CN113608150B - Single-phase transformer system capable of improving load leakage detection performance and installation method thereof - Google Patents

Abstract

The invention relates to a single-phase transformer system capable of improving load leakage detection performance and an installation method thereof, comprising the following steps: a single-phase two-wire transformer, a site grounding grid, a grounding wire and a leakage monitoring CT; one end of the grounding wire is connected with the site grounding network, and the other end of the grounding wire is connected with one secondary wiring terminal of the single-phase two-wire transformer and is used for establishing a leakage current loop and a zero-ground voltage release channel; the leakage monitoring CT is sleeved on two power supply wires of the load side of the single-phase two-wire system transformer and is used for detecting leakage current data. The invention enables the leakage current to have a return channel, the leakage current detection equipment can detect the leakage current, the leakage current is reported to operators on duty through the monitoring terminal, the basis is provided for the follow-up leakage detection, the zero ground voltage is eliminated, the occurrence of the event that the zero ground voltage is impacted to damage electronic equipment such as RTU and the like is avoided, and the method is safe and reliable and does not influence the normal operation of the original line load.

Description

Single-phase transformer system capable of improving load leakage detection performance and installation method thereof

Technical Field

The invention belongs to the technical field of electric power engineering, and relates to a single-phase transformer system and an installation method thereof, in particular to a single-phase transformer system and an installation method thereof which can improve load leakage detection performance.

Background Art

Street lights are the most numerous public facilities in cities. The safe operation of street light facilities is closely related to the safety of people's lives, especially during the flood season. Waterlogging on roads poses a great threat to the safe operation of street light equipment. When a lamp pole leaks electricity, if it is not discovered and managed in time, it will lead to great safety hazards. The large number and wide distribution of lamp poles restrict the efficiency and accuracy of manpower inspections, so the addition of remote equipment monitoring and alarm functions becomes very important.

However, the current operation mode of the suspension system of the single-phase two-wire transformer makes it impossible to monitor the leakage situation, and there are also the following problems.

1. The current street lamp transformer is a single-phase two-wire transformer. Both ends of the transformer low-voltage output side are suspended (not grounded). Since the transformer is completely isolated from the ground wire, the zero-ground voltage cannot be released. At the same time, there is no loop between the ground and the lamp pole. When the lamp pole leaks, the leakage detection device cannot detect the leakage current.

2. The normal voltage between the two low-voltage terminals of a single-phase transformer and the ground is 0.23kV, but sometimes it is as high as 1kV or more. If it is assumed that the two ends of the output are the live wire and the neutral wire respectively, the voltage to the ground is regarded as the zero-to-ground voltage. When the output generates a higher zero-to-ground voltage, since the transformer is completely isolated from the ground wire, the zero-to-ground voltage cannot be released. In the current power supply state, the zero-to-ground voltage must exist. Although this voltage will not shock people, it has a great impact on some electronic equipment and is easy to damage electronic equipment such as leakage remote monitoring equipment.

After searching, no prior art documents identical or similar to the present invention were found.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a single-phase transformer system and an installation method thereof that can improve the load leakage detection performance, so that the leakage current has a return channel and the leakage detection device can detect the leakage current.

The present invention solves the practical problem by adopting the following technical solutions:

A single-phase transformer system capable of improving load leakage detection performance comprises: a single-phase two-wire transformer, a site grounding grid, a grounding wire and a leakage monitoring CT; one end of the grounding wire is connected to the site grounding grid, and the other end is connected to one of the secondary wiring terminals of the single-phase two-wire transformer, so as to establish a leakage current loop and a zero-ground voltage release channel; the leakage monitoring CT is mounted on two power supply wires on the load side of the single-phase two-wire transformer, so as to detect leakage current data.

Moreover, the output end of the leakage monitoring CT is also connected to a leakage monitoring remote monitoring terminal, and the leakage monitoring remote monitoring terminal is used to output the collected leakage current data to the monitoring platform.

Moreover, the leakage monitoring CT is a high-precision current transformer of milliampere level.

Moreover, the neutral line is made of copper bus or cable at the output end.

