Single-phase earth fault locating method and system for medium voltage distribution network based on weak communication

Abstract

A weak communication-based medium-voltage distribution network single-phase grounding fault positioning method and system, the method comprising: collecting the operation parameters of the distribution node in real time based on a set sampling frequency; dividing the minimum isolation range of the fault with a single feeder; filtering out the system imbalance component according to the sampling period variation of the zero sequence voltage and the zero sequence current, and extracting the fault component according to the set characteristic frequency band; extracting the direct current offset component of the node, calculating the transient energy of the zero sequence current fault component and the direction of the zero sequence current; identifying the minimum isolation range according to the sufficient and necessary conditions of the fault section, tripping the corresponding node switch, and when the tripping fails, tripping the upper adjacent node switch on the power supply side; the tie switch is time-lagged and delayed to close, and the power supply of the healthy area downstream of the fault is restored. The application realizes accurate positioning and minimum isolation of the single-phase grounding fault section of the distribution network, and improves the operation safety and power supply reliability of the distribution network.

Description

Technical Field

[0001] This application belongs to the field of medium-voltage distribution network technology, and relates to the handling of single-phase grounding faults in medium-voltage distribution networks, and particularly to a method and system for locating single-phase grounding fault sections in medium-voltage distribution networks based on weak communication. Background Technology

[0002] my country's power distribution network is mainly a low-current grounding system, among which single-phase grounding faults are the most common type of fault, accounting for more than 80% of all faults. When a single-phase grounding fault occurs in the system, the fault current can only form a path through the system's ground capacitance, resulting in a weak fault characteristic signal amplitude. Coupled with the background harmonic interference generated by nonlinear components such as distributed power sources and power electronic converters connected on a large scale in the power distribution network, the fault characteristics are becoming increasingly difficult to identify.

[0003] Traditional methods rely on single distribution automation terminal data or single feature analysis, lacking interactive verification of fault characteristics across multiple nodes. The polarities of the upstream and downstream zero-sequence currents at the grounding point are opposite and highly similar, but when the polarity of the zero-sequence current transformer is unclear, the correlation coefficient method has a blind spot in fault location and insufficient fault tolerance.

[0004] Traditional handling methods such as manual testing take 1-2 hours and are prone to causing continuous arcing at the fault point, leading to phase-to-phase short circuits and expanding the power outage area. According to statistics, about 35% of phase-to-phase faults are caused by untreated single-phase grounding faults, which seriously threaten personal safety and power supply reliability. Summary of the Invention

[0005] The purpose of this application is to propose a method and system for locating single-phase grounding faults in medium-voltage distribution networks based on weak communication, which solves the problems mentioned in the background art and is applicable to all medium-voltage distribution network systems.

[0006] This application adopts the following technical solution. The first aspect of this application provides a method for locating single-phase ground faults in medium-voltage distribution networks based on weak communication, comprising the following steps:

[0007] Based on the set sampling frequency, each node acquires the zero-sequence voltage and zero-sequence current sampling values ​​in real time.

[0008] Each node calculates the change in the zero-sequence voltage sampling period and the change in the zero-sequence current sampling period based on the zero-sequence voltage and zero-sequence current sampled values.

[0009] Each node calculates the dynamic data window length based on the change in the zero-sequence voltage sampling period;

[0010] According to the zero sequence current sampling period variation, fault component in a characteristic frequency band is extracted; transient energy of the fault component in the characteristic frequency band and current direction in a dynamic data window length are calculated; and according to the zero sequence current sampling period variation, a direct current offset component is calculated;

[0011] Each distribution node is connected with adjacent distribution nodes based on weak communication, each node interacts with any node outside the node, based on horizontal comparison of fault component transient energy, current direction and direct current offset component of all nodes, whether it is bus fault is judged, if it is bus fault, it is alarmed, if it is not bus fault, the minimum isolation range is identified, the node switch at the boundary of the minimum isolation range is tripped, and the tie switch outside the minimum isolation range is closed after delay, and the power supply of the healthy area downstream of the fault is restored.

