A power distribution area electric leakage current detection device and an electric leakage fault detection method

Abstract

The application relates to the technical field of fault detection, and discloses a transformer area electric leakage current detection device and an electric leakage fault detection method. The device collects phase voltage through a fixed measurement device to determine a fault phase conductor, and analyzes a fault path by combining current changes before and after the on-off of a relay switch, so that the device can realize rapid and accurate positioning of a grounding fault under a continuous power supply condition. The mobile measurement device can test a single conductor, avoids the opening degree limitation of an open mutual inductor, and significantly improves the searching efficiency and power supply reliability.

Description

Technical Field

[0001] This invention relates to the field of fault detection technology, specifically to a transformer substation leakage current detection device and a leakage fault detection method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In the operation and maintenance of 0.4kV low-voltage power networks, grounding faults are a common and widespread type of fault. Especially in rural areas, due to the large coverage area of ​​a single transformer, numerous low-voltage network branches, and dispersed power consumption points, locating a grounding fault is often time-consuming, labor-intensive, and inefficient, severely impacting fault handling speed and power supply reliability. There is an urgent need for a technical means that adapts to the complex rural power grid structure, improves location efficiency, ensures operational safety, and minimizes the impact of power outages on users, to assist power maintenance personnel in quickly and accurately locating 0.4kV low-voltage grounding faults.

[0004] Currently, low-voltage grounding fault location mainly relies on manual inspections, handheld instrument testing, or alternative current source testing. Traditional manual, door-to-door inspections typically require workers to carry portable measuring tools such as multimeters to test voltage or current at different line nodes, and then determine the fault location through multiple comparative analyses. This method is not only tedious and repetitive, but the judgment results also heavily depend on the experience of the workers, lacking standardized criteria and prone to misjudgment. In rural power supply environments, due to numerous line branches, long paths, and dispersed equipment, the search cycle is often lengthy, consuming significant manpower and resources. Furthermore, the search process often requires multiple segmented power outages, affecting power supply continuity and user experience.

[0005] Furthermore, while existing handheld testing methods based on open-type leakage current transformers can directly sense the leakage current of a line, this method involves using a handheld instrument to thread the four wires (A, B, C, and N) of the low-voltage line through the transformer to induce the leakage current. However, due to the limited opening of the open-type transformer, it is not suitable for overhead low-voltage lines with large conductor spacing. This method also requires on-site segment-by-segment testing, which is labor-intensive, inefficient, and poses significant safety risks when working on poles, at heights, or at night. Another testing method using voltage and current substitution devices measures leakage current by connecting an external known current source to replace the original circuit. This can improve testing accuracy to some extent, but this method requires disconnecting the original power supply, making it impossible to implement on lines under load, resulting in power outages. Additionally, this method requires testers to be extremely familiar with the network structure and load distribution; otherwise, misjudgments are likely. Moreover, the preparation work is complex, and the equipment investment is high, making it difficult to promote in routine operation and maintenance. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a transformer substation leakage current detection device and a leakage fault detection method. By using a fixed measuring device to collect phase voltage data to determine the faulty phase conductor, and combining this with current changes before and after the relay switch is turned on and off to analyze the fault path, rapid and accurate location of grounding faults is achieved without power interruption. The mobile measuring device can test single conductors, avoiding the limitations of open-ended current transformers and significantly improving fault location efficiency and power supply reliability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: One or more embodiments provide a transformer area leakage current detection device, including a fixed measuring device and a moving phase current measuring device. The fixed measuring device includes a power acquisition and transmission module, a remote control switch and a relay switch. The power acquisition and transmission module is connected to the line under test and is used to acquire the phase voltage of the connected measurement line and the current at the grounding point of the relay switch. The remote control switch is used to receive control commands from the mobile terminal and control the on / off state of the relay switch. The two ends of the relay switch are connected to the neutral point grounding wire and grounding electrode of the transformer under test, and are used to control the on / off state of the transformer neutral point grounding circuit. The grounding fault point can be located by measuring the change in phase current using a moving phase current measuring device before and after the neutral point grounding circuit of the transformer is switched on and off.

