Ground fault detection and isolation method and system

Abstract

The invention belongs to the technical field of power distribution networks, and provides a ground fault detection and isolation method and system. The method comprises the following steps that: when a fault occurs in a distribution line, FTUs (Feeder Terminal Units) of each monitoring group identify and locate a grounding fault section according to the criteria that the zero-sequence current is increased after the fault occurs and the phase difference of the zero-sequence current before and after a fault point is 180 degrees; when the nearest upstream switch of the ground fault section meets the ground fault isolation condition, the node switch is matched with the FTU to control the node switch to trip, so that the downstream line section is powered off, and the ground fault is isolated out of the power supply line; when the reclosing delay time of the FTU matched with the nearest upstream switch of the fault section is up, the FTU controls the corresponding node switch to reclose, the type of the ground fault is judged according to whether the ground fault is detected again within the reclosing confirmation time, and then the corresponding isolation processing operation is matched according to the type of the ground fault.

Description

Technical Field

[0001] The present invention belongs to the technical field of power distribution network, and in particular relates to a ground fault detection and isolation method and system. Background Art

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

[0003] Although the fault current of a single-phase grounding fault is not large, there will be a large step voltage at the grounding point. If people approach the grounding point or touch the grounding equipment, personal injury will occur, which poses a major hidden danger. The current grounding fault detection and isolation processing technology for primary and secondary fusion pole-mounted circuit breakers mainly adopts centralized feeder automation technology and local feeder automation technology. Among them, the centralized feeder automation technology uses the optical fiber communication network to quickly send the fault distribution terminal information and data to the distribution master station through the working cooperation between the distribution master station and the distribution terminal equipment. The distribution master station will analyze and compare the received fault information and data to realize the distribution line fault location, fault isolation and restoration of power supply to non-fault areas. Feeder automation processing mode. The local feeder automation technology mainly includes voltage-time type, voltage-current time type, and adaptive feeder automation mode to realize fault location and fault isolation of distribution lines.

[0004] However, the existing feeder automation technology still has the following disadvantages:

[0005] (1) Centralized feeder automation has the risk of network congestion. The information and data of all distribution terminal equipment on the distribution line are sent to the distribution master station for data processing and fault decision-making. This leads to low fault handling efficiency and data transmission congestion, which results in fault handling failure. Centralized feeder automation has high requirements for communication reliability and relies more on optical fiber communication. However, laying optical fiber is difficult and costly. Therefore, centralized feeder automation is mainly used in urban central areas with high load density and high requirements for power supply reliability.

[0006] (2) Traditional local feeder automation has problems such as difficulty in setting protection settings, prone to over-tripping, poor fault location accuracy and fault handling accuracy, multiple reclosing to isolate faults has a great impact on the power grid, power outages or multiple power outages in non-fault areas, excessively large power outage areas, and long fault isolation and fault handling times.

[0007] To sum up, in the field of distribution network, distribution line FTU (Feeder Terminal Unit, distribution switch monitoring terminal), DTU (Data Transfer unit, a wireless terminal device specially used to convert serial port data into IP data or convert IP data into serial port data for transmission through a wireless communication network), primary and secondary fusion pole-mounted circuit breakers, primary and secondary fusion pole ring network boxes and other equipment are complicated, with few collection points, single data sources, different data collection times and new energy access to the distribution network leading to complex power supply, resulting in low single-phase grounding fault detection rate in the distribution network, poor fault isolation effect and long fault handling time. Summary of the invention

[0008] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a ground fault detection and isolation method and system, which can improve the accuracy of judging weak characteristic ground faults and shorten the processing time of ground faults.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A first aspect of the present invention provides a ground fault detection and isolation method.

