Ground fault line selection method and device for power distribution system, equipment and storage medium

Abstract

Embodiments of the application disclose a grounding fault line selection method and device for a power distribution system, equipment and a storage medium. The line selection method comprises: when it is determined that a permanent single-phase grounding fault occurs in the power distribution system, controlling the switch in the series structure to be closed to cause the resistor to be put into the power distribution system; obtaining first and second zero sequence currents of each feeder before and after the resistor is put in, and third and fourth zero sequence currents of a system neutral line of the power distribution system; using the first, second, third and fourth zero sequence currents to determine a change characteristic of the zero sequence current of each feeder after the resistor is put in, the change characteristic being used to reflect a change in the ratio of the zero sequence current of each feeder to the zero sequence current of the system neutral line before and after the resistor is put in; and determining a fault feeder of the power distribution system according to the change characteristic and a preset fault line selection rule. In this way, the fault feeder can be accurately selected when a permanent grounding fault occurs.

Description

Technical Field

[0001] This invention relates to the field of fault line location technology, and in particular to a method, apparatus, equipment and storage medium for selecting grounding faults in a power distribution system. Background Technology

[0002] In my country, single-phase grounding faults occur in up to nearly 80% of 6-35kV distribution network systems. Typically, distribution systems grounded via arc suppression coils are in an overcompensated state, exhibiting weak steady-state fault characteristics. This makes it impossible to determine the fault line based on power direction differences or zero-sequence current magnitudes. Furthermore, these systems suffer from low fault current and unstable arcs. When a permanent single-phase grounding fault occurs in a distribution network grounded via an arc suppression coil, although the three-phase voltages may remain symmetrical and allow operation with the fault for 1-2 hours, failure to disconnect the grounded fault section for an extended period can easily lead to insulation breakdown at weak points in the non-faulty phases, resulting in phase-to-phase short circuits and expanding the fault area. Therefore, timely and accurate fault location is crucial.

[0003] Meanwhile, with the rapid development of new energy sources and the gradual increase in the penetration rate of distributed power sources, more and more distributed power sources are being connected to the power grid through distribution lines. Generally speaking, in distribution networks containing distributed power sources, the transformers on the power source side of these sources are not grounded. Therefore, after a single-phase ground fault occurs, there is no zero-sequence current component on the system feeder other than the fault grounding point, which affects the reliable fault location for single-phase ground faults. Therefore, studying fault location for single-phase ground faults in distribution networks with distributed power source integration is of great significance. Summary of the Invention

[0004] The main objective of this invention is to provide a method, apparatus, equipment, and storage medium for selecting the line of a grounding fault in a power distribution system, which can solve the problem of the lack of reliable means for selecting the line of a single-phase grounding fault in a power distribution network with distributed power source access in the prior art.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for selecting the line of a grounding fault in a power distribution system. The power distribution system includes at least a distributed power source, a series structure, and several feeders. The series structure includes a switch and a resistor connected in series. The distributed power source is electrically connected to the feeders. One end of the series structure is electrically connected to the neutral point of any of the distributed power sources. The other end of the series structure is grounded.

[0006] The fault location method for the power distribution system includes:

[0007] When a permanent single-phase ground fault is determined to occur in the power distribution system, the switch in the series structure is controlled to close so that the resistor is connected to the power distribution system;

[0008] The first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected are obtained, as well as the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system.

[0009] Using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current, and the fourth zero-sequence current, the change characteristics of the zero-sequence current of each feeder after the resistor is put into operation are determined. The change characteristics are used to reflect the change of the ratio of the zero-sequence current of each feeder to the zero-sequence current of the neutral line of the system before and after the resistor is put into operation.

[0010] Based on the aforementioned change characteristics and preset fault line selection rules, the faulty feeder of the power distribution system is determined.

[0011] In one feasible implementation, determining the variation characteristics of the zero-sequence current of each feeder after the resistor is switched on, using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current, and the fourth zero-sequence current, includes:

[0012] Determine a first ratio between the first zero-sequence current and the third zero-sequence current; determine a second ratio between the second zero-sequence current and the fourth zero-sequence current;

[0013] The change characteristics are determined using the first ratio, the second ratio, and a preset difference algorithm.

[0014] In one feasible implementation, the difference algorithm is as follows:

[0015]

[0016] In the formula, For the variation characteristics of the i-th feeder, R DG The resistance value of the series structure. Let be the first zero-sequence current of the i-th feeder. The second zero-sequence current of the i-th feeder; It is the third zero-sequence current. This is the fourth zero-sequence current.