[0012] Preferably, the single-phase grounding fault positioning method of the medium-voltage distribution network further comprises: dividing the fault minimum isolation range by single feeders;

[0013] Wherein, the area surrounded by the main line section switch and branch / interface switch, and the branch switch and interface switch, which does not contain the switch with protection outlet, is taken as the fault minimum isolation range.

[0014] Preferably, the single-phase grounding fault positioning method of the medium-voltage distribution network further comprises: establishing the information interaction category and format between nodes;

[0015] Wherein, the 0th and 1st bits of the 1st byte store the in-zone fault signal and out-zone fault signal respectively, the 2nd and 3rd bits store the tripping success signal and tripping failure signal respectively, the 4th bit stores the zero sequence current direction signal, the 5th bit stores the direct current offset overrun signal, and the 2nd and 3rd bytes store the transient energy of the fault component of the node.

[0016] Preferably, the extraction of the fault component in the characteristic frequency band according to the zero sequence current sampling period variation comprises:

[0017] The zero sequence current sampling period variation is filtered by a band-pass filter to extract the fault component in the characteristic frequency band of the band-pass filter;

[0018] For the neutral point ungrounded system, the characteristic frequency band of the band-pass filter is the capacitive frequency band ranging from 0 to the frequency at which the first series resonance of the zero sequence network occurs;

[0019] For the arc suppression coil grounding system, the characteristic frequency band of the band-pass filter is the capacitive frequency band ranging from the zero sequence line frequency band of the arc suppression coil to the frequency at which the first series resonance of the zero sequence network occurs.

[0020] Preferably, the calculation of the dynamic data window length by each node according to the zero sequence voltage sampling period variation comprises:

[0021] Obtain the variation of zero sequence voltage sampling period of each 2 cycle length before and after the single-phase ground fault moment; based on the data buffer timing, screen out the extreme point, confirm the moment as t1, and take it as the starting point to screen out the first peak point t2, the dynamic data window length between the moment t1 and the moment t2.

[0022] Preferably, the calculation of the transient energy of the fault component in the characteristic frequency band in the dynamic data window and the current direction comprises:

[0023] Between the moment t1 and the moment t2, the transient energy of the fault component in the characteristic frequency band is calculated for each sampling point, and the sum is obtained to obtain the transient energy of the fault component in the characteristic frequency band in the dynamic data window;

[0024] The relative position of the node and the fault point is used to determine the current direction.

[0025] Preferably, the calculation of the direct current offset component based on the variation of the zero sequence current sampling period comprises:

[0026] The direct current offset component is taken as a parameter to construct a fitting model current expression, and the least square sum of residuals is taken as an objective to obtain the direct current offset component by iterative nonlinear least squares fitting.

[0027] Preferably, the horizontal comparison of the transient energy of the fault component of all nodes, the current direction and the direct current offset component to determine whether it is a bus fault comprises:

[0028] The necessary and sufficient condition for fault section judgment is that the transient energy of the zero sequence current of the node is much larger than that of other nodes, or the transient energy of the zero sequence current of the node is larger than that of other nodes and in different directions, or only the direct current offset component of the zero sequence current of the node is larger than the threshold value, otherwise it is a bus fault.

[0029] Preferably, the interaction of each node with any node other than the node comprises: the node close to the power supply side trips, the remaining nodes in the minimum isolation range of the fault receive the "trip success" command or detect the voltage loss and trip, and the fault section is isolated; if the trip fails, the trip failure information is sent to the upper adjacent node on the power supply side, and when the "trip failure" information is received, the switch of the above-mentioned node is immediately tripped if it is in the closed state.

[0030] Preferably, the delay closing of the tie switch restores the power supply of the healthy area downstream of the fault comprises:

[0031] When the voltage on the side of the tie switch is lower than the threshold value, the delay closing is performed to restore the power supply of the healthy area downstream of the fault;

[0032] When the tie switch needs to be reclosed with the outgoing switch of the substation, the delay closing logic needs to be started after the reclosing fails.