[0011] A ground fault detection and isolation method, comprising:

[0012] According to the distribution lines, the direction of the power supply current and the connection relationship between the node switches, the upstream and downstream relationship of the node switch power supply is determined, and the node switches on the distribution lines are divided into several monitoring groups;

[0013] When a distribution line fails, the FTUs of each monitoring group identify and locate the ground fault section based on the criterion that the zero-sequence current increases after the fault occurs and the phase difference between the zero-sequence current before and after the fault point is 180°;

[0014] When the nearest upstream switch in the ground fault section meets the ground fault isolation conditions, the FTU supporting the node switch controls its tripping to cut off the power supply to the downstream line section, isolating the ground fault from the power supply line;

[0015] When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section expires, the FTU controls the corresponding node switch to reclose, and determines the type of grounding fault based on whether the grounding fault is detected again within the reclosing confirmation time, and then matches the corresponding isolation processing operation based on the type of grounding fault.

[0016] As an implementation method, each monitoring group includes adjacent switches and FTUs, and the FTU is used to monitor the downstream section information of its corresponding node switch and the information of its connected node switches.

[0017] As an implementation method, when a certain FTU detects a ground fault signal, the FTU obtains the ground fault moment fault signal from the FTU matching the node switch in the related monitoring group, and sends its own fault signal to the FTU matching the node switch in the related monitoring group.

[0018] As an implementation method, when the reclosing delay time of the FTU supporting the nearest upstream switch of the fault section expires, and the ground fault is not detected again within the reclosing confirmation time, it is a transient ground fault. The FTU sends the relevant information to the FTU in the related monitoring group and reports the transient ground fault information to the distribution master station, otherwise it is a permanent ground fault.

[0019] As an implementation method, when it is a permanent ground fault, the FTU supporting the upstream switch of the fault section fails to control the reclosing of the switch, the FTU controls the switch to trip again, the FTU locks the closing, and sends the node switch fault signal and processing information to the node switch supporting FTU in the related monitoring group.

[0020] As an implementation method, the FTU supporting the node switch in the relevant monitoring group of the faulty section controls the tripping, locking and closing of the corresponding node switch according to the line power supply direction and the switch position relationship, or controls the closing of the corresponding node switch to supply power to the non-faulty section line, and reports the node switch fault signal and processing information to the distribution master station.

[0021] As an implementation method, after the fault is eliminated, the relevant node switches are closed or tripped by controlling the power distribution master station or locally through the FTU to restore the line to a normal power supply network structure and power supply status.

[0022] As an implementation method, the FTU of each monitoring group uses the Beidou clock signal wide area synchronization method to synchronously collect signals.

[0023] As an implementation method, the Beidou clock signal wide area synchronization method is:

[0024] Using multiple second pulses as the time reference, sample m second pulses. At this time, the crystal oscillator output frequency f real for:

[0025]

[0026] Where P is the frequency multiplication factor; W1 and W2 are the counter count values ​​corresponding to adjacent second pulses; G m is the number of timer overflow restarts; Y is the FTU telemetry acquisition channel.

[0027] A second aspect of the present invention provides a ground fault detection and isolation system.

[0028] Ground fault detection and isolation system, including:

[0029] Node switches of distribution lines and their matching FTUs;

[0030] The node switches of the distribution line are divided into several monitoring groups according to their upstream and downstream power supply relationships; each monitoring group includes adjacent switches and FTUs, and the FTU is used to monitor the downstream section information of its corresponding node switch and the information of its connected node switches;

[0031] When a distribution line fails, the FTU of each monitoring group is used to identify and locate the ground fault section based on the criterion that the zero-sequence current increases after the fault occurs and the phase difference between the zero-sequence current before and after the fault point is 180°;

[0032] When the nearest upstream switch in the ground fault section meets the ground fault isolation conditions, the FTU supporting the node switch is used to control its tripping, so that the downstream line section is de-energized and the ground fault is isolated from the power supply line;

[0033] When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section is reached, the FTU is used to control the reclosing of the corresponding node switch. The type of grounding fault is determined based on whether the grounding fault is detected again within the reclosing confirmation time, and the corresponding isolation processing operation is matched according to the type of grounding fault.