[0017] In one feasible implementation, determining the faulty feeder of the power distribution system based on the changing characteristics and preset fault selection rules includes:

[0018] If the variation characteristics of each feeder are all zero, then the faulty feeder is determined to be the j-th feeder, and the j-th feeder is the feeder where the target distributed power source is electrically connected to the series structure.

[0019] If the variation characteristics of the m-th feeder are opposite to those of the j-th feeder, and the variation characteristics of all feeders except the m-th and j-th feeders are zero, then the faulty feeder is determined to be the m-th feeder.

[0020] If the change characteristic of the j-th feeder is not zero, and the change characteristics of all other feeders except the j-th feeder are zero, then the faulty feeder is determined to be a bus.

[0021] In one feasible implementation, the method further includes, prior to:

[0022] Obtain the fifth zero-sequence current of the neutral line of the system;

[0023] If the fifth zero-sequence current is greater than the preset current threshold, it is determined that a single-phase ground fault has occurred in the power distribution system; and if the single-phase ground fault does not disappear after a preset delay time, it is determined that a permanent single-phase ground fault has occurred in the power distribution system, and the step of controlling the switch in the series structure to close so that the resistor is connected to the power distribution system when it is determined that a permanent single-phase ground fault has occurred in the power distribution system is executed.

[0024] If the fifth zero-sequence current is less than or equal to the preset current threshold, it is determined that no single-phase grounding fault has occurred in the power distribution system, and the process returns to the step of obtaining the fifth zero-sequence current of the neutral line of the system.

[0025] In one feasible implementation, the neutral point of the power distribution system is grounded via an arc suppression coil. After determining that a single-phase ground fault exists in the power distribution system, the process includes:

[0026] The arc suppression coil is used to extinguish the single-phase grounding fault.

[0027] If the single-phase ground fault does not disappear after the preset delay time, it is determined that a permanent single-phase ground fault has occurred in the power distribution system.

[0028] In one feasible implementation, obtaining the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is switched on, and the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system, includes:

[0029] The zero-sequence current of each feeder in the first power frequency cycle and the zero-sequence current of the neutral line in the system are respectively taken as the first zero-sequence current and the third zero-sequence current. The first power frequency cycle is one power frequency cycle before the resistor is put into operation for zero-sequence current sampling.

[0030] The zero-sequence current of each feeder in the second power frequency cycle and the zero-sequence current of the neutral line in the system are respectively used as the second zero-sequence current and the fourth zero-sequence current. The second power frequency cycle is one power frequency cycle of zero-sequence current sampling after the resistor is put into operation.

[0031] To achieve the above objectives, a second aspect of the present invention provides a fault location device for a grounding fault in a power distribution system. The power distribution system includes at least a distributed power source, a series structure, and several feeders. The series structure includes a switch and a resistor connected in series. The distributed power source is electrically connected to the feeders. One end of the series structure is electrically connected to the neutral point of any of the distributed power sources. The other end of the series structure is grounded.

[0032] The fault location device of the power distribution system includes:

[0033] Resistor connection module: used to control the switch in the series structure to close so that the resistor is connected to the power distribution system when a permanent single-phase ground fault is determined to have occurred in the power distribution system;

[0034] Current acquisition module: used to acquire the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected, as well as the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system.

[0035] Feature determination module: used to determine the change characteristics of the zero-sequence current of each feeder after the resistor is put into operation using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current and the fourth zero-sequence current. The change characteristics are used to reflect the change of the ratio of the zero-sequence current of each feeder to the zero-sequence current of the neutral line of the system before and after the resistor is put into operation.

[0036] Feeder selection module: used to determine the faulty feeder of the power distribution system based on the changing characteristics and preset fault selection rules.

[0037] To achieve the above objectives, a third aspect of the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps shown in the first aspect and any feasible implementation.

[0038] To achieve the above objectives, a fourth aspect of the present invention provides a computer device including a memory and a processor, the memory storing a computer program, which, when executed by the processor, causes the processor to perform the steps shown in the first aspect and any feasible implementation.