A method for installing a single-phase transformer system capable of improving load leakage detection performance comprises the following steps:

Step 1. Select the phase for transformation on the low-voltage side of the single-phase transformer. Before the transformation, use a multimeter to test the phase-to-ground voltage of the two phases of the transformer. If the phase-to-ground voltage of the two phases is about 110V, you can choose one phase as the transformation phase; if there is a phase-to-ground voltage of 0V, then perform grounding transformation on this phase;

Step 2: Ensure that the grounding is reliable. Before the transformation is implemented, make sure that the grounding resistance in the station is no more than 10 ohms, and the grounding resistance of the station lamp pole load equipment is no more than 4 ohms. If it is lower than this standard, the grounding resistance needs to be further reduced;

Step 3: Select a grounding wire or grounding bar with sufficient current carrying capacity according to the actual situation of the transformation site;

Step 4: Take safety measures on site and shut down the power supply of the site to be renovated for electrical inspection and grounding;

Step 5: Set one of the two output terminals of the single-phase transformer as the phase line and the other as the neutral line. Connect the two ends of the grounding wire to the station pole first and then to the transformer terminal to ground the neutral line.

Step 6: Install the street lamp intelligent control terminal and install a leakage transformer in the power supply circuit;

Step 7: Remove the ground wire, restore power supply, and debug the "four remote control" functions of the monitoring terminal.

Advantages and beneficial effects of the present invention:

1. The present invention provides a single-phase transformer system and an installation method thereof that can improve the load leakage detection performance. A grounding wire is added to the secondary terminal of the single-phase transformer, and the two power supply lines on the load side are both set in the same high-precision CT. At the same time, the grounding of each lamp pole is ensured to be reliable. After the transformation, the leakage current has a return channel. The leakage detection equipment can detect the leakage current and report it to the on-duty personnel through the monitoring terminal, providing a basis for subsequent leakage investigation. At the same time, the zero-ground voltage is eliminated to avoid the occurrence of zero-ground voltage shock damaging RTU and other electronic equipment. This method is safe and reliable and will not affect the normal operation of the original line load.

2. After the transformation of the present invention, the zero-ground voltage of the original system will not be offset, avoiding the occurrence of the problem of excessive zero-sequence voltage impacting electronic equipment, further ensuring the safe and stable operation of automated electronic equipment in the street lamp system, ensuring that the street lamp equipment can realize the "four remote" functions of telemetry, telesignaling, teleadjustment, and remote control, and enhancing the flexibility of street lamp opening and closing control, real-time status monitoring, and reliability of remote emergency opening and closing, greatly improving operational efficiency and promoting urban development.

3. The present invention, by transforming the single-phase two-wire transformer, establishes a leakage current loop and a neutral-ground voltage release channel, and is equipped with a leakage remote monitoring device and system, so that the original system can be enhanced with a leakage monitoring function. When leakage current occurs, it can be discovered at the first time and timely treated to avoid leakage injury incidents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a single-phase transformer power supply system of the present invention;

FIG2 is a schematic diagram of the current operation mode of the single-phase transformer of the present invention;

FIG3 is a schematic diagram of the operation mode of the single-phase transformer after transformation of the present invention;

FIG4 is a schematic diagram of the experimental wiring method of the single-phase transformer before transformation of the present invention;

FIG. 5 is a schematic diagram of the experimental wiring method after the single-phase transformer of the present invention is modified.

DETAILED DESCRIPTION

The embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

A single-phase transformer system capable of improving load leakage detection performance, as shown in FIGS. 1 to 3, comprises: a single-phase two-wire transformer, a site grounding grid, a grounding wire and a leakage monitoring CT (i.e., the leakage transformer in FIGS. 2 and 3); one end of the grounding wire is connected to the site grounding grid, and the other end is connected to one of the secondary wiring terminals of the single-phase two-wire transformer, so as to establish a leakage current loop and a zero-ground voltage release channel; the leakage monitoring CT is mounted on the two power supply wires on the load side of the single-phase two-wire transformer, so as to detect leakage current data.

