A method for rapid fault location in active power distribution networks

Abstract

This invention discloses a rapid fault location method for active power distribution networks, comprising the following steps: real-time topology search to obtain adjacent switching devices and their states, forming a real-time connection relationship table of switches and a set of searched switching devices; obtaining the post-fault current amplitude and direction collected at each switch in the set of switching devices; reading the real-time connection relationship table of switches to obtain adjacent switches and their current amplitude and direction; determining whether the fault current direction of downstream switches is less than or equal to 0, if any switch has a current direction of "1", it is a non-fault section; if the fault current direction recorded by all switches in the section is less than or equal to 0, then the section is a fault section; for the fault section, continue searching for the next level section according to the switch with the maximum fault current, and verify whether the next section meets the characteristics of a non-fault section; outputting the fault section. This invention achieves rapid fault location in power distribution networks, meeting the real-time requirements for fault location, isolation, and power restoration in power distribution networks.

Description

Technical Field

[0001] This invention belongs to the field of power distribution automation, and relates to a method for rapid fault location when a power distribution line with a high proportion of distributed power sources experiences a fault. Background Technology

[0002] With the accelerated installation of renewable energy power generation capacity, especially the large-scale integration of photovoltaic and wind power sources into the distribution network in a distributed manner, the number of faulty lines in the distribution network has increased. To address the fault location problem in the distribution network after the integration of distributed power sources, numerous studies have proposed fault location methods that consider distributed power sources. Existing methods mainly include matrix methods and intelligent optimization algorithms.

[0003] The matrix method locates faults based on the state information of whether the feeder terminal units (FTUs) or fault passage indicators (FPIs) installed along the line detect fault currents. While its principle is clear and its calculation speed is fast, the location results are easily affected by erroneous information from the FTUs or FPIs. Intelligent optimization algorithms, on the other hand, obtain the desired state functions of each switch based on assumed line sections, establish a 0-1 integer optimization model with the approximation of the switch functions as the basic objective, and solve it using intelligent optimization algorithms. Existing research mainly focuses on improving the optimization model and seeking efficient intelligent solution algorithms.

[0004] As active distribution networks with distributed generation (DG) become larger and more complex in their topology and operation, fault location becomes increasingly difficult. The DG in these networks is primarily at the inverter interface, where the output short-circuit current is small, making detection errors more likely. Summary of the Invention

[0005] This invention addresses distribution networks with high-density distributed power source access. Based on the characteristic that the current amplitude of the faulty main path is greater than that of other paths, and combined with the power distribution terminal protection start signal, a rapid fault location method for medium-voltage lines in active distribution networks based on overheating path search is constructed, which meets the fault location requirements of distribution networks with high-density distributed power source access.

[0006] The technical solution adopted in this invention is a method for rapid fault location in active power distribution networks, comprising the following steps:

[0007] Step 1: After the feeder outlet circuit breaker trips, the fault location algorithm is started. First, a real-time topology search is performed to obtain the adjacent switching equipment and the status of the switches, and a real-time connection relationship table of the switches is formed. At the same time, a set of the searched switching equipment is formed.

[0008] Step 2: Obtain the post-fault current amplitude and direction collected at each switch in the switchgear set;

[0009] Step 3: Starting from the circuit breaker at the power distribution line outlet, search for the fault section and read the real-time connection table of the switches to obtain the adjacent switches and their current amplitude and current direction.

[0010] Step 4: Determine if the fault current direction of all downstream switches is less than or equal to 0. If there is a current direction of "1", it is a non-fault section. If the fault current direction recorded by all switches in the section is less than or equal to 0, then the section is a fault section.

[0011] Step 5: For the faulty section, continue to search for the next level section according to the switch with the maximum fault current, and check whether the next section meets the characteristics of a non-faulty section.

[0012] Step 6: Finally, output the faulty section.

[0013] Preferably, in step one, the search starts from the outgoing circuit breaker and extends to the line side. The search uses the breadth-first search (BFS) algorithm and forms a real-time connection table of switches after a fault. The topology search results are stored in a list format, and a Set collection class can be used to store the real-time topology search results D. Switching devices are used as key objects, and adjacent switches are used as value objects.

[0014] Preferably, for a centrally controlled feeder, the master station algorithm sequentially reads the adjacent switching equipment and the switch opening and closing status before the fault to determine its connectivity.

[0015] Preferably, for a distributed control feeder, the master control terminal sequentially reads the topology information of adjacent terminals and the switch opening and closing status of adjacent switching equipment before the fault through a point-to-point communication network to determine its connectivity.

[0016] Preferably, the direction of the fault current is defined as follows:

[0017] (a) When the FTU at the switch or the FPI on the line detects that the direction of the fault current is from the substation bus to the line, it is a positive direction and is represented by "1".

[0018] (b) When the FTU or FPI does not detect a fault current, it is indicated by "0";

[0019] (c) When the FTU or FPI detects that the direction of the fault current is from the line to the substation bus, it is in the opposite direction and is represented by "-1".

