the twenty-first sensor assembly XXI comprises a skeleton device 185, forming a ring around the multi-conductor cable 6, 160 as a whole. Each armature 187 has a radial sensor coil 188 wound thereon. For example, each radial sensor coil 189 may be formed from 300 turns of enameled copper wire having a diameter of 0.25 millimeters. Although shown as an air coil in fig. 26A-26D, in some examples, a magnetic core material may be inserted into the through-holes of each armature 187 (either before or after winding the sensor coil 188).

The bobbin device 185 formed with windings of the sensor coil 188 is housed in a first outer core 189A and a second outer core 189b (shown in fig. 29A to 29C, respectively). Each outer core 189a, 189b is a half cylinder formed of a magnetic material (e.g., wound silicon steel tape) suitable for use in a transformer. Preferably, the first outer core 189a and the second outer core 189b are formed by bisecting a cylindrical body of wound silicon steel strip. Pairs of magnets 190a and 190b are also housed within each outer core half 189a, 189 b. A single magnet 190 is shown in fig. 28A-28C. The magnets 190a, 190b may be magnetized ferrite, such as C5 ferrite used in speakers. The magnets 190a, 190b may be magnetized to provide a magnetic field substantially along a longitudinal axis, as in the second sensor assembly II, or may have opposite radial polarizations, as in the first sensor assembly I. Each outer core 189a, 189b is terminated at both ends by a pair of identical end caps 191, for example formed using silicon steel (or other material suitable for transformer cores). Each end cap 190 is semi-circular in shape with a semi-circular cutout, the diameter of which defines the largest dimension of the multi-conductor cable 6, 160 that can be received.

The two halves of the twenty-first sensor assembly XXI are placed together and secured together around the multi-conductor cable 6, 160. For example, the two halves may be hinged on one side and provided with a latch or similar securing mechanism on the other side.

When intended for use with non-armored multi-core cables, the magnets 190a, 190b may be omitted.

Referring additionally to fig. 31A and 31B, a twenty-second sensor assembly XXII is shown. The twenty-second sensor assembly XXII is identical to the fourth sensor assembly IV, except that a specific design of tangential sensor coils 41b to 48b is shown instead of the schematic cylindrical sensor coils 41 to 48 shown in fig. 4. Tangential sensor coils 41b to 48b are wound on the respective bobbins and supported within the channel defining structure 1. The tangential sensor coils 41b to 48b may be air coils, or magnetic materials may be inserted into the coils before or after winding. The particular shape shown for the tangential sensor coils 41b to 48b, being flat in the radial direction and extending along the longitudinal axis (rounded rectangle), may help to increase the total area of the sensor coils 41b to 48b without reducing the diameter of the cable 6 that can be accommodated (compared to a cylindrical sensor coil).

When intended for use with non-armored multi-core cables, the magnets 49a, 49b may be omitted.

Whether the channel is designed to encase a closed multi-conductor cable or remain open, the first through twenty-second sensor assemblies I,..xxii have been described as defining a circular channel (or portion thereof). However, the invention is not limited to sensor assemblies that are circular (or a portion thereof) in cross-section (perpendicular to the longitudinal axis of the housed multi-conductor cable).

For example, referring additionally to fig. 32A-32D, a twenty-third sensor assembly XXIII is shown. The twenty-third sensor assembly XXIII is similar to the twentieth sensor assembly XX except that lips 183 and 184 are omitted, tangential sensor coils 192 are used instead of solid state magnetic field sensors 182, and the first and second channel defining structures 180b and 181b are not semicircular. Instead, each channel-defining structure 180b and 181b defines a semi-oval (or "egg") shape in cross-section (or end view).

As another example, referring additionally to fig. 33A-33D, a twenty-fourth sensor assembly XXIV is shown. The twenty-fourth sensor assembly XXIV is identical to the twenty-third sensor assembly XXIII except that a solid state magnetic field sensor 182 is used in place of the tangential sensor coil 192. Or the twenty-fourth sensor assembly XXVI can be considered the same as the twentieth sensor assembly XX, except that lips 183 and 184 are omitted and that first and second semi-oval channel-defining structures 180b and 181b are used.

In a similar manner, any of the first to twenty-second sensor assemblies I, XXII may be modified to have a non-circular shape in cross-section (or end view).

