CN111308268A - A method and system for evaluating latent faults of distribution network equipment - Google Patents

Abstract

The application discloses an assessment method and system for latent faults of power distribution network equipment, and the assessment method and system are used for assessing latent faults of a power distribution network system.

Description

A method and system for evaluating latent faults of distribution network equipment

technical field

The present application relates to the technical field of distribution network state monitoring, and in particular, to a method and system for evaluating latent faults of distribution network equipment.

Background technique

As the link of supply and demand connecting the transmission network and power users, the distribution network belongs to the end of the power system and faces directly to users. It is an important public infrastructure serving people's livelihood. The reliability of its power supply directly affects the development of the national economy and the improvement of people's living standards. . With the rapid development of the economy, the total power consumption and the groups of power users are increasing rapidly, the complexity of the distribution network is getting higher and higher, and the types and numbers of distribution network equipment are increasing rapidly.

Most of my country's 6kV-35kV medium-voltage distribution networks use low-current grounding methods, and the structure is relatively complex. The length of distribution network lines accounts for about 90% of the length of power grid lines at all levels. Compared with high-voltage transmission lines, the probability of failure of medium-voltage distribution networks is much higher, and nearly 75% of user power outages are caused by medium-voltage distribution networks. The distribution network has complex structure, many branch nodes, large line capacitance, variable and flexible operation mode, harsh operating environment, and high frequency of faults.

The distribution network is composed of distribution substations, overhead lines, cables, towers, isolation switches, reactive power compensation capacitors and some auxiliary facilities. The basis of safe operation, the influence of equipment on the reliability level of distribution network cannot be ignored. The state assessment of the equipment insulation of the distribution network is carried out to detect the latent faults of the equipment insulation in advance, and after the transfer, the maintenance is carried out to improve the reliability of the power supply of the distribution network, reduce sudden accidents, and greatly reduce the pressure on the operation and maintenance personnel.

At present, in order to evaluate the status of the insulation of distribution network equipment and improve the reliability of power supply, a lot of research has been done in related fields.

The patent with the application number of 201110382596.2 discloses a condition maintenance control method of a distribution network equipment condition assessment system. The method judges whether the equipment under test is faulty by judging the leakage current of the arrester and the temperature of the cable joint, and formulates the maintenance plan. This method can perform on-line detection of the equipment under test, but the detection of leakage current and temperature of the cable head has low sensitivity and can not even be judged for defects such as local insulation deterioration and discharge of the arrester and the cable head.

The patent with the application number of 201811519232.2 discloses a movable platform for detecting a distribution network and relates to a distribution network detection device, which is composed of a movable carrier, a data processing module, a detection module, an integrated wiring module and a human-computer interaction module , which solves the problems of lack of mobility, low efficiency and long experimental cycle in traditional factories for cable experiments. However, the device can only detect cables, and the non-contact detection sensitivity is low.

The patent with the application number of 201910694071.9 discloses a switchgear state evaluation method and server, which can obtain infrared temperature measurement, switchgear inspection, partial discharge detection, and switchgear operation parameter monitoring for the switchgear, and determine the operation state of the switchgear according to the detection results. make an assessment. This method can only be detected under the operating voltage, the operating voltage is relatively low, the detection sensitivity to insulation deterioration and partial discharge is relatively low, and the state evaluation results are inaccurate.

At present, the commonly used methods for evaluating insulation latent faults of distribution network equipment are partial discharge monitoring methods, mainly including ultra-high frequency method and ultrasonic method to measure partial discharge. These methods are limited by their measurement principles and can only be qualitatively measured, not Quantitative measurement, and in the case of electrification, the measurement accuracy of the two methods is difficult to guarantee. On the other hand, the general partial discharge test is measured at a voltage higher than the normal operating voltage of the equipment. If it is under the normal operating voltage, the latent fault (mainly refers to the partial discharge phenomenon caused by the insulation defect of the equipment) is difficult to find.

To sum up, the partial discharge monitoring method is a widely used method to detect latent faults in the insulation of power equipment, but the low operating voltage of the distribution network itself to the ground greatly reduces the detection sensitivity of latent faults.

SUMMARY OF THE INVENTION

The present application provides a method and system for evaluating latent faults of distribution network equipment, so as to solve the problem of low detection sensitivity of the existing methods for evaluating latent faults of distribution network equipment.

