Active search method and system for isolating and self-repairing power grid faults.

Abstract

Each switch in the power distribution network is equipped with a protection device with a time-delayed power frequency current protection function and a time-delayed active search current protection function. The power frequency current protection and the active search current protection function coordinate with each other in a time-delayed manner in the forward and reverse directions to isolate a power distribution network fault. The protection device has a fault self-repair function and detects voltage changes in the active search signal to determine whether the fault has been isolated. If the fault has been isolated, the protection device closes the power supply connection switch and resumes power supply to the healthy section. The search signal is actively injected from an islanding distributed power source in the power distribution network. By utilizing the flexibility and controllability of distributed power sources in the power system, the faulted section can be accurately isolated on the spot without the need for communications, and power supply to the healthy section can be quickly resumed. This reduces the scope and duration of the power outage caused by the fault, thereby improving the reliability of the power supply.

Description

[Technical Field]

[0001] The present invention belongs to the technical field of protective relays for power systems, and more particularly to a method and system for the isolation and self-repair of active search-type power distribution network faults. [Background technology]

[0002] China's power grid is transitioning from a traditional passive grid to one that includes a high proportion of distributed power sources, and handling failures in this grid presents new challenges.

[0003] The introduction of a high proportion of distributed power sources into the power grid alters the characteristics of the grid's original single-source and radial structure. Power flow in each branch line of the distribution grid no longer flows in one direction, directly changing the direction and magnitude of short-circuit currents in the power system and significantly impacting protection configurations that primarily rely on commercial frequency overcurrent protection. The injection or shunting effect of distributed power sources may increase or decrease the fault current flowing through protective devices, potentially changing the protection range and sensitivity of the devices. If the overcurrent protection setting is increased, the commercial frequency current supplied from the distributed power sources may be limited (less than 1.2 times the rated current), potentially preventing the protective devices on the distributed power source side from operating. Conversely, if the overcurrent protection setting is decreased, the distributed power sources supply injected current, potentially causing the protective devices on the power grid side to malfunction. Furthermore, feeder automation systems identify fault sections by detecting overcurrent signals, and with the large-scale introduction of distributed power sources, overcurrent signals may be detected on both sides of the fault point, rendering conventional methods ineffective. [Overview of the project] [Problems that the invention aims to solve]

[0004] The new characteristics of the power grid present challenges in fault handling, but also offer new opportunities for advancements in power grid protection relays. A key difference between new and conventional power grids is that a large number of distributed power sources, energy storage facilities, and other equipment are connected to the grid through converters (power electronics equipment), and these converters themselves possess high controllability. By designing additional control strategies within the allowable current transmission capacity of the power electronics equipment, the equipment can inject characteristic signals that are infrequent or absent in normal fault conditions during a fault. Protection devices can recognize these characteristic signals, enabling fault identification and pinpointing, accurate fault isolation, and rapid recovery. Based on solving the new problems brought about by the introduction of distributed power sources, this effectively addresses long-standing challenges in power grid fault handling technology, transforming unfavorable conditions into favorable ones.

[0005] Focusing on the problems that arise in dealing with faults due to the large-scale introduction of distributed power sources into the power distribution network, the present invention proposes an active search-type method for separating and self-repairing power distribution network faults, which achieves power distribution network fault isolation and restoration under conditions where communication is not required by having the distributed power sources actively inject search signals, thereby improving the reliability of power supply. [Means for solving the problem]

[0006] To achieve the above technical objectives and produce the above technical effects, the present invention employs the following technical means.

[0007] In a first embodiment, the active search type power distribution network fault isolation and self-repair method provided by the present invention is configured such that each switch in the power distribution network is fitted with a protective device equipped with a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and the active search current protection work in stepwise coordination with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device is equipped with a fault self-repair function and determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the power supply communication switch and resumes power supply to the healthy section, and the fault response method has the following configuration. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, a protective device in the communication switch detects a change in the voltage of the active search signal and determines whether the fault has been isolated based on the change in the voltage of the active search signal. If it is determined that the fault has been isolated, the switch is closed after a delay of t3 to resume power supply to the healthy section.