[0008] One or more embodiments provide a leakage current fault detection method, including the following steps: Connect the terminal block to any phase conductor of the circuit under test, collect the voltage to ground of each phase conductor in real time, and identify the faulty phase. Connect the measuring terminal of the terminal block to the set position on the faulty phase; set the moving phase current measuring device in the direction of the current at the branch point of the faulty phase to measure the current. The remote control relay switch operates. When the neutral point grounding wire and grounding electrode of the transformer under test are connected and disconnected, the moving phase current measuring device measures the current of each branch after the branch point. When the branch current changes before and after the relay switch operates, the corresponding branch is identified as the fault circuit branch. The moving phase current measuring device is moved to the next branch point according to the fault circuit branch to perform the next measurement; until the branch current of all measured branches remains unchanged before and after the relay switch is activated, the ground fault section is obtained.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: In this embodiment, the fixed measuring device is connected to the line under test at a certain point on the line. First, by collecting the phase voltage of each phase conductor, the phase conductor of the line with the ground fault is directly determined. The input end of the fixed measuring device is connected to the phase conductor with the fault and the current of the line at the back end is measured. The neutral point grounding wire of the transformer of the line under test and the actual grounding electrode are connected through the relay switch 5. By measuring the change of the current before and after connection, the line branch of the fault point can be determined, which can achieve rapid measurement. During the measurement process, the moving phase current measuring device can measure a single conductor, thus avoiding the problem of limited opening of the open current transformer. At the same time, the entire measurement process does not require power interruption. It only controls the on / off state of relay switch 5 and measures the phase current before and after the on / off state. This enables logical analysis and accurate judgment of the ground fault path without power interruption, greatly shortens the fault location time, avoids the impact of frequent power outages on the continuity of power supply to users, and improves fault handling efficiency and grid operation reliability.

[0010] The advantages of the present invention, as well as its additional advantages, will be described in detail in the following specific embodiments. Attached Figure Description

[0011] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute a limitation thereof.

[0012] Figure 1 This is a schematic diagram of the structure of the fixed measuring device according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the leakage current detection device for transformer substations according to Embodiment 1 of the present invention. Figure 3 This is a measurement example diagram of the leakage current detection device for transformer substations according to Embodiment 1 of the present invention; The components include: 1. Wiring terminals; 2. Power acquisition and transmission module; 3. Remote control switch; 4. Display device; 5. Relay switch; 6. Second current transformer; 7. First current transformer; 8. Neutral grounding wire of the transformer under test. Detailed Implementation

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0015] It should be noted that the terminology used herein is for describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. It should be noted that, without conflict, the various embodiments and features within those embodiments can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0016] Example 1 In one or more of the technical solutions disclosed in the embodiments, such as Figures 1 to 3 As shown, a transformer area leakage current detection device includes: a fixed measuring device and a moving phase current measuring device. The fixed measuring device includes a power acquisition and transmission module 2, a remote control switch 3 and a relay switch 5. The power acquisition and transmission module 2 is connected to the line under test and is used to acquire the phase voltage of the connected measurement line and the current at the grounding point of the relay switch 5. The remote control switch 3 is used to receive control commands from the mobile terminal and control the on / off state of the relay switch 5. The two ends of the relay switch 5 are connected to the neutral point grounding wire 8 and the grounding electrode of the transformer under test. It is used to control the on / off state of the transformer neutral point grounding circuit and realize the TT / IT mode switching. Based on the changes in phase current measured by the moving phase current measuring device before and after the neutral point grounding circuit of the transformer is turned on and off, the grounding fault point can be located. In this embodiment, the fixed measuring device is connected to the line under test at a certain point on the line. First, by collecting the phase voltage of each phase conductor, the phase conductor of the line with the ground fault is directly determined. The input end of the fixed measuring device is connected to the phase conductor with the fault to measure the current of the line at the back end. The neutral point grounding wire 8 of the transformer of the line under test is connected to the actual grounding electrode through the relay switch 5. By measuring the change of the current before and after connection, the line branch of the fault point can be determined, which can achieve rapid measurement. During this measurement process, the moving phase current measuring device can measure a single conductor, thus avoiding the problem of limited opening of the open current transformer. At the same time, the entire measurement process does not require power interruption. Only the on / off state of relay switch 5 is controlled, and the phase current is measured before and after the on / off state. This enables logical analysis and accurate judgment of the ground fault path without power interruption, greatly shortening the fault location time, avoiding the impact of frequent power outages on the continuity of power supply to users, and improving fault handling efficiency and grid operation reliability.