In a first aspect, the present application provides a method for evaluating latent faults of distribution network equipment, including:

S100, select one phase of the three-phase lines A, B, and C in the distribution network system as the operating phase x, the other two phases are the phases y and z to be measured, and the operating phase voltage corresponding to the operating phase x is U _x , and the phase to be measured is U x . The phase voltages to be measured corresponding to the phases y and z are U _y and U _z , where x, y, z=A, B or C;

S200, obtaining the starting setting value ΔU ₀ , including reducing the phase voltage of the operating phase to zero, simulating the operating state when a single-phase grounding fault occurs in the distribution network system, measuring the voltage change of the neutral point before and after the fault, and calculating The voltage variation of the neutral point is used as the starting setting value ΔU ₀ of the PD detection module;

S300, perform multiple step-down operations on the operating phase voltage U _x , and measure the voltage variation U _i of the neutral point during each step-down operation, where i is the number of step-down times, i=1, 2...;

S400, sequentially determine whether the change amount U _i of the neutral point voltage during each voltage drop operation is equal to the starting setting value ΔU ₀ , and when U _i is equal to the starting setting value ΔU ₀ , measure the distribution network on the phases y and z to be measured Partial discharge of equipment;

S500, according to the partial discharge of the distribution network equipment on the phases y and z to be measured, determine whether the distribution network equipment on the phases y and z to be measured has a latent fault risk, and if there is a latent fault risk, the The safety state of distribution network equipment on phases y and z is demarcated as latent fault risk;

S600, changing the operation phase, and repeating steps S200-S400 until the three phases A, B, and C are all used as primary operation phases;

S700: Determine whether the safety state of the distribution network equipment on the A, B, and C three-phase lines is calibrated at least twice as a latent fault risk, if the distribution network equipment on the A, B, or C three-phase lines is calibrated at least twice For the latent fault risk, it is determined that there is a latent fault in the distribution network equipment on the A, B or C three-phase lines.

Optionally, S200, obtain the startup setting value ΔU ₀ , which specifically includes:

S210, operate the control switch, so that the x-phase voltage on the phase power supply generator corresponding to the operation phase x is connected to the neutral point;

S220, adjust the output voltage of the phase power supply generator to reduce the operating phase voltage U _x to U' _x , and calculate the first neutral point voltage as U ₀₁ =U _x -U'_x;

S230, the secondary regulation phase power supply generator reduces the operating phase voltage U _x to U" _x =0V, and calculates the second neutral point voltage as U ₀₂ =U _x -U "_x;

S240: Calculate the startup setting value ΔU ₀ according to the first neutral point voltage U ₀₁ and the second neutral point voltage U ₀₂ , where ΔU ₀ =U ₀₁ -U ₀₂ =U″ _x -U′ _x .

In a second aspect, the present application also provides an evaluation system for latent faults of distribution network equipment, which is used in a distribution network system. The distribution network system includes A, B, and C three-phase lines, including a phase power supply generator, The phase power supply generator is used to connect with the neutral point of the distribution network system, and the phase power supply generator includes A, B, C three-phase power supply lines, A, B, C three-phase power supply lines respectively generate and distribute power. The grid system voltages U _A , U _B and U _C have opposite phases and the same amplitude;

A control switch is set on the connection between the phase power supply generator and the neutral point of the distribution network system, and the control switch is used to control the corresponding connection of the A, B, and C three-phase power supply lines of the phase power supply generator. A, B, C three-phase lines on the distribution network system;

The evaluation system for latent faults of distribution network equipment further includes a fault evaluation device and a plurality of detection devices all connected to the evaluation device, the detection devices including three-phase coupling capacitors and all connected to the three-phase coupling capacitors The setting device and partial discharge monitoring device of the

The three-phase coupling capacitor is used for coupling the partial discharge signal of the distribution network equipment and the voltage value of the distribution network system;

The setting device includes:

The voltage acquisition module is used to acquire the voltage value of the distribution network system in real time;

The setting calculation module is used to calculate the starting setting value ΔU ₀ according to the neutral point voltage;

The setting judgment module is used to judge whether the change U _i of the neutral point voltage is equal to the starting setting value ΔU ₀ ;

a partial discharge starting module, configured to send a starting instruction to the partial discharge monitoring device;

The partial discharge monitoring device includes:

The partial discharge detection module is used to collect the partial discharge signal of the distribution network equipment;

a data transmission module for transmitting the partial discharge signal to the state evaluation device;

The evaluation system for latent faults of distribution network equipment further includes multiple sets of detection devices,

The fault assessment device specifically includes:

Communication module for receiving partial discharge signal;

The state calibration module is used to calibrate the safe state of the distribution network equipment on the A, B or C three-phase lines according to the partial discharge signal;

The fault determination module is used to determine whether there is a latent fault in the distribution network equipment on the A, B or C three-phase lines according to the safety status of the distribution network equipment.