[0008] As a stepwise coordination method based on the time difference between the fixed-time commercial frequency current protection and the fixed-time active search current protection, the commercial frequency current protection coordinates stepwise from the forward direction (flow from the busbar to the power line), meaning that the closer the protection device is to the power supply, the longer the operating time. The active search current protection coordinates stepwise from the reverse direction (flow from the power line to the busbar), meaning that the closer the protection device is to the power supply, the shorter the operating time.

[0009] The search signal actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, or a pulsed square wave.

[0010] The start time and duration of injecting the search signal from the distributed power supply can both be set. The start time is the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration is set to a set value.

[0011] The time at which the search signal is injected from the distributed power supply is the set initial phase angle φ set Determined by, φset It is at an angle of 0 to 360°, usually set to 0°.

[0012] The procedure for determining whether a fault is isolated based on the change in the voltage of the active exploration signal is The protection device includes collecting the active exploration voltage signal, calculating its symmetry, and determining that a fault is isolated when the active exploration voltage changes from asymmetric to symmetric.

[0013] The conditions for voltage asymmetry are as follows.

Number

[0014] The conditions for voltage symmetry are as follows.

Number

[0015] In the second aspect, the active exploration type distribution network fault isolation and self-healing method provided by the present invention respectively installs protection devices with definite-time commercial-frequency current protection and definite-time active exploration current protection functions on each switch of the distribution network. The commercial-frequency current protection and the active exploration current protection respectively cooperate step by step with a time difference from the forward and reverse directions to complete the isolation of the distribution network fault. The protection device has a fault self-healing function, detects the change in the voltage of the active exploration signal, determines whether a fault is isolated, and when a fault is isolated, closes the power connection switch to resume power supply to the healthy section. The treatment method during a fault has the following configuration. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the islanding distributed power supply actively injects the search signal S2. (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section.

[0016] As a stepwise coordination method based on the time difference between the fixed-time commercial frequency current protection and the fixed-time active search current protection, the commercial frequency current protection coordinates stepwise from the forward direction (flow from the busbar to the power line), meaning that the closer the protection device is to the power supply, the longer the operating time. The active search current protection coordinates stepwise from the reverse direction (flow from the power line to the busbar), meaning that the closer the protection device is to the power supply, the shorter the operating time.

[0017] The search signal actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, or a pulsed square wave. The start time and duration of injecting the search signal from the distributed power supply can both be set. The start time is the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration is set to a set value.

[0018] The time at which the search signal is injected from the distributed power supply is the set initial phase angle φ set Determined by, φ setThis ranges from 0 to 360° and is usually set to 0°.

[0019] The search signals S1 and S2 injected from the distributed power supply have different waveforms.

[0020] In the first and second embodiments, preferred technical means include the search signal injected from the distributed power supply being intermittent, i.e., injected over a certain time Tz, then paused for a certain time Tn, and so on, with the cycle repeating.

[0021] In this case, the operating conditions for the active search current protection have the following configuration. (1) The active search signal is detected, and the signal current is greater than the current threshold set for protection. (2) The detected active search signal satisfies the discontinuous characteristics, (3) The duration of the active search signal is greater than the protected delay threshold. (4) The ratio of the active search current to the commercial frequency current is greater than the set threshold (usually 0.6).

[0022] In a third embodiment, an active search type power distribution network fault isolation and self-repair system is provided, wherein each switch in the power distribution network is fitted with a protective device that has a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and the active search current protection work in stepwise coordination with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the power supply communication switch and resumes power supply to the healthy section, and the fault response method has the following configuration. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, a protective device in the communication switch detects a change in the voltage of the active search signal and determines whether the fault has been isolated based on the change in the voltage of the active search signal. If it is determined that the fault has been isolated, the switch is closed after a delay of t3 to resume power supply to the healthy section.

