CN115825519A - Measurement system of cantilever beam type extrinsic optical fiber double-Fabry-Perot current transformer - Google Patents

Abstract

The invention provides a measuring system of a cantilever beam type extrinsic optical fiber double Fabry-Perot current transformer, and belongs to the technical field of measuring devices. The invention comprises the following steps: the system comprises a magnetic conduction loop, a cantilever beam type extrinsic Fabry-Perot sensor, a permanent magnet and a demodulation system; the cantilever beam type extrinsic Fabry-Perot sensor is provided with two Fabry-Perot cavities, wherein one Fabry-Perot cavity is influenced by the strain of a cantilever beam and the ambient temperature, and the other Fabry-Perot cavity is only influenced by the ambient temperature. According to the invention, two Fabry-Perot cavities are arranged, wherein one Fabry-Perot cavity is influenced by the strain of the cantilever beam and the ambient temperature, and the other Fabry-Perot cavity is only influenced by the ambient temperature, so that the influence of the ambient temperature on the sensor can be eliminated by differentiating the output optical signals of the two Fabry-Perot cavities, and the current measurement range and sensitivity are improved.

Description

A Measuring System of Cantilever Beam Extrinsic Fiber-optic Double Fappaure Current Transformer

technical field

The invention relates to the technical field of current measurement devices, in particular to a measurement system for a cantilever beam type extrinsic fiber optic double Fappaure current transformer.

Background technique

With the continuous advancement of science and technology and the continuous increase of electricity consumption, the power transmission industry is becoming more and more sophisticated and gradually developing towards intelligence and networking. Therefore, the requirements for power transmission are becoming more and more safe and reliable. This requires that the development of the relay protection system should follow the footsteps of the power industry. The core part of the relay protection in the power system is the current measurement. The current measurement will directly affect the reliability of the system analysis and the accuracy of the system detection. , The safety of electric energy measurement, these are the key factors to maintain the normal operation of the power system, so the accuracy and reliability requirements for current measurement and fault monitoring equipment are getting higher and higher. With the increase of power system transmission capacity and the improvement of voltage level, traditional electromagnetic current transformers can no longer meet the needs of smart grids due to the shortcomings of magnetic saturation, narrow measurement frequency band, insulation safety hazards, and large volume.

With the development of optical fiber sensing technology, optical current transformers have been widely used in many fields due to their advantages of anti-electromagnetic interference, wide measurement frequency range, small size, and online monitoring. However, since the optical sensor is greatly affected by the ambient temperature, temperature compensation measures must be considered.

Therefore, there is an urgent need for a measuring device that can solve the technical problem of temperature and strain cross-sensitivity and improve the range and sensitivity of the measured current.

Contents of the invention

In view of this, in order to solve the technical problem of temperature and strain cross-sensitivity, and improve the range and sensitivity of the measurement current, the present invention provides a measurement system for a cantilever beam type extrinsic fiber optic double F-Pe current transformer, which is configured by setting two methods Pert cavity, one of which is affected by the strain of the cantilever beam and the ambient temperature, and the other Fap cavity is only affected by the ambient temperature. By making a difference between the output optical signals of the two Fap cavity, the influence of the ambient temperature on the sensor can be eliminated. The effect of improving the range and sensitivity of current measurement.

To achieve the above object, the present invention provides the following technical solutions:

A measurement system for a cantilever beam type extrinsic fiber optic double Fappau current transformer, comprising:

A magnetic conduction circuit, on which an induction coil is wound;

A cantilever beam extrinsic Fappel sensor, which has two Fappel cavities, one of which is affected by the strain of the cantilever beam and the ambient temperature, and the other is only affected by the ambient temperature;

A permanent magnet, which is arranged on the cantilever beam type extrinsic Fapp sensor, is used to drive the cantilever beam to generate periodic strain;

The demodulation system is used to restore the signal of the current to be measured, which includes:

Laser, the optical signal sent by the coupler enters two Fab cavities for refraction and reflection, and finally forms a stable interference phenomenon at both ends of the Fap cavity;

An interferometer, which is used to receive the interference signal generated by two Fab cavities, and make the interference signal into a periodic signal through the phase modulator in it;

an optical-to-electrical converter for demodulating the periodic signal into an electrical signal;

The data acquisition card is used for collecting and demodulating the electrical signal.