[0020] Preferably, for non-faulty sections, the magnitude of all current amplitudes in the section is compared. The current amplitude recorded by the switch with the current direction in the "1" state should not be less than the current amplitude of other switches. The switch with the largest current amplitude and the current direction in the "1" state is used as the key value. The real-time connection relationship table of the switches is read to determine the next section.

[0021] Preferably, when all smart distribution terminals on the feeder are installed, the communication parameters and local topology of the upstream and downstream adjacent smart distribution terminals are configured using the substation configuration language SCL. The local topology corresponds to the control area of ​​the corresponding smart distribution terminal, and the boundary between the control area and the control areas of other upstream and downstream terminals is the area from the monitored switch to the next monitored switch.

[0022] Preferably, the communication network adopts a network that supports point-to-point communication, uses a centralized control feeder, and the terminal communicates directly with the master station, which serves as the processing unit for fault location. For feeders with distributed control, the monitoring terminal of the first switch or the monitoring terminal of the tie switch can be used as the master control terminal, which serves as the initiator and processing unit for fault location. When all intelligent distribution terminals on the feeder are operating normally, they periodically transmit the switch opening and closing status and the detected voltage and current.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention targets distribution networks with high-density distributed power source integration. Based on the characteristic that the current amplitude of the main fault path is greater than that of other paths, and combining the distribution terminal protection start signal and the real-time topology search method, a rapid fault location method for active distribution networks based on overheating path search is constructed. In the fault location algorithm, fault current amplitude comparison and direction information are used simultaneously, which can reduce the impact of information distortion and improve the search speed, meeting the needs of rapid fault location in distribution networks with high-density distributed power source integration. Furthermore, the computational resources for fault location in distributed feeder automation mode are relatively small, requiring a distribution network fault location method with low computational load that can be implemented in the distribution terminal, thus better meeting the real-time requirements of fault location, isolation, and power restoration in distribution networks. This method is applicable to centralized or distributed feeder automation implementations of overhead distribution lines, cable lines, and overhead-cable hybrid lines. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method of the present invention;

[0026] Figure 2 This is a typical real-time example of a daisy-chain power distribution line; Detailed Implementation

[0027] The present invention will be further explained and described below with reference to the accompanying drawings to enable those skilled in the art to better understand it.

[0028] Example 1

[0029] The rapid fault location method in this invention operates at the main control terminal node in either a centralized feeder automation distribution substation or a distributed feeder automation mode. The main steps of the method are as follows:

[0030] 1) When installing all smart distribution terminals (STUs) on the feeder, the communication parameters and local topology of the upstream and downstream adjacent smart distribution terminals are configured using the substation configuration language (SCL). The local topology corresponds to the control area of ​​the corresponding STU. The boundary between this control area and the control areas of other upstream and downstream terminals is the area from the monitored switch to the next monitored switch.

[0031] 2) The communication network supports point-to-point communication and can be either a local area network (LAN) or a wide area network (WAN). For feeders using centralized control, the master station serves as the processing unit for fault location. For feeders using distributed control, the line head switch monitoring terminal serves as the master control terminal, acting as the initiator and processing unit for fault location. All STUs on the feeder periodically transmit switch opening / closing status and detected voltage and current during normal operation.

[0032] 3) The fault location algorithm is activated after the feeder output circuit breaker trips. For example... Figure 1-2 As shown, the specific operation is as follows:

[0033] Step 1: First, perform a real-time topology search to obtain adjacent switchgear and their status, and create a real-time connection table of the switches, as well as a set of the searched switchgear. Specifically, starting from the outgoing circuit breaker, the search proceeds towards the line side. For centrally controlled feeders, the master station performs a real-time topology search, sequentially reading adjacent switchgear and their pre-fault switch opening / closing status to determine connectivity. For distributed control feeders, the master control terminal sequentially reads the topology information of adjacent terminals and their pre-fault switch opening / closing status via a point-to-point communication network to determine connectivity.

[0034] The search employs a breadth-first search (BFS) algorithm and generates a real-time connection table of switches after a fault is detected.

[0035] To reduce algorithm resource consumption and facilitate fault location, the topology search results are stored in a list format during program development. The real-time topology search results D can be stored using a Set collection class, with the switching devices as key objects and adjacent switches as value objects.

[0036] Step 2: Obtain the post-fault current amplitude and direction from each switch in the switchgear set; the fault current direction is defined as follows:

[0037] (a) When the FTU at the switch or the FPI on the line detects that the direction of the fault current is from the substation bus to the line, it is a positive direction and is represented by "1".

[0038] (b) When the FTU or FPI does not detect a fault current, it is indicated by "0";

[0039] (c) When the FTU or FPI detects that the direction of the fault current is from the line to the substation bus, it is in the opposite direction and is represented by "-1".