Optionally, one end of the three-phase coupling capacitor is installed on the high voltage side of the distribution network equipment, and the other end is connected to the partial discharge monitoring device.

Optionally, one end of the partial discharge monitoring device is connected to the three-phase coupling capacitor, and the other end is grounded.

Optionally, the distribution of the several detection devices is as follows: on the lines of the power distribution network system, one detection device is provided at every preset distance.

The present application provides a method and system for evaluating latent faults of distribution network equipment, which are used to evaluate the latent faults of distribution network systems. A certain phase line is used as the operating phase. By reducing the phase voltage of the operating phase to zero, the operating state of the distribution network system when a single-phase ground fault occurs is simulated, and the voltage change of the neutral point before and after the fault is measured. Take the voltage variation of the neutral point as the starting setting value ΔU ₀ of the partial discharge detection module; then, perform multiple operations to reduce the phase voltage of the operating phase, and measure the neutral point voltage value U _i in the process, when U _i When it is equal to the starting setting value ΔU ₀ , measure the partial discharge of the distribution network equipment on the other two-phase lines; according to the measurement of the partial discharge of the distribution network equipment, determine whether the distribution network equipment on the two-phase line has a latent fault risk . After taking the three-phase A, B, and C as the primary operation phase in turn, count whether the safety status of the distribution network equipment on the A, B, and C three-phase lines has been demarcated as a latent fault risk at least twice. If A, B or C If the distribution network equipment on the three-phase line is rated as a latent fault risk at least twice, it is determined that the distribution network equipment on the A, B or C three-phase line has a latent fault.

In the process of latent fault assessment of distribution network equipment using the method or device of the present application, when the phase voltage of the operating phase is reduced, the phase voltages of the other two items will increase accordingly, and the higher voltage will act on the distribution network equipment. , if there is partial amplification in the distribution network equipment, the partial discharge quantity will also increase accordingly, and the larger partial discharge quantity is convenient for collection and fault analysis. It has high detection sensitivity for latent faults of distribution network equipment.

Description of drawings

In order to illustrate the technical solutions of the present application more clearly, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, without creative work, the Additional drawings can be obtained from these drawings.

FIG. 1 is a flowchart of an evaluation method for latent faults of distribution network equipment in the application;

FIG. 2 is an equivalent circuit diagram of an evaluation system for latent faults of distribution network equipment in the application;

FIG. 3 is a circuit diagram of an evaluation system for latent faults of distribution network equipment of the present application.

The symbols in Figure 1-3 are: 1-phase power supply generator, 2-control switch, 3-three-phase coupling capacitor, 4-partial discharge monitoring device, 5-fault evaluation device, 6-setting device.

Detailed ways

The present application provides a method for evaluating latent faults of distribution network equipment, which is used to evaluate the latent faults of a distribution network system. FIG. 1 is a flowchart of an evaluation method for latent faults of distribution network equipment in the application. As shown in FIG. 1 , the evaluation method for latent faults of distribution network equipment includes:

S100, select one phase of the three-phase lines A, B, and C in the distribution network system as the operating phase x, the other two phases are the phases y and z to be measured, and the operating phase voltage corresponding to the operating phase x is U _x , and the phase to be measured is U x . The phase voltages to be measured corresponding to the phases y and z are U _y and U _z , where x, y, z=A, B or C;

S200, obtaining the starting setting value ΔU ₀ , including reducing the phase voltage of the operating phase to zero, simulating the operating state when a single-phase grounding fault occurs in the distribution network system, measuring the voltage change of the neutral point before and after the fault, and calculating The voltage variation of the neutral point is used as the starting setting value ΔU ₀ of the PD detection module;

In this example, the startup setting value ΔU ₀ is obtained, which specifically includes,

S210, operate the control switch, so that the x-phase voltage on the phase power supply generator corresponding to the operation phase x is connected to the neutral point;

S220, adjust the output voltage of the phase power supply generator to reduce the operating phase voltage U _x to U' _x , and calculate the first neutral point voltage as U ₀₁ =U _x -U'_x;

S230, the secondary regulation phase power supply generator reduces the operating phase voltage U _x to U" _x =0V, and calculates the second neutral point voltage as U ₀₂ =U _x -U "_x;

S240: Calculate the startup setting value ΔU ₀ according to the first neutral point voltage U ₀₁ and the second neutral point voltage U ₀₂ , where ΔU ₀ =U ₀₁ -U ₀₂ =U″ _x -U′ _x .