[0023] In a fourth embodiment, an active search type power distribution network fault isolation and self-repair system is provided, wherein each switch in the power distribution network is equipped with a protective device that has a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and the active search current protection work in stepwise coordination with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the communication switch and resumes power supply to the healthy section, and the fault response method has the following configuration. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the islanding distributed power supply actively injects the search signal S2. (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section. [Effects of the Invention]

[0024] Compared to conventional technology, the advantageous effects of the present invention include: This invention proposes an active search-type method for the isolation and self-repair of power grid faults. It can transform the adverse effects of the introduction of distributed power sources on fault isolation into favorable conditions. This method eliminates the need for communication, accurately isolates the faulty section on the spot, rapidly restores power supply to healthy sections, reduces the extent of power outages, shortens downtime, and significantly improves the reliability of power supply. This method adapts to the evolving trend of large-scale distributed power source deployment and is useful in the construction of power systems.

[0025] To help you understand the contents of the present invention more clearly, specific embodiments will be described below with reference to the drawings. [Brief explanation of the drawing]

[0026] [Figure 1] This is a system configuration diagram of the present invention. [Figure 2] This is a flowchart showing the procedures to be taken in the event of a malfunction in the first embodiment. [Figure 3] This is a flowchart for handling a malfunction in the second embodiment. [Modes for carrying out the invention]

[0027] To make the object, technical means, and advantages of the present invention more apparent, the present invention will be described below with reference to embodiments. The specific embodiments described herein are used solely for the purpose of illustrating the present invention and are not intended to limit the scope of protection of the present invention.

[0028] The application principle of this invention will be described in detail below with reference to the drawings.

[0029] (First Embodiment) Embodiments of the present invention provide an active search type method for the isolation and self-repair of power distribution network faults, as shown in Figure 1, in which each switch in the power distribution network is fitted with a protective device, and the protective device detects an active search signal injected from a distributed power source to complete the isolation and self-repair of the power distribution network fault.

[0030] The protection device is equipped with fixed-time commercial frequency current protection and fixed-time active search current protection functions. The commercial frequency current protection and active search current protection functions work in a stepwise manner with a time difference from the forward and reverse directions, respectively, to complete the isolation of the power distribution network fault. The protection device is equipped with a fault self-repair function and determines whether the fault has been isolated by detecting a change in the voltage of the active search signal. If the fault has been isolated, it closes the power supply communication switch and resumes power supply to the healthy section. As shown in Figure 2, the specific procedure for handling a fault is as follows. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, a protective device in the communication switch detects a change in the voltage of the active search signal and determines whether the fault has been isolated based on the change in the voltage of the active search signal. If it is determined that the fault has been isolated, the switch is closed after a delay of t3 and power supply to the healthy section is restored.

[0031] As a stepwise coordination method based on the time difference between the fixed-time commercial frequency current protection and the fixed-time active search current protection, the commercial frequency current protection coordinates stepwise from the forward direction (flow from the busbar to the power line), meaning that the closer the protection device is to the power supply, the longer the operating time. The active search current protection coordinates stepwise from the reverse direction (flow from the power line to the busbar), meaning that the closer the protection device is to the power supply, the shorter the operating time.

[0032] The search signal S1 actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, and a pulsed square wave. The start time and duration of injecting the search signal from the distributed power supply can both be set. The start time is the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration is set to a set value.

[0033] The time at which the search signal is injected from the distributed power supply is the set initial phase angle φ set Determined by, φ set This ranges from 0 to 360° and is usually set to 0°.

[0034] In some embodiments, the procedure for determining whether a fault has been isolated based on a change in the voltage of an active search signal is as follows: The protection device includes collecting an active search voltage signal, calculating its symmetry, and determining that a fault has been isolated if the active search voltage changes from asymmetric to symmetric.

[0035] The conditions for voltage asymmetry are as follows:

number

[0036] The voltage symmetry conditions are as follows:

number

[0037] In some preferred technical means, the search signal injected from the distributed power supply is intermittent, i.e., injected over a certain time Tz, then paused for a certain time Tn, and such a cycle is repeated. In this case, the operating conditions for the active search current protection are that the following conditions are simultaneously met: (1) The active search signal is detected, and the signal current is greater than the current threshold set for protection. (2) The detected active search signal satisfies the discontinuous characteristics, (3) The duration of the active search signal is greater than the protected delay threshold.