[0033] The second aspect of the application provides a weak communication-based single-phase grounding fault positioning system for a medium-voltage distribution network, comprising a data acquisition module, a band-pass filtering module, a feature extraction module, a fault isolation module and a fault recovery module.

[0034] The data acquisition module is configured to acquire zero-sequence voltage and zero-sequence current analog quantities in real time at a set sampling frequency.

[0035] The band-pass filtering module is configured to calculate a zero-sequence voltage period variation and a zero-sequence current sampling period variation, and extract fault components in a characteristic frequency band.

[0036] The feature extraction module is configured to calculate a dynamic data window length according to the zero-sequence voltage sampling period variation, calculate a direct current offset component and calculate transient energy of fault components in the characteristic frequency band and a current direction within the dynamic data window length according to the zero-sequence current sampling period variation.

[0037] The fault isolation module is configured to interact with any node outside the node, compare the transient energy of fault components, the current direction and the direct current offset component of all nodes horizontally, determine whether it is a bus fault, and if it is a bus fault, alarm, and if it is not a bus fault, identify the minimum isolation range and trip the node switch at the boundary of the minimum isolation range.

[0038] The fault recovery module is configured to close the tie switch outside the minimum isolation range after a delay, and restore power supply to the healthy area downstream of the fault.

[0039] Preferably, the weak communication-based single-phase grounding fault positioning system for a medium-voltage distribution network further comprises a region division module, and the region division module is configured to divide the minimum fault isolation range with a single feeder and establish a type and format of information interaction between nodes.

[0040] Preferably, the region division module establishes the type and format of information interaction between nodes, comprising:

[0041] The 0th and 1st bits of the 1st byte store an in-zone fault signal and an out-of-zone fault signal, respectively, the 2nd and 3rd bits store a tripping success signal and a tripping failure signal, respectively, the 4th bit stores a zero-sequence current direction signal, the 5th bit stores a direct current offset overrun signal, and the 2nd and 3rd bytes store transient energy of fault components of the node.

[0042] The third aspect of the application provides an electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the computer program, when loaded into the processor, implements the weak communication-based single-phase grounding fault positioning method for a medium-voltage distribution network according to the first aspect.

[0043] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements a method for locating single-phase grounding faults in a medium-voltage distribution network based on weak communication, as described in the first aspect.

[0044] Compared with the prior art, the beneficial effects of this application include at least the following:

[0045] 1) This application avoids the influence of power frequency compensation of arc suppression coil by unbalanced filtering and characteristic frequency band extraction, so as to achieve the maximum transient zero-sequence current amplitude and the opposite direction of the flow to the healthy line at all times;

[0046] 2) This application enables reliable identification of fault sections when a fault occurs near the initial angle zero degree in the arc suppression coil grounding system by extracting the DC offset component of the node zero-sequence current;

[0047] 3) The application improves the adaptability of high-resistance grounding faults by exchanging zero-sequence current transient energy between nodes during the fault location process.

[0048] 4) This application sets the information exchange format between nodes, which has low requirements for channel bandwidth and latency. At the same time, it adopts a fault-triggered transmission mechanism to reduce communication traffic costs and improve adaptability to multiple application scenarios.

[0049] 5) This application considers the abnormal working condition of node switch tripping failure within the minimum fault isolation range. By using the interconnection tripping method of adjacent nodes at the upper level on the power supply side, the risk of fault range expansion caused by fault isolation failure is avoided, thereby improving the operation safety and power supply reliability of the distribution network. Attached Figure Description

[0050] Appendix Figure 1 A schematic diagram illustrating a method for locating single-phase grounding fault sections in a medium-voltage distribution network based on weak communication, as described in a specific embodiment of this application.