S300 , performing multiple step-down operations on the operating phase voltage U _x , and measuring the voltage variation U _i of the neutral point during each step-down operation, where i is the number of step-down times, i=1, 2 . . . It should be noted that the working states of the distribution grid system under different voltages are simulated through multiple step-down operations. In addition, in order to prevent the occurrence of single-phase ground fault, the phase voltage U _x after the voltage drop operation process should be greater than zero.

S400, sequentially determine whether the change amount U _i of the neutral point voltage during each voltage drop operation is equal to the starting setting value ΔU ₀ , and when U _i is equal to the starting setting value ΔU ₀ , measure the distribution network on the phases y and z to be measured Partial discharge of equipment.

S500, according to the partial discharge of the distribution network equipment on the phases y and z to be measured, determine whether the distribution network equipment on the phases y and z to be measured has a latent fault risk, and if there is a latent fault risk, the The safe state of distribution network equipment on phases y and z is demarcated as latent fault risk.

It should be noted that judging whether the distribution network equipment has a latent fault risk is a technique commonly used by those skilled in the art according to partial discharge, and the specific implementation process will not be described in detail here.

S600 , changing the operation phase, and repeating steps S200 to S400 until the three phases A, B, and C are all used as primary operation phases.

S700: Determine whether the safety state of the distribution network equipment on the A, B, and C three-phase lines is calibrated at least twice as a latent fault risk, if the distribution network equipment on the A, B, or C three-phase lines is calibrated at least twice For the latent fault risk, it is determined that there is a latent fault in the distribution network equipment on the A, B or C three-phase lines.

The present application also provides an evaluation system for latent faults of distribution network equipment, which is used to evaluate the latent faults of the distribution network system, wherein the distribution network system includes A, B, and C three-phase lines.

FIG. 2 is an equivalent circuit diagram of an evaluation system for latent faults of distribution network equipment of the application, and FIG. 3 is a circuit diagram of an evaluation system for latent faults of distribution network equipment of the application. As shown in FIG. 2 and FIG. 3 , the distribution network The evaluation system of equipment latent fault includes a phase power supply generator 1, which is used for connecting with the neutral point of the distribution network system, and the phase power supply generator 1 includes A, B, C Three-phase power supply lines, A, B, C three-phase power supply lines respectively generate voltages with opposite phases and the same amplitude as the distribution network system voltages UA, UB and UC.

A control switch is provided on the connection between the phase power supply generator 1 and the neutral point of the distribution network system, and the control switch is used to control the corresponding three-phase power supply lines of A, B, and C of the phase power supply generator. Connect the A, B, C three-phase lines on the distribution network system.

The evaluation system for latent faults of distribution network equipment further includes a fault evaluation device and several detection devices connected to the evaluation device. The distribution of the several detection devices is: on the line of the distribution network system, each One of the detection devices is arranged at a preset distance.

The detection device includes a three-phase coupling capacitor 3 , a setting device 6 and a partial discharge monitoring device 4 both connected to the three-phase coupling capacitor 3 . Wherein, the three-phase coupling capacitor 3 is used for coupling the partial discharge signal of the distribution network equipment and the voltage value of the distribution network system. One end of the three-phase coupling capacitor 3 is installed on the high voltage side of the distribution network equipment, and the other end is connected to the setting device 6 and the partial discharge monitoring device.

The setting device 6 includes a voltage acquisition module, a setting calculation module, a setting judgment module and a partial discharge start module connected in sequence, wherein the voltage acquisition module is used to acquire the voltage value of the distribution network system in real time. The setting calculation module is used to calculate the starting setting value ΔU ₀ according to the neutral point voltage. The setting judgment module is used to judge whether the change U _i of the neutral point voltage is equal to the starting setting value ΔU ₀ . The partial discharge starting module is used to send a starting command to the partial discharge monitoring device. In actual use, when the change amount U _i of the neutral point voltage is equal to the starting setting value ΔU ₀ , it will send a starting command to the partial discharge monitoring device 4. The discharge monitoring device 4 collects the partial discharge signal of the distribution network equipment according to the start-up instruction.