[0039] The embodiments of the present invention have the following beneficial effects:

[0040] This invention provides a method for selecting the fault location of a power distribution system. The power distribution system includes at least a distributed power source, a series structure, and several feeders. The series structure includes a switch and a resistor connected in series. The distributed power source is electrically connected to the feeders. One end of the series structure is electrically connected to the neutral point of any distributed power source, and the other end of the series structure is grounded. The fault location method for the power distribution system includes: when a permanent single-phase ground fault is determined to occur in the power distribution system, controlling the switch in the series structure to close so that the resistor is connected to the power distribution system; acquiring the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected, and the third zero-sequence current and the fourth zero-sequence current of the system neutral line of the power distribution system; using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current, and the fourth zero-sequence current, determining the change characteristics of the zero-sequence current of each feeder after the resistor is connected, the change characteristics reflecting the change in the ratio of the zero-sequence current of each feeder to the zero-sequence current of the system neutral line before and after the resistor is connected; and determining the faulty feeder of the power distribution system according to the change characteristics and a preset fault location rule. The above-mentioned line selection method allows for the introduction of a resistor into the power distribution system when a permanent grounding fault occurs. By comparing the changes in the ratio of zero-sequence current of each feeder to the neutral line before and after the resistor is introduced, the faulty feeder can be distinguished from the non-faulty feeder, thus completing the fault line selection. This method features simple logic, accurate line selection, and strong tolerance to transition resistance. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] in:

[0043] Figure 1 This is a topology diagram of a power distribution system according to an embodiment of the present invention;

[0044] Figure 2 This is a flowchart of a grounding fault selection method for a power distribution system according to an embodiment of the present invention;

[0045] Figure 3 This is another flowchart of a ground fault selection method for a power distribution system according to an embodiment of the present invention;

[0046] Figure 4(a) is a waveform diagram of the zero-sequence current of each feeder and neutral line when a single-phase metallic grounding fault occurs at k2 in an embodiment of the present invention.

[0047] Figure 4(b) is a waveform diagram of the zero-sequence current of each feeder and neutral line when a single-phase metallic grounding fault occurs at k3 in an embodiment of the present invention.

[0048] Figure 4(c) is a waveform diagram of the zero-sequence current of each feeder and neutral line when a single-phase metallic grounding fault occurs at k4 in an embodiment of the present invention.

[0049] Figure 5 This is a structural block diagram of a ground fault location device for a power distribution system according to an embodiment of the present invention;

[0050] Figure 6 This is a structural block diagram of a computer device in an embodiment of the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Please see Figure 1 , Figure 1 This is a topology diagram of a power distribution system according to an embodiment of the present invention. The power distribution system includes at least a distributed power source 101, a series structure, and several feeder lines. Further, the series structure consists of a switch and a resistor R connected in series. DG The distributed power source 101 is electrically connected to the feeder line. The fault location method in this application is based on a single-phase grounding fault location method for distribution networks using a transformer modified for the distributed power source side. Therefore, one end of the series structure is electrically connected to the neutral point of any distributed power source, and the other end of the series structure is grounded. The neutral point of the distribution system is connected via an arc suppression coil L. S Grounding. The distribution network can be an active distribution network, employing inverter-type distributed generation, and a resistor R connected in series with switch S is installed on the star-connected side of the distributed generation grid-connected transformer of any feeder j. DG In the active power distribution network system, the neutral point is grounded via an arc suppression coil, with a resistance R. DG After a permanent single-phase ground fault occurs in the system, it is switched on by closing switch S.

[0053] It should be noted that a series structure has only one distributed generation (DG) in the distribution network, while multiple DGs can be installed on feeders. In a series structure, one DG is connected to the distribution network at its neutral point. A feeder can be described as a power line, such as a cable, through which electricity passes in the power system. It transmits electricity from a substation to different distribution points; it is a power line from a utility substation or other power supply point to the customer. Figure 1 This example only illustrates a simplified distribution network topology consisting of one busbar connected to four feeders (line1, line2, line3, and line4), three distributed power sources, one main transformer, and a series structure. The specific number of feeders, types, and quantities of electrical equipment in the distribution network will vary depending on the actual situation. Figure 1 This is merely an illustrative example for this embodiment and is not intended to limit the scope of this application. Continue reading... Figure 1 , Figure 1 Four fault points, k1, k2, k3, and k4, are also shown.