[0040] Step 3: Starting from the circuit breaker at the power distribution line outlet, search for the fault section and read the real-time connection table of the switches to obtain the adjacent switches and their current amplitude and current direction.

[0041] Step 4: Determine if the fault current direction of all downstream switches is less than or equal to 0. If there is a current direction in the "1" state, it is a non-fault section. For non-fault sections, compare the magnitude of all current values ​​in the section. The current magnitude recorded by the switch with the current direction in the "1" state should not be less than the current magnitude of other switches. Use the switch with the largest current magnitude and the current direction in the "1" state as the key value, read the real-time connection relationship table of the switches, and proceed to the next section identification.

[0042] If the fault current direction recorded by all switches in this section is less than or equal to 0, it means that the fault current of all switches is flowing to this section, and this section is a fault section.

[0043] Step 5: For the faulty section, continue to search for the next level section according to the switch with the maximum fault current, and check whether the next section meets the characteristics of a non-faulty section.

[0044] Step 6: Finally, output the faulty section.

[0045] This invention provides a rapid fault location scheme for medium-voltage lines in active distribution networks with a high proportion of distributed power sources. Based on the characteristic that the current amplitude of the fault main path is greater than that of other paths, and combined with the power distribution terminal protection start signal, this invention constructs a scheme for rapid fault location of medium-voltage lines in active distribution networks based on overheat path search.

Claims

1. A method for rapid fault location in an active power distribution network, characterized in that, Includes the following steps: Step 1: After the feeder outlet circuit breaker trips, the fault location algorithm is started. First, a real-time topology search is performed to obtain the adjacent switching equipment and the status of the switches, and a real-time connection relationship table of the switches is formed. At the same time, a set of the searched switching equipment is formed. Step 2: Obtain the post-fault current amplitude and direction collected at each switch in the switchgear set; Step 3: Starting from the circuit breaker at the power distribution line outlet, search for the fault section and read the real-time connection table of the switches to obtain the adjacent switches and their current amplitude and current direction. Step 4: Determine if the fault current direction of all downstream switches is less than or equal to 0. If any switch has a current direction of "1", it is a non-faulty section. If all switches in the section record fault current directions less than or equal to 0, then the section is a faulty section. For non-faulty sections, compare the magnitude of all current values ​​in the section. The current magnitude recorded by the switch with a current direction of "1" should not be less than the current magnitude of other switches. Use the switch with the largest current magnitude and a current direction of "1" as the key value, read the real-time connection table of the switches, and proceed to the next section identification. Step 5: For the faulty section, continue to search for the next level section according to the switch with the maximum fault current, and check whether the next section meets the characteristics of a non-faulty section. Step 6: Finally, output the faulty section.

2. The method for rapid fault location in an active power distribution network according to claim 1, characterized in that, Step one starts with the outgoing circuit breaker and searches outwards to the line side. The search uses the breadth-first search (BFS) algorithm and forms a real-time connection table of switches after a fault. The topology search results are stored in a list format, and a Set collection class can be used to store the real-time topology search results D. Switching devices are used as key objects, and adjacent switches are used as value objects.

3. The method for rapid fault location in an active power distribution network according to claim 2, characterized in that, For feeders with centralized control, the master station algorithm sequentially reads the adjacent switching equipment and the switch opening and closing status before the fault to determine its connectivity.

4. The method for rapid fault location in an active power distribution network according to claim 2, characterized in that, For a distributed control feeder, the master control terminal sequentially reads the topology information of adjacent terminals and the switch opening and closing status of adjacent switching equipment before the fault through a point-to-point communication network to determine its connectivity.

5. The method for rapid fault location in an active power distribution network according to claim 1, characterized in that, The direction of fault current is defined as follows: (a) When the FTU at the switch or the FPI on the line detects that the direction of the fault current is from the substation bus to the line, it is a positive direction and is represented by "1". (b) When the FTU or FPI does not detect a fault current, it is indicated by "0"; (c) When the FTU or FPI detects that the direction of the fault current is from the line to the substation bus, it is in the opposite direction and is represented by "-1".

6. The method for rapid fault location in an active power distribution network according to claim 1, characterized in that, When all smart distribution terminals on the feeder are installed, the communication parameters and local topology of the upstream and downstream adjacent smart distribution terminals are configured using the substation configuration language SCL. The local topology corresponds to the control area of ​​the corresponding smart distribution terminal. The boundary between this control area and the control areas of other upstream and downstream terminals is the area from the monitored switch to the next monitored switch.

7. The method for rapid fault location in an active power distribution network according to claim 1, characterized in that, The communication network adopts a point-to-point communication network and a centralized control feeder. The terminal communicates directly with the master station, which serves as the processing unit for fault location. The feeder with distributed control uses the line head switch monitoring terminal or tie switch monitoring terminal as the master control terminal, which acts as the initiator and processing unit for fault location. All intelligent distribution terminals on the feeder periodically transmit the switch opening and closing status and the detected voltage and current when they are running normally.

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