[0038] (Second embodiment) Embodiments of the present invention provide an active search type method for the isolation and self-repair of power distribution network faults, as shown in Figure 1, in which each switch in the power distribution network is fitted with a protective device, and the protective device detects an active search signal injected from a distributed power source to complete the isolation and self-repair of the power distribution network fault.

[0039] The protection device is equipped with fixed-time commercial frequency current protection and fixed-time active search current protection functions. The commercial frequency current protection and active search current protection functions work in a stepwise manner with a time difference from forward and reverse directions, respectively, to complete the isolation of the power distribution network fault. The protection device is equipped with a fault self-repair function and determines whether the fault has been isolated by detecting a change in the voltage of the active search signal. If the fault has been isolated, it closes the power supply communication switch and resumes power supply to the healthy section. As shown in Figure 3, the specific procedure for handling a fault is as follows. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the islanding distributed power supply actively injects the search signal S2, (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section.

[0040] As a stepwise coordination method based on the time difference between the fixed-time commercial frequency current protection and the fixed-time active search current protection, the commercial frequency current protection coordinates stepwise from the forward direction (flow from the busbar to the power line), meaning that the closer the protection device is to the power supply, the longer the operating time. The active search current protection coordinates stepwise from the reverse direction (flow from the power line to the busbar), meaning that the closer the protection device is to the power supply, the shorter the operating time.

[0041] The search signal actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, or a pulsed square wave. The start time and duration of injecting the search signal from the distributed power supply can both be set. The start time is the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration is set to a set value.

[0042] The time at which the search signal is injected from the distributed power supply is the set initial phase angle φ set Determined by, φ setThis ranges from 0 to 360° and is usually set to 0°.

[0043] The search signals S1 and S2 injected from the distributed power supply have different waveforms.

[0044] In some preferred technical means, the search signal injected from the distributed power supply is intermittent, i.e., injected over a certain time Tz, then paused for a certain time Tn, and such a cycle is repeated. In this case, the operating conditions for the active search current protection are that the following conditions are simultaneously met: (1) The active search signal is detected, and the signal current is greater than the current threshold set for protection. (2) The detected active search signal satisfies the discontinuous characteristics, (3) The duration of the active search signal is greater than the protected delay threshold. (4) The ratio of the active search current to the commercial frequency current is greater than the set threshold (usually 0.6).

[0045] Specifically, as shown in Figure 2, according to the first embodiment, the differences between the embodiment of the present invention and the first embodiment are as follows: In the first embodiment, the active search signals injected from the distributed power sources before and after the separation of the power distribution network fault are the same, and the method by which the protection device determines that fault separation is complete is to detect that the voltage of the active search signal has changed from asymmetric to symmetric. In the first embodiment, the active search signals injected from the distributed power sources before and after the separation of the power distribution network fault are different, and the method by which the protection device determines that fault separation is complete is to detect that the voltage waveform of the active search signal has changed from one type to another.

[0046] (Third embodiment) An active search type power distribution network fault isolation and self-repair system is provided, in which each switch in the power distribution network is fitted with a protective device that has fixed-time commercial frequency current protection and fixed-time active search current protection functions, and the commercial frequency current protection and active search current protection work in stepwise coordination with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the power supply communication switch and resumes power supply to the healthy section, and the fault response method has the following configuration. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, a protective device in the communication switch detects a change in the voltage of the active search signal and determines whether the fault has been isolated based on the change in the voltage of the active search signal. If it is determined that the fault has been isolated, the switch is closed after a delay of t3 to resume power supply to the healthy section.

[0047] (Fourth embodiment) An active search type power distribution network fault isolation and self-repair system is provided, wherein each switch in the power distribution network is equipped with a protective device that has a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and active search current protection work in a stepwise manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the communication switch and resumes power supply to the healthy section, and the fault response method has the following configuration. (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and a protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) A protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and a protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the islanding distributed power supply actively injects the search signal S2. (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section.