One end of the partial discharge monitoring device 4 is connected to the three-phase coupling capacitor 3, and the other end is grounded. The partial discharge monitoring device 4 includes a partial discharge detection module and a data transmission module connected in sequence, wherein the partial discharge detection module is used to collect the partial discharge signal of the distribution network equipment, and the data transmission module is used to transmit the partial discharge signal to the state. evaluation device.

The evaluation system for latent faults of distribution network equipment further includes multiple sets of detection devices. The fault evaluation device 5 specifically includes a communication module, a state calibration module and a fault determination module connected in sequence, wherein the communication module is used for receiving partial discharge signals. The state calibration module is used to calibrate the safe state of the distribution network equipment on the A, B or C three-phase lines according to the partial discharge signal. The fault determination module is used to determine whether there is a latent fault in the distribution network equipment on the A, B or C three-phase lines according to the safety status of the distribution network equipment.

The present application provides a method and system for evaluating latent faults of distribution network equipment, which are used to evaluate the latent faults of distribution network systems. A certain phase line is used as the operating phase. By reducing the phase voltage of the operating phase to zero, the operating state of the distribution network system when a single-phase ground fault occurs is simulated, and the voltage change of the neutral point before and after the fault is measured. Take the voltage change of the neutral point as the starting setting value ΔU ₀ of the partial discharge detection module; then, perform multiple operations to reduce the phase voltage of the operating phase, and measure the neutral point voltage value Ui in the process, when Ui is equal to the start-up When the setting value ΔU ₀ , measure the partial discharge of the distribution network equipment on the other two-phase lines; according to the measurement of the partial discharge of the distribution network equipment, determine whether the distribution network equipment on the two-phase line has a latent fault risk. After taking the three-phase A, B, and C as the primary operation phase in turn, count whether the safety status of the distribution network equipment on the A, B, and C three-phase lines has been demarcated as a latent fault risk at least twice. If A, B or C If the distribution network equipment on the three-phase line is rated as a latent fault risk at least twice, it is determined that the distribution network equipment on the A, B or C three-phase line has a latent fault.

In the process of latent fault assessment of distribution network equipment using the method or device of the present application, when the phase voltage of the operating phase is reduced, the phase voltages of the other two items will increase accordingly, and the higher voltage will act on the distribution network equipment. , if there is partial amplification in the distribution network equipment, the partial discharge quantity will also increase accordingly, and the larger partial discharge quantity is convenient for collection and fault analysis. It has high detection sensitivity for latent faults of distribution network equipment.

The above-described embodiments of the present application do not limit the protection scope of the present application.

Claims (6)

1. A method for evaluating latent faults of power distribution network equipment is characterized by comprising the following steps:

s100, selecting one phase of A, B, C three-phase lines in the power distribution network system as an operation phase x, the other two phases as phases y and z to be tested, and the operation phase voltage corresponding to the operation phase x is U_xThe phase voltage to be measured corresponding to the phase y and the phase z to be measured is U_y、U_zWherein x, y, z is A, B or C;

s200, obtaining a starting setting value delta U₀Reducing phase voltage of an operating phase to zero, simulating an operation state when a single-phase earth fault occurs in a power distribution network system, measuring voltage variation of a neutral point before and after the fault, and taking the voltage variation of the neutral point as a starting setting value delta U of an partial discharge detection module₀；

S300, operating phase voltage U_xPerforming multiple voltage reduction operations, and measuring voltage variation U of neutral point during each voltage reduction operation_iI is the number of times of pressure reduction, i is 1, 2 … …;

s400, sequentially judging the variation U of the neutral point voltage in each voltage drop operation_iWhether or not equal to the starting setting value delta U₀When U is formed_iEqual to starting setting value delta U₀Measuring the partial discharge of the power distribution network equipment on the phases y and z to be measured;

s500, judging whether the insulation of the power distribution network equipment on the phases y and z to be tested has a latent fault risk or not according to the local discharge amount of the power distribution network equipment on the phases y and z to be tested, and if the latent fault risk exists, calibrating the safety state of the power distribution network equipment on the phases y and z to be tested as the latent fault risk exists;

s600, changing the operation phase, and repeating the steps S200-S400 until A, B, C three phases are all used as one operation phase;

s700, whether the safety state of the power distribution network equipment on the three-phase line is calibrated at least twice to be a latent fault risk or not is judged A, B, C, and if the safety state of the power distribution network equipment on the A, B or the C three-phase line is calibrated at least twice to be a latent fault risk, the situation that the power distribution network equipment on the A, B or the C three-phase line has a latent fault is judged.