[0034] The beneficial effects of the present invention are:

[0035] The present invention innovatively proposes a grounding fault detection and isolation technology for a primary and secondary integrated pole-mounted circuit breaker. When a grounding fault occurs, the FTUs supporting the upstream and downstream switches in the fault area trigger fault information collection and transmit the collected data to the FTUs supporting the adjacent switches. The relevant FTUs compare their own collected data with the data collected by their adjacent switches at the same time, and use the principle of multi-point zero-sequence current waveform similarity to accurately locate the grounding fault area. The FTUs supporting the switches of the nearest upstream and downstream nodes in the grounding fault area control the switch to trip, directly isolating the fault area, greatly shortening the grounding fault positioning and fault isolation time, solving the current problems of low single-phase grounding fault detection rate, poor fault isolation effect and long fault processing time in the distribution network, and realizing self-healing of grounding faults in distribution lines in seconds; at the same time, it effectively avoids the phenomenon of tripping of over-level switches, power outages in non-fault areas and multiple reclosing of multi-level switches to impact the power grid.

[0036] The present invention innovatively proposes a multi-terminal (FTU) fault data analysis technology, obtains accurate time synchronization through the Beidou satellite navigation system, utilizes the accurate time synchronization of FTU, accurately synchronizes the data sampling of different switches, compares the data of the previous and next switches at the same time, accurately determines the grounding fault area, and improves the accuracy of weak characteristic grounding fault analysis.

[0037] The present invention innovatively proposes a ground fault isolation technology for a primary-secondary fused pole-mounted circuit breaker. The advantages of additional aspects of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0039] Figure 1 is a flow chart of a ground fault detection and isolation method according to an embodiment of the present invention;

[0040] Figure 2 Schematic diagram of a power distribution network according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0043] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0044] like Figure 1 As shown, an embodiment of the present invention provides a ground fault detection and isolation method, including:

[0045] Step 1: According to the distribution lines, the direction of the power supply current and the connection relationship between each node switch, determine the upstream and downstream relationship of the node switch power supply, and divide the node switches on the distribution line into several monitoring groups;

[0046] Step 2: When a distribution line fault occurs, the FTU of each monitoring group identifies and locates the ground fault section based on the criterion that the zero-sequence current increases after the fault occurs and the phase difference between the zero-sequence current before and after the fault point is 180°.

[0047] In this embodiment, the FTU of each monitoring group uses the Beidou clock signal wide area synchronization method to synchronize the acquisition signal. Among them, the Beidou clock signal wide area synchronization method is:

[0048] Using multiple second pulses as the time reference, sample m second pulses. At this time, the crystal oscillator output frequency f real for:

[0049]

[0050] Where P is the frequency multiplication factor; W1 and W2 are the counter count values ​​corresponding to adjacent second pulses; G m is the number of timer overflow restarts; Y is the FTU telemetry acquisition channel.

[0051] Step 3: When the nearest upstream switch in the ground fault section meets the ground fault isolation condition, the FTU supporting the node switch controls its tripping to cut off the power supply to the downstream line section, isolating the ground fault from the power supply line;

[0052] Step 4: When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section expires, the FTU controls the corresponding node switch to reclose, and determines the type of the grounding fault based on whether the grounding fault is detected again within the reclosing confirmation time, and then matches the corresponding isolation processing operation based on the type of grounding fault.

[0053] In this embodiment, each monitoring group includes adjacent switches and FTUs, and the FTU is used to monitor the downstream section information of its corresponding node switch and the information of its connected node switches.

[0054] When a certain FTU detects a ground fault signal, it obtains the ground fault moment fault signal from the FTU matching the node switch in the related monitoring group through the FTU, and sends its own fault signal to the FTU matching the node switch in the related monitoring group.

[0055] When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section expires, and the ground fault is not detected again within the reclosing confirmation time, it is a transient ground fault. The FTU sends the relevant information to the FTU in the related monitoring group and reports the transient ground fault information to the distribution master station, otherwise it is a permanent ground fault.

[0056] When it is a permanent ground fault, the FTU supporting the nearest upstream switch in the fault section fails to control the switch to reclose, and the FTU controls the switch to trip again. The FTU locks and closes, and sends the node switch fault signal and processing information to the node switch supporting FTU in the related monitoring group.