Preferably, the cantilever beam type extrinsic Fab sensor includes:

Cantilever beam quartz diaphragm, one end of which is suspended and the other end is fixed;

An optical fiber, a pigtail coated with a reflective film on its end face and the cantilever beam quartz diaphragm form two Fab cavities respectively.

Preferably, the cantilever beam type extrinsic Fappau sensor also includes a glass sleeve and a fixed structure;

The two glass sleeves are connected through the fixing structure, the other end of the cantilever quartz diaphragm is fixed on the fixing structure, and the optical fibers respectively pass through the two glass sleeves.

Preferably, the laser is a DFB semiconductor laser.

Preferably, the coupler is a 3db coupler.

Preferably, the interferometer is a Mach-Zehnder interferometer.

Compared with the prior art, the present invention has the following beneficial effects:

The measurement system of the cantilever beam type extrinsic fiber optic F-P current transformer provided by the present invention is provided with two F-P cavity, one of which is affected by the strain of the cantilever beam and the ambient temperature, and the other F-P cavity is only affected by the environment For the influence of temperature, the influence of ambient temperature on the sensor can be eliminated by making a difference between the output optical signals of the two Fabry cavities, and the range and sensitivity of current measurement can be improved.

The measurement system of the cantilever beam type extrinsic fiber-optic F-P current transformer provided by the invention adopts the demodulation method of the Mach-Zehnder interferometer, has high detection precision for dynamic strain signals, and is suitable for the measurement of alternating current.

Description of drawings

Figure 1 is a schematic diagram of the relationship between the reflected light power of the extrinsic optical fiber F-P sensor and the cavity length;

Fig. 2 is the structural schematic diagram of the cantilever beam type extrinsic optical fiber Fab sensor;

Fig. 3 is the schematic diagram of the current measuring system of optical fiber current transformer;

In the figure, 1. Magnetic circuit, 11. Induction coil, 2. Cantilever beam extrinsic F-P sensor, 21. F-P cavity, 22. Cantilever quartz diaphragm, 23. Optical fiber, 24. Glass sleeve, 25 .fixed structure, 3. permanent magnet, 4. demodulation system, 41. laser, 42. coupler, 43. phase modulator, 44. photoelectric converter, 45. data acquisition card.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only part of the embodiments of the present invention, not all embodiments, based on The embodiments of the present invention and all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "top/bottom" etc. are based on the orientations shown in the drawings Or positional relationship is only for the convenience of describing the present invention and simplifying the description, but does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that, unless otherwise specified and limited, the terms "installed", "set with", "sleeved/connected", "connected", etc. should be understood in a broad sense, such as " Connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be an internal connection between two components. connectivity. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

As shown in Fig. 3, the present invention provides a kind of measuring system of cantilever beam type extrinsic fiber-optic F-Per current transformer, comprising:

A magnetic conduction circuit 1, on which an induction coil 11 is wound;

The cantilever beam type extrinsic Faptor sensor 2 has two Fapton cavities 21, one of which is affected by the strain of the cantilever beam and the ambient temperature, and the other is only affected by the ambient temperature;

A permanent magnet 3, which is arranged on the cantilever beam type extrinsic Fapp sensor 2, is used to drive the cantilever beam to generate periodic strain;

The demodulation system 4 is used to restore the signal of the current to be measured, which includes:

The laser 41 sends an optical signal through the coupler 42 into the two Fab cavities 21 for refraction and reflection, and finally forms a stable interference phenomenon on both ends of the Fab cavities 21;

An interferometer, which is used to receive the interference signals produced by the two Fab cavities, and make the interference signals into periodic signals through the phase modulator 43 therein;

a photoelectric converter 44 for demodulating the periodic signal into an electrical signal;

The data acquisition card 45 is used for collecting and demodulating the electrical signals.

In the present invention, the cantilever beam type extrinsic Fappau sensor 2 includes:

Cantilever beam quartz diaphragm 22, one end of which is suspended and the other end is fixed;

An optical fiber 23 , a tail fiber coated with a reflective film on its end face and the cantilever beam quartz diaphragm 22 respectively form two Fab cavities 21 .

In the present invention, the cantilever beam type extrinsic Fappau sensor 2 also includes a glass sleeve 24 and a fixed structure 25;

The two glass sleeves 24 are connected by the fixing structure 25, the other end of the cantilever beam quartz diaphragm 22 is fixed on the fixing structure 25, and the optical fibers 23 respectively pass through the two glass sleeves twenty four.

In the present invention, the laser 41 is a DFB semiconductor laser.