[0017] Specifically, in the IT state, if the neutral point grounding is disconnected, even if a phase is grounded, the leakage current is approximately zero because the current path is not closed; the relay switch 5 disconnects the neutral point grounding wire 8 and the grounding electrode of the transformer under test, corresponding to the IT state; in the TT state, the transformer's neutral point is grounded, and once a grounding fault occurs, the leakage current will flow back to the neutral point and then be released through the grounding electrode, and the current transformer can detect a significant current change; the relay switch 5 connects the neutral point grounding wire 8 and the grounding electrode of the transformer under test, corresponding to the TT state. In some embodiments, the wiring terminal 1 of the fixed measuring device includes a measuring terminal and a power terminal. The measuring terminal is connected to the phase conductor of the measuring circuit through a voltage transformer, and the power terminal includes a live wire and a ground wire connection terminal. like Figure 1 As shown, in this embodiment, the measuring terminal is set as terminal A1, which is connected to one of the live wires to connect to the phase wire being measured; the power supply terminals are set as terminal A2 and terminal N, which are respectively connected to the remaining live wires and the neutral wire to form a working power supply, and always maintain a 220V voltage output. The power acquisition and transmission module 2 is used to acquire the live wire to ground voltage and the ground fault current data acquired by the current transformer. The power acquisition and transmission module 2 can be equipped with a wireless communication module to transmit the acquired signals to a remote terminal or server via a wireless network for staff to analyze and refer to.

[0018] Specifically, the remote control switch 3 receives the control signal from the set mobile terminal and controls the relay switch 5 to close and open, thereby realizing the switching control of the voltage test circuit of the conductor to be measured and the neutral point grounding wire of the transformer. A further technical solution is that a first current transformer 7 is installed on the line connecting the relay switch 5 to the neutral point grounding wire 8 of the transformer under test, and a second current transformer 6 is connected on the connection line between the relay switch 5 and the grounding electrode; the second current transformer 6 is connected to the power acquisition and transmission module 2 and is used to measure the current at the grounding point of the relay switch 5. Furthermore, the fixed measuring device also includes a display device 4 for displaying the measured phase voltage and grounding current. The display device 4 is electrically connected to the first current transformer 7 and the power acquisition and transmission module 2, respectively.

[0019] In this embodiment, the first current transformer 7 is connected to the display device for local display, and the second current transformer 6 is connected to the power acquisition and transmission module 2 to upload remote data.

[0020] Optionally, the mobile phase current measuring device includes a mobile terminal and a current measuring component, which may be a clamp-on ammeter or a high-altitude clamp-on ammeter supported by an insulating rod.

[0021] Furthermore, the method for locating the ground fault point based on the change in phase current measured by the moving phase current measuring device before and after the switching on and off of the transformer neutral point grounding circuit includes the following steps: Step 1: Connect terminal 1 to any phase conductor of the circuit under test, and collect the voltage to ground of each phase conductor in real time to identify the faulty phase. Specifically, if the measured voltage is close to 380V, the phase is determined to be a non-faulty phase; if the measured voltage is close to 0V, the phase is determined to be a faulty phase with a ground fault. Based on this, the ground fault phase is identified. Once the faulty phase is identified, the next step is to locate the ground fault.

[0022] Step 2: Connect the measuring terminal of terminal 1 to the set position on the faulty phase; set the moving phase current measuring device in the direction of the current at the branch point of the faulty phase to measure the current. Step 3: Remotely control the relay switch 5 to operate. When the neutral point grounding wire 8 and the grounding electrode of the transformer under test are connected and disconnected, the moving phase current measuring device measures the current of each branch after the branch point. When the branch current changes before and after the relay switch 5 is operated, the corresponding branch is identified as the fault circuit branch. Step 4: Move the moving phase current measuring device to the next branch point according to the fault circuit branch and perform the next measurement; until the branch current of all measured branches remains unchanged before and after the relay switch 5 is activated, the ground fault section is obtained. Furthermore, the fault section is divided into multiple smaller segments. The moving phase current measuring device is set sequentially at the starting position of each segment according to the current direction. The current at each starting position is measured when the relay switch 5 is closed and opened. If the measured current changes when the relay switch 5 is closed and opened, the device continues to move to the next segment for measurement. Otherwise, the grounding fault is in the current segment, and the fault is directly investigated.

[0023] Example 2 Based on Embodiment 1, and the leakage current detection device for transformer substations described in Embodiment 1, this embodiment provides a leakage fault detection method, including the following steps: Step 1: Connect terminal 1 to any phase conductor of the circuit under test, and collect the voltage to ground of each phase conductor in real time to identify the faulty phase. Specifically, if the measured voltage is close to 380V, the phase is determined to be a non-faulty phase; if the measured voltage is close to 0V, the phase is determined to be a faulty phase with a ground fault. Based on this, the ground fault phase is identified. Once the faulty phase is identified, the next step is to locate the ground fault.