[0057] The FTU supporting the node switch in the relevant monitoring group of the fault section controls the tripping, locking and closing of the corresponding node switch according to the power supply direction of the line and the position relationship of the switch, or controls the corresponding node switch to close to supply power to the non-fault section line, and reports the node switch fault signal and processing information to the distribution master station;

[0058] When the fault is eliminated, the relevant node switches are closed or tripped through the distribution master station or locally through the FTU to restore the line to the normal power supply network structure and power supply status.

[0059] The following is combined with Figure 2 To illustrate the specific implementation process of the embodiment of the present invention:

[0060] Assume that a ground fault occurs between FD2 and FD3, and it is a high-resistance ground with a weak characteristic small current signal;

[0061] When a ground fault occurs, the section switches FD1, FD2, FD3 and the boundary switch FJ3 detect the ground fault signal (zero-sequence voltage, zero-sequence current signal, and abnormal fluctuations of line voltage or phase voltage and phase current signal), and trigger the ground fault analysis, fault location and fault handling functions;

[0062] Among them, the criteria for ground fault analysis are:

[0063] The FTU of the monitoring group receives the data that the zero-sequence current increases after the fault occurs and the phase difference between the zero-sequence current before and after the fault point is 180°.

[0064] When a fault occurs, the node switch will trigger fault information collection, receive fault data from multiple adjacent switches, and compare the waveform of zero-sequence current according to the fault data analysis algorithm to accurately identify and locate the fault area. For example, n+1 points are compared one by one. When the value changes from negative to positive and the nth point is less than zero and the n+1th point is greater than zero, the comparison is stopped and the n value at this time is recorded. Because there is a time difference ΔT in the transmission of adjacent node data, according to the formula:

[0065] Among them, θ represents the angular velocity (i.e., phase difference) corresponding to the time difference of data transmission between adjacent nodes;

[0066] When n points are less than zero and the n+1th point is greater than zero, we can get:

[0067]

[0068] If Δt = 2ms, substitute into the above formula to get:

[0069]

[0070] Neighboring node n 1 and n2 The phase difference is θ 12 :

[0071]

[0072] At the same time, FD2 actively obtains the data of FD1, FD3, FD4 and FZ2, and compares and analyzes the data with its own data. FD2 finds that its own zero-sequence current waveform is quite different from the zero-sequence current waveform (amplitude and phase) of FD3, FD4 and FZ2 at the same time. FD2 finds that its own zero-sequence current waveform is slightly different from the zero-sequence current waveform (amplitude and phase) of FD1 at the same time. FD2 determines that the fault point is downstream; FD3 actively obtains the data of FD2, FZ2, FJ3 and LL1, and compares and analyzes the data with its own data. FD3 finds that its own zero-sequence current waveform is quite different from the zero-sequence current waveform (amplitude and phase) of FD2 and FZ2 at the same time. FD3 finds that its own zero-sequence current waveform is slightly different from the zero-sequence current waveform (amplitude and phase) of FJ3 at the same time. FD3 determines that the fault point is upstream ; FD1 finds that its own zero-sequence current waveform is slightly different from FD2 and significantly different from FD4 at the same time, and FD1 determines that the fault point is not downstream of its area; FZ2 finds that its own zero-sequence current waveform is significantly different from FD2 and FD3 and slightly different from FJ2 at the same time, and the fault point of FZ2 is not in its branch area or in its upstream area; FJ3 finds that its own zero-sequence current waveform is slightly different from FD3 at the same time, and FJ3 determines that the fault point is upstream and not in the upstream and downstream areas connected to it; FD1~FD3, FZ2 and FJ3 exchange information and perform data analysis through their own collected data and the collected data of adjacent switches. Finally, FD2, FD3 and FZ2 can locate the fault point in the area between FD2, FD3 and FZ2, and accurately locate the fault point in the area of ​​the power supply line where FD2 and FD3 are located.