In the present invention, the coupler 42 is a 3db coupler.

In the present invention, the interferometer is a Mach-Zehnder interferometer, which has high detection accuracy for dynamic strain signals and is suitable for measuring alternating current.

In the measurement system of the above-mentioned cantilever beam type extrinsic fiber optic F-Per current transformer provided by the present invention, the cantilever beam type extrinsic F-P sensor 2 is composed of two parallel planes with a certain reflectivity to form a F-P cavity 21, which has a simple structure and high sensitivity. High, fast response advantages. Wherein, the Fab cavity 21 is composed of a cantilever beam quartz diaphragm and a pigtail end face of an optical fiber coated with a reflective film, and the cavity is air. According to the basic principle of multi-beam interference, the output optical power of the cantilever beam extrinsic F-P sensor 2 reflection spectrum is:

In the formula, I ₀ (λ) is the intensity of the incident light, R ₁ and R ₂ are the reflectivity of the pigtail end face and the quartz diaphragm respectively, l is the length of the F-P cavity, λ is the wavelength of the incident light, and n is the medium in the cavity Refractive index, n=1 when the medium is air. As shown in FIG. 1 , it is a schematic diagram of the relationship between the reflected optical power of the cantilever beam extrinsic F-P sensor 2 and the cavity length.

As shown in Figure 2, the present invention will suspend one end of the cantilever arm quartz diaphragm 22 (forming a floating end), and the other end is fixed on the fixed structure 25 (forming a fixed end) to form a cantilever beam structure, and then two end surfaces are plated The pigtail of the optical fiber with reflective film and the cantilever quartz diaphragm 22 constitute two Fab cavities 21. Preferably, the distance between the pigtail end face of the optical fiber and the cantilever quartz diaphragm 22 is adjusted by using an optical three-axis micro-motion instrument. Make the cavity lengths of the two Fabber cavities 21 consistent, and then use ultraviolet curing glue to fix the optical fiber pigtails. This kind of structure can make one of the floating end of the Fabry cavity be affected by the cantilever beam strain and the ambient temperature, while the other fixed end Fapocket cavity is only affected by the ambient temperature. The influence of ambient temperature on the sensor can be eliminated.

In the present invention, when calculating the natural frequency of the cantilever quartz diaphragm 22, Euler-Bernoulli theory or Timoshenko beam theory can be used to list the motion differential equation and boundary conditions of the cantilever quartz diaphragm 22, Solve the equation to get the first few natural frequencies. When the frequency of the measured signal does not exceed the first-order natural frequency, the amplitude of the cantilever quartz diaphragm 22 is relatively stable and reaches the maximum at the natural frequency. The first-order natural frequency of the cantilever quartz diaphragm 22 is:

In the formula, h and L are the thickness and length of the cantilever quartz diaphragm 22 respectively, and ρ and E are the mass density and Young's modulus of the cantilever quartz diaphragm 22 respectively. It can be seen that the shorter the length and the greater the thickness of the cantilever quartz diaphragm 22, the higher its first-order natural frequency.

In the present invention, the demodulation system is composed of a laser, a coupler, a phase modulator, a photoelectric converter and a data acquisition card, wherein the laser 41 is preferably a DFB semiconductor laser, and its central operating wavelength is a narrow linewidth distributed feedback laser of 1550nm . The optical signal sent by the DFB semiconductor laser enters the two Fabry cavities through the coupler 42, undergoes multiple refraction and reflection between the end face of the fiber pigtail and the diaphragm, and finally forms a stable interference phenomenon at both ends of the Fabry cavity, and then the two The reflected light enters the interferometer. Wherein, the coupler 42 is preferably a 3dB coupler, and the interferometer is preferably a Mach-Zehnder interferometer.

The Mach-Zehnder interferometer is composed of a coupler and a phase modulator. It receives two reflected lights, one as a measuring arm and the other as a reference arm. The phase modulator 43 winds and pastes the optical fiber on the annular piezoelectric ceramic, and then stimulates the piezoelectric ceramic to make the optical fiber vibrate periodically, so that the interference signal becomes a periodic signal. The Mach-Zehnder interferometer converts the change of the reflected light caused by the change of the cavity length of the Fab cavity 21 into the change of the phase of the interference signal, and finally realizes the demodulation of the output optical signal through the photoelectric converter 44, and the output terminal of the photoelectric converter 44 It is connected with the data acquisition card 45, and the electrical signal demodulated by the photoelectric converter 44 is collected by the data acquisition card 45.