[0051] Appendix Figure 2 A schematic diagram illustrating the application of a single-phase grounding fault location system for a medium-voltage distribution network based on weak communication, provided in this application.

[0052] Appendix Figure 3 This is a schematic diagram based on an application example of a fault in the main line between sectionalizing switches FS1 and FS2, provided in this application.

[0053] Appendix Figure 4 This is a schematic diagram showing that node FS1 within the minimum isolation range of #2 meets the conditions for fault section location analysis, based on the application example provided in this application.

[0054] Appendix Figure 5 This is a schematic diagram of the node switch FS1 tripping failure provided in the application example of this application;

[0055] Figure 2 is a schematic diagram of a power supply system according to an embodiment of the present application; Figure 6 Figure 3 is a schematic diagram of a power supply system according to an embodiment of the present application;

[0056] Figure 4 is a schematic diagram of a power supply system according to an embodiment of the present application; Figure 7 Figure 5 is a schematic diagram of a power supply system according to an embodiment of the present application. DETAILED DESCRIPTION

[0057] Reference will now be made to the exemplary embodiments of the present application with reference to the accompanying drawings, however, the present application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art. The terminology used in the description of the exemplary embodiments presented herein is not intended to be limiting in scope, and is only used to convey the general nature of the present application to those skilled in the art. In the drawings, like reference numerals indicate like elements throughout the several views.

[0058] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0059] As shown in Figure 1, an embodiment of the present application provides a weak communication-based medium-voltage power distribution network single-phase ground fault section positioning method, which is suitable for a full-area weak communication on-site distributed power distribution system, and realizes rapid positioning and isolation of a single-phase ground fault section of the power distribution network, rapid recovery of power supply, and improvement of operational safety and stability of the power distribution network, and shortening of unnecessary power outage time of a healthy area. Figure 1 The main steps of the weak communication-based medium-voltage power distribution network single-phase ground fault section positioning method include: area division, data acquisition, band-pass filtering, feature extraction, fault isolation, and fault recovery; wherein each power distribution node and an adjacent power distribution node are connected to each other based on weak communication, for example but not limited to, based on 4G / carrier.

[0060] The specific steps of the weak communication-based medium-voltage power distribution network single-phase ground fault section positioning method include:

[0061] Step 1, area division, including: dividing a minimum isolation range of a fault based on a single feeder, and establishing a type and format of information interaction between nodes.

[0062] Preferably, the minimum isolation range of the fault section, i.e., an area surrounded by a trunk line section switch and a branch / junction switch, a branch switch and a junction switch, no longer contains a switch with a protection outlet inside.

[0063]

[0064] ​Preferably, the inter-node interaction information and format are set to set the data length of the number of bytes, and the format of storing the fault location, tripping result, and fault characteristics. Preferably but not limitedly, the 0thand 1stbits of the 1stbyte store the in-zone fault signal and the out-zone fault signal, respectively, the 2ndand 3rdbits store the tripping success signal and the tripping failure signal, respectively, the 4thbit stores the zero sequence current direction signal, the 5thbit stores the DC offset out-of-limit signal, and the 2ndand 3rdbytes store the transient energy of the node. Specifically, the following table is used to represent:

[0065] Table 1: Example of inter-node interaction information and format

[0066]

[0067] Step 2: Data acquisition, including: based on the set sampling frequency, real-time acquisition of the operating parameters of the power distribution node, specifically, based on the set sampling frequency, real-time acquisition of the zero sequence voltage and zero sequence current analog quantities of each node in the control area.

[0068] Preferably, the sampling frequency is set to be more than twice the highest frequency in the high-frequency transient component of the fault arc, which can be expressed by the following formula:

[0069] f s >2× f max

[0070] In the formula:

[0071] f s is the set sampling frequency; f max is the highest frequency in the high-frequency transient component of the fault arc.

[0072] The highest frequency in the high-frequency transient component of the fault arc f max Generally between 2-5 kHz, preferably but not limitedly, the sampling frequency f s Can be set to 12.8 kHz.