[0054] Please see Figure 2 , Figure 2 This is a flowchart illustrating a ground fault location method for a power distribution system according to an embodiment of the present invention. This method can be applied to either a terminal or a server. The terminal can be a desktop terminal or a mobile terminal; a mobile terminal can be at least one of a mobile phone, tablet computer, or laptop computer. The server can be a standalone server or a server cluster composed of multiple servers. This embodiment uses a terminal as an example, wherein the terminal can have a communication connection with the aforementioned power distribution system and can manage and control the power distribution system; that is, the terminal can be a management terminal for the aforementioned power distribution system, such as... Figure 2 The method shown includes the following steps:

[0055] 201. When it is determined that a permanent single-phase ground fault has occurred in the power distribution system, the switch in the series structure is controlled to close so that the resistor is connected to the power distribution system;

[0056] It should be noted that during the operation of the power distribution system, its power data is monitored in real time to promptly understand the operating status of the power distribution system and detect faults and other abnormalities. Therefore, the moment when a permanent single-phase fault occurs in the power distribution system can be detected and confirmed. When it is determined that a permanent single-phase ground fault has occurred in the power distribution system, the switch in the series structure can be closed in a timely manner to connect the resistor to the power distribution system. The power data includes, but is not limited to, power parameters such as current, voltage, and power that can reflect the operating status of the power distribution system. This application mainly acquires the zero-sequence current data of the power distribution system, that is, this application mainly monitors the zero-sequence current data of the power distribution system in real time and uses the zero-sequence current data to monitor single-phase ground faults. In one feasible implementation, steps A01 to A03 are included before step 201 to achieve fault monitoring.

[0057] A01. Obtain the fifth zero-sequence current of the neutral line in the system;

[0058] A02. If the fifth zero-sequence current is greater than the preset current threshold, it is determined that a single-phase ground fault has occurred in the power distribution system; and if the single-phase ground fault does not disappear after a preset delay time, it is determined that a permanent single-phase ground fault has occurred in the power distribution system, and the step of controlling the switch in the series structure to close so that the resistor is connected to the power distribution system when it is determined that a permanent single-phase ground fault has occurred in the power distribution system is executed.

[0059] A03. If the fifth zero-sequence current is less than or equal to the preset current threshold, it is determined that no single-phase grounding fault has occurred in the power distribution system, and the process returns to the step of obtaining the fifth zero-sequence current of the neutral line of the system.

[0060] Understandably, the fifth zero-sequence current is the current zero-sequence current of the system neutral line before the resistor is connected. The presence of a single-phase ground fault is determined by constantly monitoring the state of the current zero-sequence current. Specifically, a current threshold I for triggering fault protection is pre-set. set I set Also known as the starting value, it is when the zero-sequence current is greater than I. set When the protection system is activated, it begins line selection. If the fifth zero-sequence current exceeds a preset current threshold, a single-phase ground fault is identified in the distribution system. If the single-phase ground fault does not disappear after a preset delay, a permanent single-phase ground fault is identified, and the system proceeds to close the switch in the series structure to connect the resistor to the distribution system. Conversely, if the fifth zero-sequence current is less than or equal to the preset current threshold, no single-phase ground fault is identified, and the system returns to the step of obtaining the fifth zero-sequence current of the neutral line. In other words, when a single-phase ground fault occurs, switch S is open, and the resistor is not connected to the system, thus not affecting the normal operation of the active distribution network.

[0061] In one feasible implementation, the neutral point of the power distribution system is grounded via an arc suppression coil. After determining that a single-phase ground fault exists in the power distribution system, the single-phase ground fault can be extinguished based on the arc suppression coil. If the single-phase ground fault does not disappear after a preset delay, the arc suppression is considered to have failed, and a permanent single-phase ground fault is determined to have occurred in the power distribution system, which is more accurate.

[0062] 202. Obtain the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected, as well as the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system.

[0063] Furthermore, after the resistor is connected to the system, the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected, as well as the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system, are obtained. Step 202 may include: taking the zero-sequence current of each feeder in the first power frequency cycle and the zero-sequence current of the neutral line of the system as the first zero-sequence current and the third zero-sequence current, respectively, where the first power frequency cycle is one power frequency cycle for zero-sequence current sampling before the resistor is connected; taking the zero-sequence current of each feeder in the second power frequency cycle and the zero-sequence current of the neutral line of the system as the second zero-sequence current and the fourth zero-sequence current, respectively, where the second power frequency cycle is one power frequency cycle for zero-sequence current sampling after the resistor is connected.