[0048] As will be understood by those skilled in the art, embodiments of this application may be embodied as methods, systems, or computer program products. Thus, embodiments of this application may be entirely hardware, entirely software, or a combination of software and hardware aspects. Furthermore, embodiments of this application may be embodied in one or more computer-readable media (including, but not limited to, magnetic storage devices, CD-ROMs, optical storage devices, etc.) on which computer-readable program code is embodied.

[0049] This application will be described with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. Each flow and / or block in a flowchart and / or block diagram, as well as combinations of flows and / or blocks in a flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions may be provided to a general-purpose computer, a dedicated computer, or a processor of another programmable data processing device to produce a machine such that instructions executed via the processor of the computer or other programmable data processing device generate means for implementing the functions defined in the flows of a flowchart or the blocks or the blocks of a block diagram.

[0050] These computer program instructions may also be stored in a computer-readable medium that can instruct a computer, other programmable data processing device, or other device to function in a particular manner, such as to produce a product that includes instructions for implementing functions defined in a flowchart or a set of flows and / or a block or a set of blocks in a block diagram.

[0051] Computer program instructions may also be loaded onto a computer, other programmable data processing device, or other device to produce a computer implementation process, by causing a series of operational steps on the computer, other programmable device, or other device to be performed so as to provide a process for implementing a function defined in a flowchart or a set of flows and / or a block or a set of blocks in a block diagram.

[0052] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art will understand that the present invention is not limited to the embodiments described above. The above embodiments and specification illustrate the principles of the present invention, and without departing from the spirit and scope of the invention, the present invention may be modified and improved in various ways, and such modifications and improvements shall equally fall within the scope of the invention for which protection is claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

[0053] (Note) (Note 1) An active search type method for isolating and self-repairing power distribution network faults, wherein each switch in the power distribution network is equipped with a protection device having a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, the commercial frequency current protection and the active search current protection work in a stepwise coordinated manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, the protection device has a fault self-repair function and determines whether the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, the power supply communication switch is closed to resume power supply to the healthy section, and the procedure for handling a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds a set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault point detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault, and (4) After the fault is isolated, the protective device in the communication switch detects a change in the voltage of the active search signal, determines whether the fault has been isolated based on the change in the voltage of the active search signal, and if it is determined that the fault has been isolated, closes the switch after a delay of t3 and resumes power supply to the healthy section. An active search-type method for isolating and self-repairing power distribution network faults, characterized by including the following:

[0054] (Note 2) The method for gradual coordination between the fixed-time commercial frequency current protection and the fixed-time active search current protection, characterized in that the commercial frequency current protection is coordinated in stages starting from the forward direction, which is the direction in which current flows from the busbar to the power line, that is, the closer the protection device is to the power source, the longer the operating time becomes, and the active search current protection is coordinated in stages starting from the reverse direction, which is the direction in which current flows from the power line to the busbar, that is, the closer the protection device is to the power source, the shorter the operating time becomes, as described in Appendix 1, for the isolation and self-repair of an active search type power distribution network fault.

[0055] (Note 3) The search signal actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, or a pulsed square wave. And / or, the start time and duration of injecting the search signal from the distributed power supply can both be set, the start time being the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration being set to a set value. and / or, the time at which the search signal is injected from the distributed power supply is the set initial phase angle φ set Determined by, φ set It is an angle from 0 to 360°, and is usually set to 0°. The method for isolating and self-repairing a power distribution network fault using an active search method as described in Appendix 1, characterized in that it is the method described in Appendix 1.

[0056] (Note 4) The method for isolating and self-repairing a power distribution network fault according to Appendix 1, characterized in that the search signal injected from the distributed power source is intermittent, that is, after being injected for a certain period of time Tz, the injection is temporarily suspended for a certain period of time Tn, and such a cycle is repeated.