[0024] Step 2: Connect the measuring terminal of terminal 1 to the set position on the faulty phase; set the moving phase current measuring device in the direction of the current at the branch point of the faulty phase to measure the current. Step 3: Remotely control the relay switch 5 to operate. When the neutral point grounding wire 8 and the grounding electrode of the transformer under test are connected and disconnected, the moving phase current measuring device measures the current of each branch after the branch point. When the branch current changes before and after the relay switch 5 is operated, the corresponding branch is identified as the fault circuit branch. Specifically, control commands are issued through a handheld terminal to control the remote control switch 3 to turn the relay switch 5 on or off, thereby connecting or disconnecting the connection circuit between the neutral point grounding wire of the transformer under test and the grounding electrode, thus forming TT and IT grounding systems respectively.

[0025] Furthermore, by comparing the trend of leakage current before and after the relay switch 5 is turned on, if the current is significantly increased after the grounding circuit is connected in a certain path, it is determined that the path is a branch line with a grounding fault. Step 4: Move the moving phase current measuring device to the next branch point according to the fault circuit branch and perform the next measurement; until the branch current of all measured branches remains unchanged before and after the relay switch 5 is activated, the ground fault section is obtained. The method in this embodiment automatically identifies the ground fault phase by collecting the voltage to ground of each phase conductor. It combines a fixed measuring device with a remotely controlled relay switch to construct a dynamic switching mechanism for the grounding mode, enabling logical judgment of the fault path without interrupting power supply. By comparing the current changes in each branch after the branch point before and after the relay switch is turned on and off, the path through which the fault current flows can be quickly identified, significantly narrowing the scope of investigation.

[0026] The adoption of a mobile phase current measuring device enables current detection of a single conductor, avoiding the incompatibility issues caused by the large spacing between conductors in traditional open-type current transformers in overhead lines, thus improving system applicability and ease of operation. Combined with the current change trend data uploaded by the device, an integrated detection process can be achieved for identifying ground fault phases, analyzing their paths, and locating fault sections. This eliminates the need for power outages and frequent disassembly and reassembly of testing equipment, significantly improving the efficiency of ground fault location and the reliability of power grid operation.

[0027] A specific test example, such as Figure 2 As shown, the fixed measuring device in this embodiment is fixedly installed at any point on the line. It first measures the phase voltage. When the phase voltage approaches zero, it continues to connect the faulty phase for the next measurement. Subsequent measurements only measure the faulty phase. Figure 2Assuming the faulty phase is phase C, a handheld moving phase current measuring device is used to reach the first branch. The current in the upward branch and the current in the right branch of phase C at the branch point C1 are measured. When relay switch 5 is connected, the measured current loop is as follows: Figure 2 As shown by the red dashed line, the fault current is 0 when disconnected and greater than zero when connected. Therefore, the current measured on the fault current discharge circuit corresponding to phase C will change significantly when the fault current discharge circuit is connected and disconnected, thus identifying the branch with fault current. Figure 2 In the C1 backend branch, the rightward branch is identified as the faulty branch; Continue measuring the current of the branch connected to the rear end of the next branch point C2. The downward branch is the fault branch, which allows us to locate the fault section between the two branch points. In step 4, the obtained fault section is the conductor section between one branch point and another. Further, the fault section is divided into multiple small segments. The moving phase current measuring device is set at the starting position of each small segment in sequence according to the current direction. The current at the starting position of each small segment is measured when the relay switch 5 is closed and opened. If the measured current change when the relay switch 5 is closed and opened is found, the device continues to move to the next small segment for measurement. Otherwise, the grounding fault is in the current small segment, and the fault is directly investigated. like Figure 3 The example shown, Figure 3 The square box represents the meter box, and the circle represents the tower. At the start of the test, the measuring device is fixed near tower G1, and the voltage to ground of the three phase conductors is sampled first. When the voltage to ground of one phase conductor is close to 0V, while the voltage to ground of the other two phases rises to about 380V, it can be determined that the phase conductor close to 0V is the line phase conductor that has experienced a ground fault.

[0028] Maintenance personnel carried a portable phase current measuring device and sequentially tested the leakage current of each branch path along the faulty phase line. Figure 3 Taking the path as an example, the measurement path passes through G1→G2→G3→G4 in sequence, and the current test analysis is performed on the branch after each "T" contact along the path.

[0029] For example, there are three branches at node G2, leading to node G3 and other directions respectively. Maintenance personnel use a clamp meter on the faulty phase conductor of G2 to measure the faulty phase current values ​​in G2→G3 (upward) and G2→other directions (horizontal right and left), and control relay switch 5 to connect the neutral point grounding loop through a remote handheld terminal to form a complete leakage current path.