Sensor assembly including current transformer

When measuring a multi-core cable (whether armored or unarmored), if there is a net current in the multi-core cable, it may result in saturation of any components of the channel defining structure including magnetically permeable material and/or saturation of the magnetic field sensor.

As described below, this problem can be alleviated (or even avoided) by mounting a sensor on the Current Transformer (CT) that has sufficient internal aperture to pass the multi-core cable (armored or unarmored) and has a rated current suitable for the intended network, or zero sequence current in the multi-core cable.

Referring additionally to fig. 34A-34E, a twenty-fifth sensor assembly XXV is shown. The twenty-fifth sensor assembly XXV is similar to the eighth sensor assembly VIII except that the twenty-fifth sensor assembly XXV does not have a separate ring 114 and channel-defining structure 113, but rather has a channel-defining structure 193 in the form of a unitary (SINGLE PIECE, one-piece) (or preferably two halves) magnetically permeable material that also provides a magnetic core for the windings of the current transformer coil 194. The current transformer coil 194 is provided in the form of eight sub-windings 194a to 194h which are connected together and placed in series with a load resistor 195.

The magnetic core 193 of the current transformer coil 194 includes a radially inwardly extending protrusion 196, the radial sensor coil 115 being wound around the protrusion 196, or the radial sensor coil 115 being received on the protrusion 196 (e.g., pre-wound on a plastic backbone). Preferably, the magnetic core 193 of the current transformer coil 194 is made of a material (e.g., silicon steel) suitable for a current transformer.

When it is desired to measure armored or unarmored multi-core cables, magnets 117a and 117b may be included, but if the twenty-fifth sensor assembly XXV is only intended for use with unarmored multi-core cables, magnets 117a, 117b may be omitted. When magnets 117a, 117b are included (as shown in fig. 34A-34E), the magnetic core 193 of the current transformer coil 194 may also include end or "lip" projections 197a, 197b at both ends along the longitudinal axis, which projections 197a, 197b coincide with magnets 117a and 117b. The end projections 197a, 197b help connect the return flux path between the magnets 117a and 117b.

The twenty-fifth sensor assembly XXV may be formed in two halves to provide a clip-on sensor, or may be pass-through (i.e., pass a multi-core cable through the current transformer coil 194).

The radial field entering the interior of the magnetic core 193 of the current transformer coil 194 is measured by the radial sensor coil 115. Solid state magnetic field sensors and/or tangential sensor coils may be used in addition to the radial sensor coils 115 or solid state magnetic field sensors and/or tangential sensor coils may be used instead of the radial sensor coils 115. The magnetic field sensor (whether radial/tangential sensor coils, solid state magnetic field sensors, or any other magnetic field sensor suitable for sensing dipole moments generated by unbalanced currents (symmetrical or anti-symmetrical currents) in the multi-core cable) may be placed between the core of the current transformer coil and the multi-core cable, or placed such that the core of the current transformer coil is located between the magnetic field sensor and the multi-core cable. Preferably, a magnetic field sensor (e.g., radial sensor coil 115 as shown or equivalent) is placed at least partially within the magnetic core 193 to obtain shielding from external magnetic fields, as explained below. However, whether the magnetic field sensor is disposed between the core of the current transformer coil and the multi-core cable or is disposed such that the core of the current transformer coil is between the magnetic field sensor and the multi-core cable, other effects such as preventing the core 193 of the current transformer coil from being saturated by net current in the multi-core cable may be obtained.

The current transformer coil 194 and the magnetic core 193 provide four functions:

1) The net current, common mode current or zero sequence current (in terms of voltage across the load resistor) in the cable is measured.

2) The magnetic core 193 of the current transformer partially shields the dipole sensing magnetic sensor (radial sensor coil 115 as shown) from magnetic fields caused by cable currents (or other magnetic field sources) that do not pass through the sensor. The degree of shielding is driven mainly by the aspect ratio of the core 193. Longer cores 193 (compared to their inner diameter) are expected to provide more effective shielding than shorter and larger inner diameter cores 193.

3) The magnetic core 193 of the current transformer increases the sensitivity of the dipole sensing magnetic sensor (radial sensor coil 115 as shown) by providing a low reluctance flux path around the outside of the dipole sensing magnetic circuit.

4) The core 193 is prevented from being saturated by net current in the multi-core cable.