The output end of the leakage monitoring CT is also connected to a leakage monitoring remote monitoring terminal, and the leakage monitoring remote monitoring terminal is used to output the collected leakage current data to a monitoring platform.

The leakage monitoring CT is a high-precision current transformer of milliampere level.

The neutral line is a copper bus or a cable at the output end.

In this embodiment, the present invention is further described in conjunction with the accompanying drawings:

Fig. 1 is a diagram of the power supply system of a single-phase transformer of the present invention, including an existing single-phase two-wire transformer, a reliable grounding network in the station, and a newly added reliable grounding wire, one end of which is connected to one of the secondary terminals of the transformer, and the other end is reliably connected to the station grounding network; a newly added high-precision CT, both load-side power supply lines are set in the same high-precision CT, and the high-precision CT is used in conjunction with the existing pole-by-pole grounding method of street lamp poles to establish a leakage current loop and a zero-ground voltage release channel, and a synchronously matched leakage monitoring remote monitoring terminal is used, so that the problems found can be fed back in the first time to guide the on-duty personnel to take measures.

Among them, the grounding resistance inside the station is not more than 10 ohms, the protective grounding resistance on the lamp pole side is not more than 4 ohms, and the leakage monitoring CT uses high-precision products.

As shown in Figure 2 and Figure 3, they are the current operation mode and the operation mode after the transformation. After various primary and secondary tests on the transformer, the voltage and current data show that the transformation will not affect the system operation. Before the transformation, the leakage current transformer did not detect data, but after the transformation, the leakage current value can be detected. The results prove that the transformation plan is feasible.

In order to ensure the feasibility of the solution during the implementation of the present invention, an isolation transformer with the same principle is first selected for laboratory testing, and the experimental wiring is shown in Figures 4 and 5.

In this embodiment, a resistor with a human body resistance range of 1000Ω-1500Ω in daily environment is selected to simulate a human body electric shock injury scenario.

After various primary and secondary tests on the transformer, the detected voltage and current data showed that the modification would not affect the system operation.

Before the transformation, the leakage current transformer in Figure 4 did not detect data, but after the transformation, the leakage current value can be detected in Figure 5. The results prove that the transformation plan is feasible.

A method for installing a single-phase transformer system capable of improving load leakage detection performance comprises the following steps:

Step 1. Select the phase for transformation on the low-voltage side of the single-phase transformer. Before the transformation, use a multimeter to test the phase-to-ground voltage of the two phases of the transformer respectively. If the phase-to-ground voltage of the two phases is about 110V, you can select any phase as the transformation phase; if one phase has a ground voltage of 0V, it means that there is serious grounding in the 0V voltage phase load line of this station, and this phase should be grounded.

Step 2: Ensure that the grounding is reliable. Before the transformation is implemented, make sure that the grounding resistance in the station is no more than 10 ohms, and the grounding resistance of the station lamp pole load equipment is no more than 4 ohms. If it is lower than this standard, the grounding resistance needs to be further reduced.

Step 3: Select a grounding wire or grounding bar with sufficient current carrying capacity according to the actual situation of the reconstruction site.

Step 4: Take on-site safety measures and shut down the power supply and conduct grounding inspection at the site to be renovated.

Step 5: Set the two output ends of the single-phase transformer as the phase line and the neutral line. Connect the two ends of the grounding wire to the station pole first and then to the transformer terminal to ground the neutral line.

Step 6: Install the street lamp intelligent control terminal and install a leakage transformer in the power supply circuit.

Step 7: Remove the ground wire, restore power supply, and debug the "four remote control" functions of the monitoring terminal.

The present invention also analyzes the risk points in the transformation process and takes precautions against risks in advance during the transformation implementation process. The analysis is as follows:

The transformation plan changes the original isolation operation characteristics. To solve the zero-ground voltage problem, the zero-ground short circuit must be made at the output end of the single-phase transformer. However, due to the zero-ground short circuit at the output end of the single-phase transformer, the complete ground isolation function is lost. If a person standing on the ground touches the live wire at the output end of the transformer, it will cause electric shock. Therefore, before the experiment, it is necessary to ensure that the insulation of the transformation line is good and the grounding of the lamp pole is reliable. And adjust the corresponding protection equipment specifications and values according to the line load conditions.