[0064] That is, sampling data for one power frequency cycle before and after the resistor is switched on is obtained as the node, and used as the zero-sequence current data before and after the resistor is switched on, and this data is used for subsequent line selection. Among them, the first zero-sequence current is the zero-sequence current of each feeder before the resistor is switched on, the second zero-sequence current is the zero-sequence current of each feeder after the resistor is switched on, the third zero-sequence current is the zero-sequence current of the neutral line of the system before the resistor is switched on, and the fourth zero-sequence current is the zero-sequence current of the neutral line of the system after the resistor is switched on.

[0065] For example, after a single-phase ground fault occurs in the system, the zero-sequence current forms a loop through the arc suppression coil. At this time, switch S remains open, and the resistor is not connected. Simultaneously, the small resistance R is sampled. DG Zero-sequence current of each outgoing line in the previous power frequency cycle and neutral zero-sequence current After a time interval δt, the fault is determined to be a permanent ground fault. At this time, switch S is closed, and the resistor is connected. The zero-sequence current of each outgoing line is obtained using FFT (Fast Fourier Transform) after a delay of 0.05s for one power frequency cycle. and neutral zero-sequence current

[0066] 203. Using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current and the fourth zero-sequence current, determine the change characteristics of the zero-sequence current of each feeder after the resistor is put into operation. The change characteristics are used to reflect the change of the ratio of the zero-sequence current of each feeder to the zero-sequence current of the neutral line of the system before and after the resistor is put into operation.

[0067] Then, after obtaining the zero-sequence current before and after the resistor is switched on, the first zero-sequence current, the second zero-sequence current, the third zero-sequence current and the fourth zero-sequence current are used to determine the change characteristics of the zero-sequence current of each feeder after the resistor is switched on, so as to know the change of the zero-sequence current and to determine which line has a fault based on the change.

[0068] In one feasible implementation, step 203 includes: determining a first ratio between the first zero-sequence current and the third zero-sequence current; determining a second ratio between the second zero-sequence current and the fourth zero-sequence current; and using the first ratio, the second ratio, and a preset difference algorithm to determine the variation characteristics of each feeder.

[0069] The difference algorithm can be used to calculate the difference between the first ratio and the second ratio, or it can be a difference amplification algorithm. When the difference algorithm is a difference amplification algorithm, the difference algorithm is as shown in equation (1):

[0070]

[0071] In the formula, For the variation characteristics of the i-th feeder, R DG The resistance value of the series structure. Let be the first zero-sequence current of the i-th feeder. The second zero-sequence current of the i-th feeder; It is the third zero-sequence current. This represents the fourth zero-sequence current, and i is the feeder number.

[0072] 204. Based on the aforementioned change characteristics and the preset fault selection rules, determine the fault feeder of the power distribution system.

[0073] In one feasible implementation, step 204 includes the following steps B01 to B03:

[0074] B01. If the variation characteristics of each feeder are all zero, then the faulty feeder is determined to be the j-th feeder, and the j-th feeder is the feeder where the target distributed power source is electrically connected to the series structure.

[0075] B02, If there exists a variation characteristic K for the m-th feeder. m The variation characteristic K of the j-th feeder j If the numbers are opposites of each other, and the variation characteristics of all feeders except the m-th feeder and the j-th feeder are zero, then the faulty feeder is determined to be the m-th feeder.

[0076] B03, if the variation characteristic K of the j-th feeder is... j If the value is not zero, and the variation characteristics of all feeders except the j-th feeder are zero, then the faulty feeder is determined to be the bus.

[0077] That is, according to the formula Calculate like If all values ​​are zero, then the j-th line (i.e., the line requiring modification) is considered faulty; if K exists... m=-K j (m≠j) and K i =0 (i = 1, 2, 3…, but i ≠ m and i ≠ j), then it is determined that the m-th line has a fault; if K j ≠0 and K i If the value of i = 0 (i = 1, 2, 3... and i ≠ j), then the busbar is considered to have a fault.

[0078] This invention provides a method for selecting the fault location of a power distribution system. The power distribution system includes at least a distributed power source, a series structure, and several feeders. The series structure includes a switch and a resistor connected in series. The distributed power source is electrically connected to the feeders. One end of the series structure is electrically connected to the neutral point of any distributed power source, and the other end of the series structure is grounded. The fault location method for the power distribution system includes: when a permanent single-phase ground fault is determined to occur in the power distribution system, controlling the switch in the series structure to close so that the resistor is connected to the power distribution system; acquiring the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected, and the third zero-sequence current and the fourth zero-sequence current of the system neutral line of the power distribution system; using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current, and the fourth zero-sequence current, determining the change characteristics of the zero-sequence current of each feeder after the resistor is connected, the change characteristics reflecting the change in the ratio of the zero-sequence current of each feeder to the zero-sequence current of the system neutral line before and after the resistor is connected; and determining the faulty feeder of the power distribution system according to the change characteristics and a preset fault location rule. Using the above-mentioned line selection method, when a permanent grounding fault occurs, a resistor can be connected to the power distribution system. By comparing the changes in the ratio of zero-sequence current of each feeder to the neutral line of the system before and after the resistor is connected, the faulty feeder can be distinguished from the non-faulty feeder, thus completing the fault line selection. The line selection logic is simple and accurate, and it has a strong ability to withstand transition resistance.