Notably, it is preferable to use the current transformer coil 194 to perform functions 2) and 3) as compared to a tube of magnetically conductive material only (e.g., core 23 without secondary winding 194). This is because the windings of the current transformer coil 194, in combination with their approximate short circuit provided by the load resistor 195, provide a balanced current for the net current in the multi-core cable. This prevents the core 193 from being saturated with net current in the multi-core cable (function 4)). Otherwise, this can easily occur with a high permeability core 193-because the high permeability core is necessary to provide optimal shielding from external magnetic fields-causing the core 193 to heat up, a voltage step is imposed on the multi-core cable net current when the core 193 is saturated, modulating the sensitivity of the dipole sensing magnetic sensor (radial sensor coil 115 as shown), and also introducing interference into the dipole sensing magnetic sensor (radial sensor coil 115 as shown) from different portions of the core 193 that are saturated at different times.

The level of shielding provided by the long magnetic core 193 is approximately the magnetic permeability of the magnetic core 193 times the thickness/diameter of the magnetic core 193. For example, for a magnetic core 193 of thickness 10 mm, outer diameter 100mm (thus inner diameter 80 mm) and relative permeability 10,000, this can provide a 1000-fold (shielding level) improvement. Such a large core 193 would saturate (2 tesla) with a net current of 50A passing through the sensor. For a shorter high permeability core 193, the shielding improvement will be limited by geometry (length/inner diameter).

Although the twenty-fifth sensor assembly XXV is shown using radial sense coils 115, these radial sense coils 115 may be replaced with any other magnetic field sensor suitable for detecting dipole components (e.g., tangential sense coils and/or solid state magnetic field sensors described herein, or a combination thereof).

The magnets 117a, 117b may be omitted when no measurement of the armored multi-core cable 6 is required. When the magnets 117a, 117b are omitted, the protrusions 197a, 197b may be omitted, or the protrusions 197a, 197b may be left to help define an aperture/channel for receiving a multi-conductor cable.

Any optional features, modifications and/or applications of the first to twenty-fourth sensor assemblies XXIV are equally applicable to the twenty-fifth sensor assembly XXV unless clearly incompatible.

Any of the foregoing first to twenty-fourth sensor assemblies I to XXIV may be modified to include current transformer coils 24 by, for example, replacing the corresponding channel-defining structures with suitably shaped magnetic cores and then adding current transformer coil 24 windings. As explained, the degree of shielding obtained will depend on the aspect ratio (length to diameter ratio) and can be improved by changing the aspect ratio. When modified in this manner to include the current transformer coil 24, any of the first to twenty-fourth sensor assemblies XXIV may omit any magnet included if the armored multi-core cable does not need to be measured. Such a modified first sensor assembly I to twenty-fourth sensor assembly XXIV would still obtain more or less of the advantages/functions 1), 2) and 3) described in relation to the twenty-fifth sensor assembly XXV).

Referring additionally to fig. 35A and 35B, a twenty-sixth sensor assembly XXVI is shown. The twenty-sixth sensor assembly XXVI is identical to the twenty-fifth sensor assembly XXV except that the magnetic core 23 does not include the protrusion 196 such that the radial sensor coil 115 is an air core coil.

If the end projections 197a, 197b are also omitted, the twenty-sixth sensor assembly XXVI can be produced in a particularly simple manner, as also shown with reference to fig. 36A to 36C.

Fig. 35A shows a skeletal assembly 198 for forming the sensor coil 115 and the current transformer coil 194 of the twenty-sixth sensor assembly XXVI. The carcass assembly 198 includes a first tangential carcass 199 with a staggered arrangement of second radial carcass 200. The radial skeleton 200 extends perpendicular to the support plate 201 (and is integrally formed with the support plate 201). The tangential skeleton 199 and the support plate 201 are connected by a thin flexible hinge portion 202. Each tangential skeleton 199 includes a respective rectangular through-hole 203, and each radial skeleton 200 includes a respective rectangular through-hole 204.

The radial sensor coil 115 is fabricated on a radial backbone 200, the backbone 200 having pairs of first and second backbone assemblies 198 (shown in fig. 36A) in a flattened state. Four sub-windings 194a to 194d of the current transformer coil 194 are fabricated on the tangential bobbin 199 of the first bobbin assembly 198, while the remaining sub-windings 194e to 194h are fabricated on the tangential bobbin 199 of the second bobbin assembly 198.