[0057] (Note 5) The operating conditions for the active search current protection are: (1) The active search signal is detected, and the signal current is greater than the current threshold set for protection. (2) The detected active search signal satisfies the discontinuous characteristics, (3) The duration of the active search signal is greater than the protected delay threshold, (4) The ratio of the active search current to the commercial frequency current is greater than the set threshold. An active search-type method for isolating and self-repairing power distribution network faults, as described in Appendix 4, characterized by including the following:

[0058] (Note 6) The procedure for determining whether a fault has been isolated based on changes in the voltage of an active search signal is as follows: The protective device includes collecting an active search voltage signal, calculating its symmetry, and determining that a fault has been isolated if the active search voltage changes from asymmetric to symmetric. Conditions for voltage asymmetry:

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[0059] (Note 7) An active search type method for isolating and self-repairing power distribution network faults, wherein each switch in the power distribution network is equipped with a protection device having a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, the commercial frequency current protection and the active search current protection work in a stepwise coordinated manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, the protection device has a fault self-repair function and determines whether the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, the power supply communication switch is closed to resume power supply to the healthy section, and the procedure for handling a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds a set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to eliminate the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault point detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the islanding distributed power supply actively injects the search signal S2, and (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section. An active search-type method for isolating and self-repairing power distribution network faults, characterized by including the following:

[0060] (Note 8) The method for gradual coordination between the fixed-time commercial frequency current protection and the fixed-time active search current protection, characterized in that the commercial frequency current protection is coordinated in stages starting from the forward direction, which is the direction in which current flows from the busbar to the power line, that is, the closer the protection device is to the power source, the longer the operating time becomes, and the active search current protection is coordinated in stages starting from the reverse direction, which is the direction in which current flows from the power line to the busbar, that is, the closer the protection device is to the power source, the shorter the operating time becomes, as described in Appendix 7, for the isolation and self-repair of an active search type power distribution network fault.

[0061] (Note 9) The search signal actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, or a pulsed square wave. And / or, the start time and duration of injecting the search signal from the distributed power supply can both be set, the start time being the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration being set to a set value. and / or, the time at which the search signal is injected from the distributed power supply is the set initial phase angle φ set Determined by, φ set It is an angle from 0 to 360°, and is usually set to 0°. The method for isolating and self-repairing a power distribution network fault using an active search method as described in Appendix 7, characterized in that it is the method described in Appendix 7.

[0062] (Note 10) The method for isolating and self-repairing a power distribution network fault according to Appendix 7, characterized in that the search signals S1 and S2 injected from the distributed power source have different waveforms.

[0063] (Note 11) The method for isolating and self-repairing a power distribution network fault according to Appendix 7, characterized in that the search signal injected from the distributed power source is intermittent, that is, after being injected for a certain time Tz, the injection is paused for a certain time Tn, and such a cycle is repeated.

[0064] (Note 12) The operating conditions for the active search current protection are: (1) The active search signal is detected, and the signal current is greater than the current threshold set for protection. (2) The detected active search signal satisfies the discontinuous characteristics, (3) The duration of the active search signal is greater than the protected delay threshold, (4) The ratio of the active search current to the commercial frequency current is greater than the set threshold. The method for isolating and self-repairing a power distribution network fault according to Appendix 11, characterized by including the following:

[0065] (Note 13) This is an active search-type power distribution network fault isolation and self-repair system, in which each switch in the power distribution network is equipped with a protective device that has a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and active search current protection work in a stepwise manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the power communication switch and resumes power supply to the healthy section, and the procedure for handling a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds a set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault point detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the protective device in the communication switch detects a change in the voltage of the active search signal, determines whether the fault has been isolated based on the change in the voltage of the active search signal, and if it determines that the fault has been isolated, closes the switch after a delay of t3 and resumes power supply to the healthy section. An active search-type power distribution network fault isolation and self-repair system characterized by the following:

[0066] (Note 14) This is an active search-type power distribution network fault isolation and self-repair system, in which each switch in the power distribution network is equipped with a protective device that has a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and active search current protection work in a stepwise coordinated manner with a time difference from the forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the power communication switch and resumes power supply to the healthy section, and the procedure for handling a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds a set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault point detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the islanding distributed power supply actively injects the search signal S2, (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section. An active search-type power distribution network fault isolation and self-repair system characterized by the following:

Claims

1. An active search type method for isolating and self-repairing power distribution network faults, wherein each switch in the power distribution network is equipped with a protection device having a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, the commercial frequency current protection and the active search current protection work in a stepwise coordinated manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, the protection device has a fault self-repair function and determines whether the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, the power supply communication switch is closed to resume power supply to the healthy section, and the procedure for handling a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds a set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault point detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault, and (4) After the fault is isolated, the protective device in the communication switch detects a change in the voltage of the active search signal, determines whether the fault has been isolated based on the change in the voltage of the active search signal, and if it is determined that the fault has been isolated, closes the switch after a delay of t3 and resumes power supply to the healthy section. An active search-type method for isolating and self-repairing power distribution network faults, characterized by including the following:

2. The method for staggered coordination between the fixed-time commercial frequency current protection and the fixed-time active search current protection, characterized in that the commercial frequency current protection is coordinated in stages starting from the forward direction, which is the direction in which current flows from the busbar to the power line, that is, the closer the protection device is to the power source, the longer the operating time becomes, and the active search current protection is coordinated in stages starting from the reverse direction, which is the direction in which current flows from the power line to the busbar, that is, the closer the protection device is to the power source, the shorter the operating time becomes, as described in claim 1, for the isolation and self-repair of an active search type power distribution network fault.

3. The search signal actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, or a pulsed square wave. And / or, the start time and duration of injecting the search signal from the distributed power supply can both be set, the start time being the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration being set to a set value. and / or, the time at which the search signal is injected from the distributed power supply is the set initial phase angle φ ｓｅｔ Determined by, φ ｓｅｔ It ranges from 0 to 360°, and is usually set to 0°. The method for isolating and self-repairing a power distribution network fault according to claim 1, characterized in that it is an active search type method.

4. The method for isolating and self-repairing a power distribution network fault according to claim 1, characterized in that the search signal injected from the distributed power source is intermittent, that is, after being injected for a certain time Tz, the injection is temporarily suspended for a certain time Tn, and such a cycle is repeated.

5. The operating conditions for the active search current protection are: (1) The active search signal is detected, and the signal current is greater than the current threshold set for protection. (2) The detected active search signal satisfies the discontinuous characteristics, (3) The duration of the active search signal is greater than the protected delay threshold, (4) The ratio of the active search current to the commercial frequency current is greater than the set threshold. The method for isolating and self-repairing a power distribution network fault according to claim 4, characterized by including the following:

6. The procedure for determining whether a fault has been isolated based on changes in the voltage of an active search signal is as follows: The protective device includes collecting an active search voltage signal, calculating its symmetry, and determining that a fault has been isolated if the active search voltage changes from asymmetric to symmetric. Conditions for voltage asymmetry: [Math 1] Voltage symmetry condition: [Math 2] where, U Ｚ１ , U Ｚ０ , U Ｚ２ are respectively the positive-phase, zero-phase, and negative-phase components of the active search voltage signal, k ｓｅｔ１ is the asymmetric threshold, U ｓｅｔ is the threshold of the positive-phase component of the active search voltage, U Ｇ１ is the positive-phase component of the commercial frequency voltage, k ｓｅｔ２ is the threshold of the ratio of the positive-phase components of the active search voltage and the commercial frequency voltage, and is characterized in that, the method for separating and self-repairing active search type distribution network faults according to claim 1.

7. An active search type method for isolating and self-repairing power distribution network faults, wherein each switch in the power distribution network is equipped with a protection device having a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, the commercial frequency current protection and the active search current protection work in a stepwise coordinated manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, the protection device has a fault self-repair function and determines whether the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, the power supply communication switch is closed to resume power supply to the healthy section, and the procedure for handling a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds a set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the islanding distributed power supply actively injects the search signal S2, and (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section. An active search-type method for isolating and self-repairing power distribution network faults, characterized by including the following:

8. The method for gradual coordination between the fixed-time commercial frequency current protection and the fixed-time active search current protection, characterized in that the commercial frequency current protection is coordinated in stages starting from the forward direction, which is the direction in which current flows from the busbar to the power line, that is, the closer the protection device is to the power source, the longer the operating time becomes, and the active search current protection is coordinated in stages starting from the reverse direction, which is the direction in which current flows from the power line to the busbar, that is, the closer the protection device is to the power source, the shorter the operating time becomes, as described in claim 7, for the isolation and self-repair of an active search type power distribution network fault.