As shown in Figure 3, it shows a preferred embodiment of the measurement system of a cantilever beam type extrinsic fiber-optic F-Per current transformer provided by the present invention, which consists of a magnetic circuit 1, an induction coil 11, a permanent magnet 3 and a cantilever beam type non-intrinsic Intrinsic fiber-optic F-P sensor 2 is realized. Among them, the magnetic conduction circuit 1 is set on the tested circuit. When there is current flowing in the tested circuit, due to electromagnetic induction, the induction coil 11 wound on the magnetic conduction circuit 1 will generate an alternating induced electromotive force, which will affect the fixed pole. The permanent magnet 3 generates periodic attractive and repulsive forces, and the permanent magnet 3 is fixed with one end of the cantilever quartz diaphragm 22 to drive the suspended end of the cantilever quartz diaphragm 22 to generate periodic strain. Under the effect of stress, the cavity length of the Fab cavity 21 on the cantilever beam type extrinsic fiber Fap sensor 2 changes, and then the amplitude and phase of the sensor output light will change, and finally restore the measured current through the demodulation system The signal is presented to an oscilloscope.

The present invention shows the preferred connection mode of demodulation system in Fig. 3, and laser 41 is connected with optical fiber 23 by coupler 42, and the optical signal that makes it send enters two Fab cavities through coupler, carries out refraction and reflection, finally A stable interference phenomenon is formed on both ends of the Fab cavity; the interference signal is transmitted to the phase modulator 43 in the interferometer through the coupler 42, so that the interference signal becomes a periodic signal, and finally converted into an electrical signal by the photoelectric converter 44. The signal is collected by the data acquisition card 45 and presented on the oscilloscope.

The above are only preferred specific embodiments of the present invention; however, the protection scope of the present invention is not limited thereto. Anyone familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention and its improved concept to make equivalent replacements or changes shall fall within the scope of protection of the present invention.

Claims (6)

1. A measurement system of a cantilever beam type extrinsic optical fiber double Fabry-Perot current transformer is characterized by comprising:

a magnetic conductive loop, on which an induction coil is wound;

the cantilever beam type extrinsic Fabry-Perot sensor is provided with two Fabry-Perot cavities, wherein one Fabry-Perot cavity is influenced by the strain of a cantilever beam and the ambient temperature, and the other Fabry-Perot cavity is only influenced by the ambient temperature;

the permanent magnet is arranged on the cantilever beam type extrinsic Fabry-Perot sensor and is used for driving the cantilever beam to generate periodic strain;

demodulation system, is used for reducing the signal of the electric current that awaits measuring, it includes:

the laser device, the optical signal that it sends enters two Fabry-Perot cavities through the coupler, refract and reflect, form the stable interference phenomenon in two terminal surfaces of Fabry-Perot cavity finally;

the interferometer is used for receiving interference signals generated by the two Fabry-Perot cavities and converting the interference signals into periodic signals through the phase modulators in the interferometer;

a photoelectric converter for demodulating the periodic signal into an electric signal;

and the data acquisition card is used for acquiring the demodulated electric signals.

2. The measurement system of an cantilevered extrinsic fiber dual-Fabry-Perot current transformer according to claim 1, wherein said cantilevered extrinsic Fabry-Perot sensor comprises:

one end of the cantilever beam quartz membrane is suspended in the air, and the other end is fixed;

and the tail fiber of which the end surface is plated with a reflecting film and the cantilever beam quartz diaphragm respectively form two Fabry-Perot cavities.

3. The measurement system of an cantilever extrinsic fiber double Fabry-Perot current transformer according to claim 2, wherein said cantilever extrinsic Fabry-Perot sensor further comprises a glass sleeve and a fixed structure;

the two glass sleeves are connected through the fixing structure, the other end of the cantilever beam quartz diaphragm is fixed on the fixing structure, and the optical fibers penetrate through the two glass sleeves respectively.

4. The measurement system of an cantilever beam type extrinsic fiber double Fabry-Perot current transformer according to claim 1, wherein the laser is a DFB semiconductor laser.

5. The measurement system of an cantilevered beam extrinsic fiber double Fabry-Perot current transformer according to claim 1, wherein said coupler is a 3db coupler.

6. The measurement system of an cantilever beam type extrinsic optical fiber double Fabry-Perot current transformer according to claim 1, wherein the interferometer is a Mach-Zehnder interferometer.

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