[0073] If it is an instantaneous ground fault (the fault occurs for a short time), FD2 trips, and after the reclosing delay time is up, FD2 recloses. FD2 actively obtains the data collected by FD1, FD3, FD4, and FZ2 at the same time after the power supply is restored. The zero-sequence current signal and waveform of FD2 itself at the same time are slightly different from their zero-sequence current signals and waveforms. After the reclosing confirmation time is up, FD2 recloses successfully. FD1, FD3, FD4, FZ2, and FJ3 do not detect fault information within the FD2 call confirmation time. The contact switch LL1 restores the call within the single-side power loss confirmation time to maintain its switch state. Finally, the location and processing of this instantaneous ground fault are completed. At the same time, FD2 sends the fault information and its action information to the server via optical fiber or wireless form, and FD1, FD3, FZ2, FJ2, and FJ3 send the fault information to the server via optical fiber or wireless form.

[0074] If it is a permanent ground fault, after FD2 is reclosed, the section switches FD1, FD2, FD3 and the boundary switch FJ3 will immediately trigger and detect the ground fault signal. FD1~FD3, FZ2 and FJ3 will exchange information and analyze data collected by their own data with those collected by adjacent switches. FD2, FD3 and FZ2 can determine that the permanent ground fault point is in the area between FD2, FD3 and FZ2, and accurately locate the permanent fault point in the area of ​​the power supply line where FD2 and FD3 are located.

[0075] Because it is a permanent ground fault, FD2 detects the ground fault information again within the reclosing confirmation time and determines that a permanent ground fault occurs in its downstream area. FD2 reclosing fails, FD2 trips and locks the switch, and FD3 and FZ2 immediately trip and lock the switch when power is lost again. At the same time, FD2, FD3 and FZ2 send the fault information and switch action information to the server via optical fiber or wireless form.

[0076] Because it is a permanent ground fault, after FD2 recloses, the section switch FD1 detects the ground fault signal again. FD1 actively obtains the data of FD2 and FD4 again and compares and analyzes it with its own data. FD1 finds that its own zero-sequence current waveform is slightly different from the zero-sequence current waveform of FD2 (amplitude and phase) at the same time. FD1 finds that its own zero-sequence current waveform is significantly different from the zero-sequence current waveform of FD4 (amplitude and phase) at the same time. It is judged that the permanent ground fault point is not in the adjacent area of ​​FD1, and FD1 does not trip. At the same time, FD1 sends the fault information to the server via optical fiber or wireless form;

[0077] Because it is a permanent ground fault, during the period of FD2 tripping, reclosing and tripping, the contact switch LL1 detects that the line near FD3 has a "power failure-short-time power restoration-power failure" phenomenon. When the LL1 single-side voltage loss delay timer expires, LL1 closes and restores power supply to FD3 and LL1, FJ3 non-fault areas. At the same time, LL1 sends its action information to the server via optical fiber or wireless form;

[0078] Finally, the areas between FD2, FD3, and FZ2 are isolated, and other non-fault areas are powered normally.

[0079] When the permanent grounding fault point between FD2 and FD3 is eliminated, the power distribution master station remotely controls FD2, FD3, and FZ2 to close, and remotely controls LL1 to open, so as to restore the line power supply grid structure to the state before the fault.

[0080] In another embodiment, a ground fault detection and isolation system is provided, comprising:

[0081] Node switches of distribution lines and their matching FTUs;

[0082] The node switches of the distribution line are divided into several monitoring groups according to their upstream and downstream power supply relationships; each monitoring group includes adjacent switches and FTUs, and the FTU is used to monitor the downstream section information of its corresponding node switch and the information of its connected node switches;

[0083] When a distribution line fails, the FTU of each monitoring group is used to identify and locate the ground fault section based on the criterion that the zero-sequence current increases after the fault occurs and the phase difference between the zero-sequence current before and after the fault point is 180°;

[0084] When the nearest upstream switch in the ground fault section meets the ground fault isolation conditions, the FTU supporting the node switch is used to control its tripping, so that the downstream line section is de-energized and the ground fault is isolated from the power supply line;