[0079] Please see Figure 3 , Figure 3 This is another flowchart of a ground fault location method for a power distribution system according to an embodiment of the present invention, as shown below. Figure 3 The method shown includes the following steps:

[0080] 301. Detect the neutral point zero-sequence current I0;

[0081] 302. Determine if I0 > I 0set If not, proceed to step 301; if yes, proceed to step 303.

[0082] 303. Extract the neutral point zero-sequence current I0 and the zero-sequence current I of each outgoing line. 0i ;

[0083] 304. Determine if the fault disappeared before the small resistor of line j was connected. If yes, proceed to step 301; otherwise, proceed to step 305.

[0084] 305. The small resistor R of the j-th line is activated. DG ;

[0085] 306. Calculate K for each branch line. i ;

[0086] 307. Determine K j =0? If yes, then line j is faulty (i.e., the situation corresponding to step B01 above); otherwise, proceed to step 308;

[0087] 308. Determine if K exists. m =-K j If yes, then determine that line m is faulty (i.e., the situation corresponding to step B02 above); otherwise, determine that the bus is faulty (i.e., the situation corresponding to step B03 above).

[0088] It should be noted that, Figure 3 The content of each step of the method shown is the same as Figure 2 The steps in the method shown are similar and will not be repeated here to avoid repetition. Please refer to [link to relevant documentation] for details. Figure 2 The content of each step in the method shown.

[0089] For example, you can continue to refer to Figure 1 , Figure 4(a) , 4(b) Figure 4(c) shows the waveforms of the zero-sequence currents of each feeder and neutral line when a single-phase metallic ground fault occurs at k2 in an embodiment of the present invention; Figure 4(b) shows the waveforms of the zero-sequence currents of each feeder and neutral line when a single-phase metallic ground fault occurs at k3 in an embodiment of the present invention; Figure 4(c) shows the waveforms of the zero-sequence currents of each feeder and neutral line when a single-phase metallic ground fault occurs at k4 in an embodiment of the present invention. Figure 1 The distributed power supply transformer for feeder line 3 shown uses a Y / Δ connection, and the neutral point on the Y side is connected in series with resistor R via switch S. DG Grounding. The system is configured to detect a metallic single-phase ground fault at t = 0.2s, and after a certain delay, determine the nature of the fault. If the fault is determined to be a permanent ground fault, the grounding resistance R of the distributed power source side transformer is adjusted at t = 0.6s. DG (100Ω) input.

[0090] This invention discloses a method for selecting the fault location of a single-phase grounding fault in a distribution network based on the grounding modification of a distributed power source side transformer. The method involves setting a resistor connected in series with a switch at the neutral point of the grid-connected star-type transformer connected to any feeder. When a permanent single-phase grounding fault occurs in the system, this resistor is activated. By comparing the changes in the ratio of the zero-sequence current of each feeder to the system neutral line before and after activating the resistor, the faulty feeder can be distinguished from the non-faulty feeder, thus enabling fault location. This invention features simple logic, accurate fault location, and strong tolerance to transition resistance.

[0091] Please see Figure 5 , Figure 5 This is a structural block diagram of a ground fault location device for a power distribution system according to an embodiment of the present invention, as shown below. Figure 5 The apparatus shown includes:

[0092] Resistor connection module 501: When it is determined that a permanent single-phase ground fault has occurred in the power distribution system, control the switch in the series structure to close so that the resistor is connected to the power distribution system;

[0093] Current acquisition module 502: used to acquire the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is put into operation, as well as the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system.

[0094] Feature determination module 503: used to determine the change characteristics of the zero-sequence current of each feeder after the resistor is put into operation by using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current and the fourth zero-sequence current. The change characteristics are used to reflect the change of the ratio of the zero-sequence current of each feeder to the zero-sequence current of the neutral line of the system before and after the resistor is put into operation.