In particular, referring to fig. 36B, each of the first and second carcass assemblies 198 is bent by bending the flexible hinge section 202, as shown, and the semi-cylindrical core section 205 passes through the through-hole 203 of the tangential carcass 199. Once the two halves are completed, magnets 117a, 117b and any end caps (not shown) may be added as needed, and the two halves assembled to complete the twenty-sixth sensor assembly XXVI (e.g., the two halves may be hinged on one side and fixable by a latch or similar mechanism on the other side).

If it is desired that the sensing coil 115 has a magnetically permeable core, a magnetically permeable material formed into a correct shape may be inserted into the through hole 204 of the radial backbone either before or after winding the radial sensor coil 115.

The skeletal assembly 198 may be modified to accommodate solid state magnetic field sensors that may be mounted to the support plate 201 directly or via a flexible circuit board/PCB prior to folding the skeletal assembly 198 and inserting the semi-cylindrical core section 205. Similarly, the orientation of the second armature 200 may be changed from radial to tangential (or may alternate) to allow for the formation of other magnetic field sensor configurations.

Referring additionally to fig. 37A and 37B, a twenty-seventh sensor assembly XXVII is shown. The twenty-seventh sensor assembly XXVII comprises a toroidal transformer core 206 with a continuous spiral transformer coil 207 wound thereon. The ends 208 of the transformer coil are connected via load resistors (not shown in fig. 36A and 36B) to form a current transformer. Twelve (a variable number of) solid state magnetic field sensors 209 are supported on a substrate 210 (e.g., a flexible circuit board/PCB), the substrate 210 being disposed just inside the inner diameter of the transformer coil 207.

The twenty-seventh sensor assembly XXVII functions in the same manner as already described in relation to the twenty-fifth sensor assembly XXV and/or the twenty-sixth sensor assembly XXVI, although the twenty-seventh sensor assembly XXVII has a relatively reduced shielding due to its shorter length parallel to the longitudinal direction in which the multi-conductor cable is housed.

For use with armored multi-conductor cables, a magnet may be added to the twenty-seventh sensor assembly XXVII.

Referring additionally to fig. 38A and 38B, a twenty-eighth sensor assembly XXVIII is shown. The twenty-eighth sensor assembly XXVIII is identical to the twenty-seventh sensor assembly XXVII, except that the substrate 210 is supported on the inner diameter of the toroidal core 206 and the solid state magnetic field sensor 209 is contained within the coil of the continuous spiral transformer coil 207.

For use with armored multi-conductor cables, a magnet may be added to the twenty-eighth sensor assembly XXVIII.

The cross-sectional/end view shape of the sensor assembly including the current transformer is also not limited to a circular shape. For example, referring additionally to fig. 39A-39D, a twenty-ninth sensor assembly XXIX is shown.

The twenty-ninth sensor assembly XXIX is similar to the twenty-fourth sensor assembly XXIV, but with the addition of a transformer coil sub-winding 211 surrounding the first and second channel defining structures 180b, 181b, which first and second channel defining structures 180b, 181b are also formed of magnetically permeable material and form the core of a transformer coil formed by connecting the transformer coil sub-windings 211 together. The transformer coil sub-windings 211 are also connected in series with a load resistor (not shown) to form a current transformer. The first and second channel defining structures 180b and 181b are hinged at one side to allow the multi-core cable to be accommodated through the transformer coil formed by connecting the sub-windings 211. The other side can then be closed and preferably secured by means of, for example, a latch or similar mechanism. Alternatively, a spring or similar biasing means may be included to urge the non-hinged ends of the first and second channel defining structures 180b, 181b together.

For use with armored multi-conductor cables, a magnet may be added to the twenty-ninth sensor assembly XXIX.

Referring additionally to fig. 40A and 40B, a thirty-first sensor assembly XXX is shown. The thirty-second sensor assembly XXX includes a rogowski coil 212 and a plurality of magnetic field sensors 213. For illustrative purposes, in fig. 40A and 40B, the magnetic field sensor 213 is shown as a hollow radial sensor coil, but types of magnetic sensors of the type described herein may be used, including but not limited to solid state magnetic field sensors, radial sensor coils (hollow or magnetically permeable material cores), tangential sensor coils (hollow or magnetically permeable material cores), and the like.