9. The search signal actively injected from the distributed power supply is one or more combinations of the following: a two-part frequency sine wave, a three-part frequency sine wave, a higher-order harmonic above 250 Hz, an inter-order harmonic, or a pulsed square wave. And / or, the start time and duration of injecting the search signal from the distributed power supply can both be set, the start time being the time after the distributed power supply detects an isolated operation state and the injection begins after a set delay time has elapsed, and the duration being set to a set value. and / or, the time at which the search signal is injected from the distributed power supply is the set initial phase angle φ ｓｅｔ Determined by, φ ｓｅｔ It ranges from 0 to 360°, and is usually set to 0°. The method for isolating and self-repairing a power distribution network fault according to claim 7, characterized in that it is an active search type method.

10. The method for isolating and self-repairing a power distribution network fault according to claim 7, characterized in that the search signals S1 and S2 injected from the distributed power source have different waveforms.

11. The method for isolating and self-repairing a power distribution network fault according to claim 7, characterized in that the search signal injected from the distributed power source is intermittent, that is, after being injected for a certain time Tz, the injection is temporarily suspended for a certain time Tn, and such a cycle is repeated.

12. The operating conditions for the active search current protection are: (1) The active search signal is detected, and the signal current is greater than the current threshold set for protection. (2) The detected active search signal satisfies the discontinuous characteristics, (3) The duration of the active search signal is greater than the protected delay threshold, (4) The ratio of the active search current to the commercial frequency current is greater than the set threshold. The method for isolating and self-repairing a power distribution network fault according to claim 11, characterized by including the following:

13. This is an active search-type power distribution network fault isolation and self-repair system, in which each switch in the power distribution network is equipped with a protective device that has a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and active search current protection work in a stepwise manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the power supply communication switch and resumes power supply to the healthy section, and the procedure in the event of a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the protective device in the communication switch detects a change in the voltage of the active search signal, determines whether the fault has been isolated based on the change in the voltage of the active search signal, and if it is determined that the fault has been isolated, closes the switch after a delay of t3 and resumes power supply to the healthy section. An active search-type power distribution network fault isolation and self-repair system characterized by the following:

14. This is an active search-type power distribution network fault isolation and self-repair system, in which each switch in the power distribution network is equipped with a protective device that has a fixed-time commercial frequency current protection function and a fixed-time active search current protection function, and the commercial frequency current protection and active search current protection work in a stepwise manner with a time difference from forward and reverse directions to complete the isolation of the power distribution network fault, and the protective device has a fault self-repair function that determines whether or not the fault has been isolated by detecting a change in the voltage of the active search signal, and if the fault has been isolated, it closes the power communication switch and resumes power supply to the healthy section, and the procedure for handling a fault is as follows: (1) The protection device upstream of the fault point detects that the commercial frequency current exceeds the set threshold Iset1, and the protection device with a short delay time trips after a delay of t1 to remove the fault. (2) After the fault is removed, if the distributed power supply detects an islanding state, it changes its control strategy from current source control to voltage source control and actively injects the search signal S1. (3) The protection device downstream of the fault location detects that the current of the active search signal is greater than the threshold Iset2, and the protection device with a short delay time trips after a delay of t2 to isolate the fault. (4) After the fault is isolated, the isolated distributed power supply actively injects the search signal S2, (5) When the protective device in the communication switch detects that the active search signal has changed from S1 to S2, it determines that the fault has been isolated and closes the switch after a delay of t3 to resume power supply to the healthy section. An active search-type power distribution network fault isolation and self-repair system characterized by the following:

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