[0095] Feeder selection module 504: used to determine the faulty feeder of the power distribution system based on the changing characteristics and preset fault selection rules.

[0096] It should be noted that, Figure 5 The contents of each module of the device shown are... Figure 2 The steps in the method shown are similar and will not be repeated here to avoid repetition. Please refer to [link to relevant documentation] for details. Figure 2 The content of each step in the method shown.

[0097] This invention provides a fault location device for a power distribution system. The power distribution system includes at least a distributed power source, a series structure, and several feeders. The series structure includes a switch and a resistor connected in series. The distributed power source is electrically connected to the feeders. One end of the series structure is electrically connected to the neutral point of any distributed power source, and the other end of the series structure is grounded. The fault location device for the power distribution system includes: a resistor activation module: used to control the switch in the series structure to close and activate the resistor when a permanent single-phase ground fault is determined in the power distribution system; a current acquisition module: used to acquire the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is activated, and the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system; a feature determination module: used to determine the change characteristics of the zero-sequence current of each feeder after the resistor is activated using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current, and the fourth zero-sequence current, the change characteristics reflecting the change in the ratio of the zero-sequence current of each feeder to the zero-sequence current of the neutral line before and after the resistor is activated; and a feeder selection module: used to determine the faulty feeder of the power distribution system according to the change characteristics and preset fault location rules. The aforementioned line selection device can be used to apply a resistor to the power distribution system when a permanent grounding fault occurs. By comparing the changes in the ratio of zero-sequence current of each feeder to the neutral line of the system before and after the resistor is applied, the faulty feeder can be distinguished from the non-faulty feeder, thus completing the fault line selection. It achieves simple logic, accurate line selection, and has a strong ability to withstand transition resistance.

[0098] Figure 6 An internal structural diagram of a computer device in one embodiment is shown. This computer device can specifically be a terminal or a server. Figure 6 As shown, the computer device includes a processor, memory, and a network interface connected via a system bus. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and may also store a computer program, which, when executed by the processor, causes the processor to perform the aforementioned methods. The internal memory may also store a computer program, which, when executed by the processor, causes the processor to perform the aforementioned methods. Those skilled in the art will understand that… Figure 6 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0099] In one embodiment, a computer device is provided, including a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform actions such as... Figure 2 or Figure 3 The steps of the method shown.

[0100] In one embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, causes the processor to perform the following actions: Figure 2 or Figure 3 The steps of the method shown.

[0101] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM), etc.

[0102] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0103] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for selecting the line of a grounding fault in a power distribution system, characterized in that, The power distribution system includes at least a distributed power source, a series structure, and several feeders. The series structure includes a switch and a resistor connected in series. The distributed power source is electrically connected to the feeders. One end of the series structure is electrically connected to the neutral point of any of the distributed power sources, and the other end of the series structure is grounded. The fault location method for the power distribution system includes: When a permanent single-phase ground fault is determined to occur in the power distribution system, the switch in the series structure is controlled to close so that the resistor is connected to the power distribution system; The first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected are obtained, as well as the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system. Using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current, and the fourth zero-sequence current, the change characteristics of the zero-sequence current of each feeder after the resistor is put into operation are determined. The change characteristics are used to reflect the change of the ratio of the zero-sequence current of each feeder to the zero-sequence current of the neutral line of the system before and after the resistor is put into operation. Based on the aforementioned change characteristics and preset fault selection rules, the faulty feeder of the power distribution system is determined; The step of determining the variation characteristics of the zero-sequence current of each feeder after the resistor is connected, using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current, and the fourth zero-sequence current, includes: Determine a first ratio between the first zero-sequence current and the third zero-sequence current; determine a second ratio between the second zero-sequence current and the fourth zero-sequence current; The change characteristics are determined using the first ratio, the second ratio, and a preset difference algorithm; The difference algorithm is as follows: ； In the formula, For the first i The variation characteristics of the feeder The resistance value of the series structure. For the first i The first zero-sequence current of the feeder. For the first i The second zero-sequence current of the feeder; It is the third zero-sequence current. This is the fourth zero-sequence current.