The rogowski coil 212 and the plurality of magnetic field sensors 213 are supported by a channel defining structure, which is not shown in fig. 40A and 40B, but may be configured as described with respect to the foregoing sensor assembly.

The thirty-second sensor assembly XXX is configured such that when the device is coupled to the multi-core cable 214 (e.g., a three-core cable as shown), an area of the multi-core cable 214 passes through the rogowski coil 212. At least one of the magnetic field sensors 213 is disposed near the rogowski coil and oriented to detect a magnetic field component originating from the region of the multi-core cable 214. Preferably, the magnetic field sensor 213 surrounds the multi-core cable 214 to allow sensing of dipole fields and measurement of the derived quantities, as described above with respect to the first sensor assembly I to the twenty-ninth sensor assembly XXIX. Rogowski coil 212 is used to measure the net current.

Or in some examples rogowski coil 212 may be flexible (to allow winding on a region of multi-core cable 214). In this case, the rogowski coil 212 and the magnetic field sensor 213 may be supported by a flexible or hinged structure.

Positioning the rogowski coil 212 and the magnetic field sensor 213 in close proximity to each other allows direct comparison of the measurements. For example, the net current measurements from rogowski coil 212 may be used to examine individual core currents inferred using magnetic field sensor 213.

The precise position of the magnetic field sensor 213 with respect to the rogowski coil 212 is not limited to the case shown in fig. 40A and 40B (i.e., the magnetic field sensor 213 is disposed adjacent to the rogowski coil 212 along the axial direction of the multi-core cable 214 (when in use)). For example, at least one of the one or more magnetic field sensors 213 may be disposed inside the rogowski coil 212, or at least partially inside the rogowski coil 212. In other words, in use, between rogowski coil 212 and multicore cable 214. Or at least one of the one or more magnetic field sensors may be disposed outside of rogowski coil 212. In other words, spaced apart from multicore cable 214 by rogowski coil 212.

Although the multi-conductor cable 214 is shown as non-armored, a magnet may be added to the thirty-sensor assembly XXX for use with armored multi-conductor cables.

Modification of

It will be appreciated that various modifications may be made to the embodiments described above. Such modifications may involve equivalent and other features and/or methods which are already known in the design, manufacture and use of electrical test and measurement equipment and component parts thereof and which may be used instead of or in addition to features already described herein. Features of one embodiment may be substituted or supplemented by features of another embodiment.

Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same application as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present application. The applicant hereby gives notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

1. An apparatus for coupling to a multi-core wire-armored cable, comprising:

One or more magnets, and

One or more magnetic field sensors;

wherein the apparatus is configured such that when the apparatus is coupled to the multi-core wire armored cable:

A magnetic field corresponding to the one or more magnets is applied to a region of the multi-core wire-armored cable, and

Each magnetic field sensor is oriented to detect a magnetic field component originating from a region of the multi-core wire-armoured cable.

2. The apparatus of claim 1, wherein at least one of the one or more magnets comprises a permanent magnet.

3. The apparatus of claim 1 or 2, wherein at least one of the one or more magnets comprises an electromagnet.

4. A device according to any one of claims 1 to 3, wherein at least one of the one or more magnetic field sensors comprises a coil.

5. The apparatus of any of claims 1-4, wherein at least one of the one or more magnetic field sensors comprises a solid state magnetic field sensor device.

6. The apparatus of any one of claims 1 to 5, wherein the magnetic field corresponding to the one or more magnets has an amplitude of at least 5mT within the region.

7. The apparatus of any one of claims 1 to 6, the apparatus configured such that a magnetic field corresponding to the one or more magnets is time-varying.

8. The apparatus of any one of claims 1 to 6, the apparatus configured such that a magnetic field corresponding to the one or more magnets is constant.

9. The apparatus of any of claims 1-8, wherein the apparatus is configured to mechanically couple to the multi-core wire-armoured cable using a magnetic force generated by applying the magnetic field to a wire-armour layer.

10. The apparatus of any of claims 1 to 9, comprising structure supporting the one or more magnets and the one or more magnetic field sensors.

11. The apparatus of claim 10, wherein the structure comprises a channel configured to receive the multi-core wire-armored cable.

12. The device of claim 11, wherein the cross-section of the channel has a circular or circular arc shape.

13. The device of claim 12, wherein the cross-section of the channel has a shape that is non-circular and does not correspond to an arc of a circle.