[0030] If the fault current measured in a certain branch changes before and after the relay switch 5 is turned on, then that branch is the actual path through which the leakage current flows. by Figure 3For example, a significant change in fault current was detected in the path above G2 (G2→G3→G4), indicating that there was a grounding fault point in this path. The user meter box at the end of the J1 branch on the left side of G4 was finally located as the suspected grounding point.

[0031] This method allows for rapid troubleshooting and narrowing down of the fault range by measuring only the faulty phase branch segment by segment, avoiding the tedious process of powering off the entire line and manually checking the whole line. It achieves a closed-loop positioning process of phase selection, segment selection, branch selection, and point location.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0033] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for detecting leakage current faults, characterized in that: Using a transformer substation leakage current detection device includes the following steps: Connect the terminal block to any phase conductor of the circuit under test, collect the voltage to ground of each phase conductor in real time, and identify the faulty phase. Connect the measuring terminal of the wiring terminal to the set position on the faulty phase; The moving phase current measuring device is set at the branch point of the faulty phase in the direction of the current to measure the current; The remote control relay switch operates. When the neutral point grounding wire and grounding electrode of the transformer under test are connected and disconnected, the moving phase current measuring device measures the current of each branch after the branch point. When the branch current changes before and after the relay switch operates, the corresponding branch is identified as the fault circuit branch. The moving phase current measuring device is moved to the next branch point according to the fault circuit branch to perform the next measurement; until the branch current of all measured branches remains unchanged before and after the relay switch is activated, the ground fault section is obtained. The leakage current detection device for the transformer area includes a fixed measuring device and a moving phase current measuring device. The fixed measuring device includes a power acquisition and transmission module, a remote control switch, and a relay switch. The power acquisition and transmission module is connected to the line under test and is used to acquire the phase voltage of the connected measurement line and the current at the grounding point of the relay switch. The remote control switch is used to receive control commands from the mobile terminal and control the on / off state of the relay switch. The two ends of the relay switch are connected to the neutral point grounding wire and grounding electrode of the transformer under test, and are used to control the on / off state of the transformer neutral point grounding circuit. The grounding fault point can be located by measuring the change in phase current using a moving phase current measuring device before and after the neutral point grounding circuit of the transformer is switched on and off.

2. The leakage fault detection method as described in claim 1, characterized in that: The wiring terminals of the fixed measuring device include measuring terminals and power supply terminals. The measuring terminals are connected to the phase conductors of the measuring circuit through a voltage transformer, and the power supply terminals include live wire and ground wire connection terminals.

3. The leakage fault detection method as described in claim 1, characterized in that: The remote control switch receives control signals from the set mobile terminal and controls the closing and opening of the relay switch to realize the switching control of the voltage test circuit of the conductor to be measured and the neutral point grounding wire of the transformer.

4. The leakage fault detection method as described in claim 1, characterized in that: A first current transformer is installed on the line connecting the relay switch to the neutral point grounding wire of the transformer under test, and a second current transformer is installed on the connection line between the relay switch and the grounding electrode. The second current transformer is connected to the power acquisition and transmission module and is used to measure the current at the grounding point of the relay switch.

5. The leakage fault detection method as described in claim 1, characterized in that: The fixed measuring device also includes a display device, which is electrically connected to the first current transformer and the power acquisition and transmission module, respectively.

6. The leakage fault detection method as described in claim 1, characterized in that: The mobile phase current measuring device includes a mobile terminal and a current measuring component. The current measuring component adopts a clamp ammeter or a high-altitude clamp ammeter supported by an insulating rod.

7. The leakage fault detection method as described in claim 1, characterized in that: Connect the terminal block to any phase conductor of the circuit under test and collect the voltage to ground of each phase conductor in real time. If the measured voltage is close to 380V, the phase is determined to be a non-faulty phase. If the measured voltage is close to 0V, the phase is determined to be the faulty phase where a ground fault has occurred.

8. The leakage fault detection method as described in claim 1, characterized in that: By comparing the trend of leakage current before and after the relay switch is activated, if the current increases beyond the set threshold after the grounding loop is connected in a certain path, then the path is determined to be a branch line with a grounding fault.

9. The leakage fault detection method as described in claim 1, characterized in that: The fault section is divided into multiple smaller segments. Moving phase current measuring devices are sequentially set at the starting position of each segment according to the current direction. The current at the starting position of each segment is measured when the relay switch is closed and opened. If the measured current change when the relay switch is closed and opened is observed, the device continues to move to the next segment for measurement. Otherwise, the ground fault is in the current segment.

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