[0085] When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section is reached, the FTU is used to control the reclosing of the corresponding node switch. The type of grounding fault is determined based on whether the grounding fault is detected again within the reclosing confirmation time, and the corresponding isolation processing operation is matched according to the type of grounding fault.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A ground fault detection and isolation method, characterized in that: include: According to the distribution lines, the direction of the power supply current and the connection relationship between the node switches, the upstream and downstream relationship of the node switch power supply is determined, and the node switches on the distribution lines are divided into several monitoring groups; When a distribution line fails, the FTUs of each monitoring group identify and locate the ground fault section based on the criterion that the zero-sequence current increases after the fault occurs and the phase difference between the zero-sequence current before and after the fault point is 180°; When the nearest upstream switch in the ground fault section meets the ground fault isolation conditions, the FTU supporting the node switch controls its tripping to cut off the power supply to the downstream line section, isolating the ground fault from the power supply line; When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section expires, the FTU controls the corresponding node switch to reclose, and determines the type of grounding fault based on whether the grounding fault is detected again within the reclosing confirmation time, and then matches the corresponding isolation processing operation based on the type of grounding fault.

2. The ground fault detection and isolation method according to claim 1, characterized in that: Each monitoring group includes adjacent switches and FTUs. The FTU is used to monitor the downstream section information of its corresponding node switch and the information of its connected node switches.

3. The ground fault detection and isolation method according to claim 1, characterized in that: When a certain FTU detects a ground fault signal, it obtains the ground fault moment fault signal from the FTU matching the node switch in the related monitoring group through the FTU, and sends its own fault signal to the FTU matching the node switch in the related monitoring group.

4. The ground fault detection and isolation method according to claim 1, characterized in that: When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section expires, and the ground fault is not detected again within the reclosing confirmation time, it is a transient ground fault. The FTU sends the relevant information to the FTU in the related monitoring group and reports the transient ground fault information to the distribution master station, otherwise it is a permanent ground fault.

5. The ground fault detection and isolation method according to claim 4, characterized in that: When it is a permanent ground fault, the FTU supporting the nearest upstream switch in the fault section fails to control the switch to reclose, and the FTU controls the switch to trip again. The FTU locks and closes, and sends the node switch fault signal and processing information to the node switch supporting FTU in the related monitoring group.

6. The ground fault detection and isolation method according to claim 1, characterized in that: The FTU supporting the node switch in the relevant monitoring group of the faulty section controls the tripping, locking and closing of the corresponding node switch according to the line power supply direction and switch position relationship, or controls the closing of the corresponding node switch to supply power to the non-faulty section line, and reports the node switch fault signal and processing information to the distribution master station.

7. The ground fault detection and isolation method according to claim 1, characterized in that: When the fault is eliminated, the relevant node switches are closed or tripped through the distribution master station or locally through the FTU to restore the line to the normal power supply network structure and power supply status.

8. The ground fault detection and isolation method according to claim 1, characterized in that: The FTU of each monitoring group uses the Beidou clock signal wide-area synchronization method to synchronously collect signals.

9. The ground fault detection and isolation method according to claim 8, characterized in that: The Beidou clock signal wide-area synchronization method is: Using multiple second pulses as the time reference, sample m second pulses. At this time, the crystal oscillator output frequency f real for: Where P is the frequency multiplication factor; W1 and W2 are the counter count values ​​corresponding to adjacent second pulses; G m is the number of timer overflow restarts; Y is the FTU telemetry acquisition channel.

10. Ground fault detection and isolation system, characterized in that, include: Node switches of distribution lines and their matching FTUs; The node switches of the distribution line are divided into several monitoring groups according to their upstream and downstream power supply relationships; each monitoring group includes adjacent switches and FTUs, and the FTU is used to monitor the downstream section information of its corresponding node switch and the information of its connected node switches; When a distribution line fails, the FTU of each monitoring group is used to identify and locate the ground fault section based on the criterion that the zero-sequence current increases after the fault occurs and the phase difference between the zero-sequence current before and after the fault point is 180°; When the nearest upstream switch in the ground fault section meets the ground fault isolation conditions, the FTU supporting the node switch is used to control its tripping, so that the downstream line section is de-energized and the ground fault is isolated from the power supply line; When the reclosing delay time of the FTU supporting the nearest upstream switch in the fault section is reached, the FTU is used to control the reclosing of the corresponding node switch. The type of grounding fault is determined based on whether the grounding fault is detected again within the reclosing confirmation time, and the corresponding isolation processing operation is matched according to the type of grounding fault.

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