14. The device of any one of claims 11 to 13, wherein the channel is open.

15. The apparatus of any of claims 11-13, wherein the channel is defined by first and second components of the structure configured to encase the multi-core wire-armored cable when the multi-core wire-armored cable is received within the channel.

16. The apparatus of any of claims 11-13, wherein the structure comprises two or more components configured to encase or wrap the multi-core wire-armored cable to define the channel.

17. The apparatus of any one of claims 1 to 16, further comprising a net current sensor configured to measure a net current through the multi-core wire-armoured cable when the apparatus is coupled to the multi-core wire-armoured cable.

18. The apparatus of any one of claims 1 to 17, wherein at least one of the one or more magnetic field sensors comprises a coil, wherein each coil is wound on a sense pole piece.

19. The apparatus of any one of claims 1 to 18, wherein at least one of the one or more magnets comprises an electromagnet, wherein each electromagnet is wound on a pole piece.

20. The apparatus of any one of claims 1 to 19, comprising two or more magnetic field sensors.

21. The apparatus of any one of claims 1 to 20, wherein the one or more magnetic field sensors comprise a first set of first magnetic field sensors and a second set of second magnetic field sensors;

wherein the first set of first magnetic field sensors and the second set of second magnetic field sensors are arranged to be spaced apart along an axial direction of the multi-core wire-armored cable when the multi-core wire-armored cable is coupled to the device.

22. A sensor, comprising:

The apparatus of any one of claims 1 to 21;

And a controller connected to the one or more magnetic field sensors and configured to calculate one or more derived quantities for part or all of the core of the multi-core wire-armoured cable based on magnetic field components measured by the magnetic field sensors.

23. A sensor, comprising:

The apparatus of any one of claims 1 to 21, further configured to generate one or more signals based on the output of the one or more magnetic field sensors, each signal being proportional to a differential current between cores of the multi-core wire-armoured cable when the multi-core wire-armoured cable is coupled to the apparatus;

A link corresponding to each signal for connection to a control and/or measurement system.

24. The sensor of claim 22 or 23, further comprising one or more voltage sensors, wherein the one or more derived quantities comprise one or more power values.

25. A system comprising a sensor according to any one of claims 22 to 24 coupled to provide input to a measurement device.

26. The system of claim 25, wherein the measurement device is a power quality analyzer.

27. The system of claim 25, wherein the measurement device is a power quality recording apparatus.

28. A method, comprising:

coupling the apparatus of any one of claims 1 to 21 to the multi-core wire-armoured cable, or coupling the apparatus of the sensor of claims 22 to 24 or the system of claims 25 to 27 to the multi-core wire-armoured cable such that a magnetic field corresponding to the one or more magnets is applied to an area of the multi-core wire-armoured cable;

The one or more magnetic field sensors are used to measure a magnetic field component originating from a region of the multi-core wire-armoured cable.

29. The method of claim 28, wherein a magnetic field corresponding to the one or more magnets saturates the wire armor in the region.

30. The method of claim 28 or 29, further comprising calculating one or more derived quantities for part or all of the core of the multi-core wire-armoured cable based on magnetic field components measured by the magnetic field sensor.

31. An apparatus for coupling to a multi-core cable, comprising:

a first set of one or more first magnetic field sensors;

a second set of one or more second magnetic field sensors;

Wherein the apparatus is configured such that when the apparatus is coupled to a multi-core cable:

Each first magnetic field sensor is oriented to detect a magnetic field component originating from a first region of the multi-core cable;

each second magnetic field sensor is oriented to detect a magnetic field component originating from a second region of the multi-core cable;

Wherein the first region is spaced apart from the second region along a length of the multi-core cable.

32. The apparatus of claim 31, further comprising one or more magnets arranged such that when the apparatus is coupled to the multi-core cable, a magnetic field corresponding to the one or more magnets is applied to a first region and the second region of the multi-core cable.

33. An apparatus for coupling to a multi-core cable, comprising:

a current transformer coil;

One or more magnetic field sensors;

wherein the apparatus is configured such that when the apparatus is coupled to the multi-core cable:

the area of the multi-core cable passes through the current transformer coil;

The one or more magnetic field sensors are disposed at least partially between the core of the current transformer coil and the multi-core cable, and wherein at least one of the magnetic field sensors is oriented to detect a magnetic field component originating from a region of the multi-core cable.