2. The method according to claim 1, characterized in that, The step of determining the faulty feeder of the power distribution system based on the change characteristics and preset fault selection rules includes: If the variation characteristics of each feeder are all zero, then the faulty feeder is determined to be the first one. j The feeder, the first j The feeder is the feeder of the target distributed power source that is electrically connected to the series structure; If there exists a first m The variation characteristics of the feeder are similar to those of the first feeder. j The variation characteristics of the feeders are opposites of each other, and except for the first... m The feeder and the first j If the variation characteristics of all feeders other than the faulty feeder are zero, then the faulty feeder is determined to be the faulty feeder. m One feeder line; If the first j The variation characteristics of the feeder are not zero, and except for the first... j If the variation characteristics of all feeders other than the faulty feeder are zero, then the faulty feeder is determined to be the busbar.

3. The method according to claim 1, characterized in that, The method is preceded by: Obtain the fifth zero-sequence current of the neutral line of the system; If the fifth zero-sequence current is greater than the preset current threshold, it is determined that a single-phase ground fault has occurred in the power distribution system; and if the single-phase ground fault does not disappear after a preset delay time, it is determined that a permanent single-phase ground fault has occurred in the power distribution system, and the step of controlling the switch in the series structure to close so that the resistor is connected to the power distribution system when it is determined that a permanent single-phase ground fault has occurred in the power distribution system is executed. If the fifth zero-sequence current is less than or equal to the preset current threshold, it is determined that no single-phase grounding fault has occurred in the power distribution system, and the process returns to the step of obtaining the fifth zero-sequence current of the neutral line of the system.

4. The method according to claim 3, characterized in that, If the neutral point of the power distribution system is grounded via an arc suppression coil, then after determining that a single-phase ground fault exists in the power distribution system, the process includes: The arc suppression coil is used to extinguish the single-phase grounding fault. If the single-phase ground fault does not disappear after the preset delay time, it is determined that a permanent single-phase ground fault has occurred in the power distribution system.

5. The method according to claim 1, characterized in that, The acquisition of the first and second zero-sequence currents of each feeder before and after the resistor is connected, and the third and fourth zero-sequence currents of the neutral line of the power distribution system, includes: The zero-sequence current of each feeder in the first power frequency cycle and the zero-sequence current of the neutral line in the system are respectively used as the first zero-sequence current and the third zero-sequence current. The first power frequency cycle is one power frequency cycle before the resistor is put into operation for zero-sequence current sampling. The zero-sequence current of each feeder in the second power frequency cycle and the zero-sequence current of the neutral line in the system are respectively used as the second zero-sequence current and the fourth zero-sequence current. The second power frequency cycle is one power frequency cycle of zero-sequence current sampling after the resistor is put into operation.

6. A ground fault location device for a power distribution system, characterized in that, The power distribution system includes at least a distributed power source, a series structure, and several feeders. The series structure includes a switch and a resistor connected in series. The distributed power source is electrically connected to the feeders. One end of the series structure is electrically connected to the neutral point of any of the distributed power sources, and the other end of the series structure is grounded. The fault location device of the power distribution system includes: Resistor connection module: used to control the switch in the series structure to close so that the resistor is connected to the power distribution system when a permanent single-phase ground fault is determined to have occurred in the power distribution system; Current acquisition module: used to acquire the first zero-sequence current and the second zero-sequence current of each feeder before and after the resistor is connected, as well as the third zero-sequence current and the fourth zero-sequence current of the neutral line of the power distribution system. Feature determination module: used to determine the change characteristics of the zero-sequence current of each feeder after the resistor is put into operation using the first zero-sequence current, the second zero-sequence current, the third zero-sequence current and the fourth zero-sequence current. The change characteristics are used to reflect the change of the ratio of the zero-sequence current of each feeder to the zero-sequence current of the neutral line of the system before and after the resistor is put into operation. Feeder selection module: used to determine the faulty feeder of the power distribution system based on the changing characteristics and preset fault selection rules; Specifically, the feature determination module is used to: determine a first ratio between the first zero-sequence current and the third zero-sequence current; determine a second ratio between the second zero-sequence current and the fourth zero-sequence current; and determine the change feature using the first ratio, the second ratio, and a preset difference algorithm. The difference algorithm is as follows: ； In the formula, For the first i The variation characteristics of the feeder The resistance value of the series structure. For the first i The first zero-sequence current of the feeder. For the first i The second zero-sequence current of the feeder; It is the third zero-sequence current. This is the fourth zero-sequence current.

7. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, the processor performs the steps of the method as described in any one of claims 1 to 5.

8. A computer device, comprising a memory and a processor, characterized in that, The memory stores a computer program that, when executed by the processor, causes the processor to perform the steps of the method as described in any one of claims 1 to 5.

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