For the two output ends of the original single-phase transformer, one is set as the phase line and the other as the neutral line; the neutral line of the original single-phase transformer can be directly grounded at the output end using a copper bus or cable, and the grounding wire must be reliably connected.

After the grounding wire is installed, it is strictly forbidden to remove the grounding wire manually when the transformer is in operation. Otherwise, personal safety accidents or damage to electrical equipment may occur during the removal process.

Carry out ground resistance test according to the specification requirements. If the resistance value does not meet the requirements, measures should be taken to reduce the ground resistance and then test again until it meets the requirements.

Before the transformation, the phase-to-ground voltage of the transformer should be determined, and the phase-to-ground voltage of the two phases of the transformer should be tested separately with a multimeter (it should be around 110V under normal circumstances). If one phase is 0, it means that the 0V voltage phase of this station has been seriously grounded, and this phase should be grounded. The other phase should not be modified, otherwise it will cause a phase-to-phase short circuit fault.

The working principle of the present invention is:

When in use, the leakage monitoring CT can monitor the leakage in the line in time. Good lamp pole grounding and station protection setting can ensure that the problem is isolated in the first time to avoid electric shock. At the same time, the leakage remote monitoring equipment transmits the collected data to the duty personnel. After the monitoring duty personnel learn about the leakage problem, they can take timely measures to improve the efficiency of defect elimination.

It should be emphasized that the embodiments of the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation modes. Any other implementation modes derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims (4)

1. An installation method of a single-phase transformer system capable of improving load leakage detection performance is characterized in that: the method comprises the following steps:

Step 1, selecting a low-voltage side reconstruction phase of a single-phase transformer, respectively testing the ground voltages of two phases of the transformer by using a universal meter before reconstruction, and optionally selecting one phase as the reconstruction phase if the ground voltages of the two phases are about 110 v; if the condition that the ground voltage of one phase is 0V exists, the phase is grounded;

Step 2, determining that the grounding is reliable, determining that the grounding resistance in the station is not more than 10 ohms before modification, determining that the grounding resistance of the station lamp post load equipment is not more than 4 ohms, and continuously reducing the grounding resistance if the grounding resistance is lower than the standard;

step 3, selecting a grounding wire or a grounding row with sufficient current-carrying capacity according to the actual condition of the reconstruction station;

Step 4, making site safety measures, and carrying out power failure electricity test grounding on the transformed site;

Step 5, setting one of two output ends of the single-phase transformer as a phase line and the other as a neutral line, and grounding the neutral line according to the sequence that the two ends of the ground line are connected with the internal earth electrode of the station firstly and then connected with the transformer terminal;

step 6, installing an intelligent control terminal of the street lamp, and sleeving a leakage transformer in a power supply loop;

Step 7, removing the ground wire, recovering power transmission, and debugging the four-remote function of the monitoring terminal;

The single-phase transformer system capable of improving load leakage detection performance comprises: a single-phase two-wire transformer, a site grounding grid, a grounding wire and a leakage monitoring CT; one end of the grounding wire is connected with the site grounding network, and the other end of the grounding wire is connected with one secondary wiring terminal of the single-phase two-wire transformer and is used for establishing a leakage current loop and a zero-ground voltage release channel; the leakage monitoring CT is sleeved on two power supply wires of the load side of the single-phase two-wire system transformer and is used for detecting leakage current data.

2. The method for installing a single-phase transformer system for improving load leakage detection performance according to claim 1, wherein: the output end of the leakage monitoring CT is also connected with a leakage monitoring remote monitoring terminal, and the leakage monitoring remote monitoring terminal is used for outputting the collected leakage current data to a monitoring platform.

3. The method for installing a single-phase transformer system for improving load leakage detection performance according to claim 1, wherein: and the leakage monitoring CT selects a high-precision current transformer with the milliamp level.

4. The method for installing a single-phase transformer system for improving load leakage detection performance according to claim 1, wherein: the neutral line is a copper bar or a cable at the output end.