34. The apparatus of claim 33 or 34, wherein the magnetic core of the current transformer coil comprises magnetically permeable material.

35. The apparatus of claim 33 or 34, wherein the current transformer coil comprises two or more sub-coils.

36. The apparatus of any of claims 33 to 35, wherein the apparatus is configured such that a region of the multi-core cable received by the current transformer coil is oriented in an axial direction;

wherein the current transformer coils extend along the axial direction on both sides of the one or more magnetic field sensors.

37. The apparatus of claim 36, wherein the current transformer coil extends in the axial direction for a length greater than or equal to half an inner diameter of the current transformer coil.

38. The apparatus of any one of claims 33 to 37, wherein at least one of the one or more magnetic field sensors comprises a sensor coil.

39. The apparatus of any of claims 33 to 38, wherein at least one of the one or more magnetic field sensors comprises a solid state magnetic field sensor device.

40. The apparatus of any of claims 33 to 39, comprising structure supporting the current transformer coil and the one or more magnetic field sensors.

41. The apparatus of claim 40, wherein the structure comprises a channel configured to receive the multi-core cable.

42. The device of claim 41, wherein the cross-section of the channel has a circular or arcuate shape.

43. The device of claim 41, wherein the cross-section of the channel has a shape that is non-circular and does not correspond to an arc of a circle.

44. The device of any one of claims 41 to 43, wherein the channel is open.

45. The apparatus of any of claims 41-44, wherein the channel is defined by first and second components of the structure configured to encase the multi-conductor cable when the multi-conductor cable is received within the channel.

46. The apparatus of any of claims 41-44, wherein the structure comprises two or more components configured to encase or wrap the multi-core cable to define the channel.

47. The apparatus of any one of claims 33 to 46, comprising two or more magnetic field sensors.

48. The apparatus of any one of claims 33 to 47, further comprising one or more magnets;

Wherein the apparatus is configured such that when the apparatus is coupled to the multi-core cable, a magnetic field corresponding to the one or more magnets is applied to a region of the multi-core cable passing through the current transformer coil.

49. The apparatus of any one of claims 33 to 48, wherein the one or more magnetic field sensors comprise a first set of first magnetic field sensors and a second set of second magnetic field sensors;

wherein the first set of first magnetic field sensors and the second set of second magnetic field sensors are arranged to be spaced apart along an axial direction of the multi-core cable when the multi-core cable is coupled to the device.

50. A sensor, comprising:

the apparatus of any one of claims 33 to 49;

A controller connected to the one or more magnetic field sensors and configured to:

one or more derived quantities are calculated for some or all of the cores of the multi-core cable based on the magnetic field components measured by the magnetic field sensor.

51. The sensor of claim 50, wherein the controller is further configured to calculate a net current through the multi-core cable based on measurements using the current transformer coil.

52. A sensor, comprising:

the apparatus of any one of claims 33 to 49, further configured to generate one or more signals based on an output of the one or more magnetic field sensors, each signal being proportional to a differential current between cores of the multi-core cable when the multi-core cable is coupled to the apparatus;

53. The sensor of claim 52, wherein the apparatus is further configured to generate a net current signal based on an output from the current transformer coil.

54. The sensor of any one of claims 50 to 53 further comprising one or more voltage sensors, wherein the one or more derived quantities comprise one or more power values.

55. The sensor of claim 54, the sensor configured to use the one or more voltage sensors to correctly assign phases to cores of the multi-core cable.

56. A system comprising a sensor according to any one of claims 50 to 55 coupled to provide input to a measurement device.

57. A method, comprising:

Coupling the apparatus of any one of claims 33 to 49 to a multi-core cable, or coupling the apparatus of the sensor of claims 50 to 55 or the system of claim 56 to the multi-core cable such that a region of the multi-core cable passes through the current transformer coil;

the one or more magnetic field sensors are used to measure a magnetic field component originating from a region of the multi-core cable.

58. The method of claim 57, further comprising measuring a net current through the multi-core cable using the current transformer coil.

59. An apparatus for coupling to a multi-core cable, comprising:

A rogowski coil;

One or more magnetic field sensors;

The region of the multi-core cable passes through the rogowski coil or the rogowski coil is wound on the region of the multi-core cable;

at least one of the magnetic field sensors is disposed adjacent to the rogowski coil and oriented to detect a magnetic field component originating from a region of the multi-core cable.