2. The method for evaluating the latent fault of the power distribution network equipment according to claim 1, wherein S200, a starting setting value delta U is obtained₀Specifically, the method comprises the following steps of,

s210, operating a control switch to enable an x-phase voltage corresponding to an operating phase x on the phase power supply generator to be connected to a neutral point;

s220, adjusting the output voltage of the phase power supply generator to make the phase voltage U operate_xIs reduced to U'_xCalculating the first neutral point voltage as U₀₁＝U_x-U′_x；

S230, secondarily regulating the phase power supply generator to operate the phase voltage U_xReduced to U_xCalculating the second neutral point voltage as U (0V)₀₂＝U_x-U″_x；

S240, according to the first neutral point voltage U₀₁And the second neutral point voltage U₀₂Calculating a starting setting value delta U₀Wherein, Δ U₀＝U₀₁-U₀₂＝U″_x-U′_x。

3. An evaluation system for latent faults of power distribution network devices, for a power distribution network system comprising A, B, C three-phase lines, characterized by comprising a phase supply generator (1), the phase supply generator (1) being intended for connection to a neutral point of the power distribution network system, the phase supply generator (1) comprising A, B, C three-phase supply lines, A, B, C three-phase supply lines each generating a U voltage to the power distribution network system_A、U_BAnd U_CVoltages with opposite phases and same amplitude;

the control switch (2) is arranged on the connection between the phase power supply generator (1) and the neutral point of the power distribution network system, and the control switch (2) is used for controlling A, B, C three-phase power supply of the phase power supply generator to correspondingly control A, B, C three-phase line voltage on the power distribution network system;

the evaluation system for the latent fault of the power distribution network equipment further comprises a fault evaluation device and a plurality of detection devices which are connected with the evaluation device, wherein the detection devices comprise three-phase coupling capacitors (3), setting devices (6) and partial discharge monitoring devices (4) which are connected with the three-phase coupling capacitors (3),

the three-phase coupling capacitor (3) is used for coupling a partial discharge signal of the power distribution network equipment with a voltage value of the power distribution network system;

the setting device (6) includes:

the voltage acquisition module is used for acquiring the voltage value of the power distribution network system in real time;

a setting calculation module for calculating a starting setting value delta U according to the three-phase voltage of the system₀；

A setting judgment module for judging the variation U of the neutral point voltage_iWhether or not equal to the starting setting value delta U₀；

The partial discharge starting module is used for sending a starting instruction to the partial discharge monitoring device;

the partial discharge monitoring device (4) comprises:

the partial discharge detection module is used for acquiring partial discharge signals of the power distribution network equipment;

the data transmission module is used for transmitting the partial discharge signal to the state evaluation device;

the system for evaluating the insulation latent fault of the power distribution network equipment further comprises a plurality of groups of detection devices,

the fault evaluation device (5) specifically comprises:

the communication module is used for receiving the partial discharge signal;

the state calibration module is used for calibrating A, B or the safety state of the power distribution network equipment on the C three-phase line according to the partial discharge signal;

and the fault determination module is used for determining A, B whether the power distribution network equipment on the C three-phase line has a latent fault according to the safety state of the power distribution network equipment.

4. The system for evaluating the latent fault of the power distribution network equipment according to claim 3, wherein one end of the three-phase coupling capacitor (3) is installed on the high-voltage side of the power distribution network equipment, and the other end of the three-phase coupling capacitor is connected with the partial discharge monitoring device.

5. The system for assessing the latent fault of the power distribution network equipment according to claim 3, characterized in that the partial discharge monitoring device (4) is connected to the three-phase coupling capacitor (3) at one end and to ground at the other end.

6. The system for assessing latent faults in power distribution network equipment according to claim 3, wherein the distribution of the plurality of detection devices is: and the detection devices are arranged on the lines of the power distribution network system at preset intervals.

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