[0073] Step 3: Band-pass filtering, including: after a single-phase ground fault occurs, based on the data acquisition result of step 2, calculating the sampling period variation of the zero sequence voltage and the zero sequence current, filtering out the system imbalance component, and extracting the fault component according to the set characteristic frequency band.

[0074] Preferably, the way of calculating the sampling period variation of the zero sequence voltage and the zero sequence current and filtering out the system imbalance component is expressed by the following formula:

[0075] Δi x (t ) = i x ( t ) - i x ( t - N × ΔT )

[0076] Δu x ( t ) = u x ( t ) - u x ( t - N × ΔT )

[0077] In the formula:

[0078] Δu x (t), Δi x (t) represents the nodes. x Place t Changes in zero-sequence voltage and zero-sequence current sampling period at any given time;

[0079] ΔT This is the sampling interval time;

[0080] N This represents the number of sampling points within one power frequency cycle.

[0081] u x ( t ), i x ( t ) are nodes x Place t Sampled values ​​of zero-sequence voltage and zero-sequence current at any given time;

[0082] u x ( t - N × ΔT ), i x ( t - N × ΔT ) is a node x Place t The sampled values ​​of zero-sequence voltage and zero-sequence current corresponding to the previous cycle.

[0083] Preferably, based on nodes x Placet The manner of extracting the fault component in the characteristic frequency band according to the zero-sequence current sampling period variation is expressed by the following formula:

[0084]

[0085] In the formula:

[0086] is the node x is the filtered zero-sequence current fault component at the node

[0087] FIR is a band-pass filter.

[0088] Further preferably, the band-pass filter characteristic frequency band selection calculation method is as follows:

[0089] For a neutral non-grounded system, the capacitive frequency band range is 0 f c , i.e. between 0 and the first series resonance frequency of the zero-sequence network; for an arc suppression coil grounded system, the capacitive frequency band range is f arc ~ f c , wherein f arc is the zero-sequence line frequency band where the arc suppression coil is located, usually 2-3 times the system power frequency.

[0090] Further, f c is the first series resonance frequency of the zero-sequence network, expressed by the following formula:

[0091]

[0092] In the formula:

[0093] L is the longest line length of the system;

[0094] L 0, C 0 is the unit length inductance and capacitance.

[0095] Step 4, feature extraction, including: calculating the transient energy and current direction of the fault component in the zero-sequence current characteristic frequency band according to the zero-sequence current sampling period variation.

[0096] Preferably, the dynamic data window length is calculated according to the zero-sequence voltage sampling period variation, specifically including:

[0097] Obtaining the zero-sequence voltage sampling period variation of each 2-cycle length before and after the single-phase ground fault time;

[0098] Based on the data buffer timing, the extreme point is screened out, the time t1 is confirmed, and the first peak point t2 is screened out with the time t1 as the starting point. The dynamic data window length is between the time t1 and the time t2.

[0099] More specifically, the necessary and sufficient condition for judging the time t1, i.e. the extreme point, is expressed by the following formula:

[0100]

[0101] In the formula:

[0102] Δu x t is the zero sequence voltage sampling period change amount at the node x at the time t1. t Δu x x is the zero sequence voltage sampling period change amount at the node at the time t1.

[0103] The necessary and sufficient condition for judging the time t2, i.e. the first peak point, is expressed by the following formula:

[0104]

[0105] In the formula:

[0106] Δu x Δu x x is the zero sequence voltage sampling period change amount at the node

[0107] Therefore, the dynamic data window ΔT is calculated by the following formula:

[0108]

[0109] In the formula:

[0110] ΔT is the dynamic data window;

[0111] t1 and t2 are the time of the extreme point and the time of the first peak point, respectively.

[0112] Preferably, the direct current offset component calculation method comprises: constructing a fitting model current expression, which is expressed by the following formula:

[0113]

[0114] In the formula:

[0115] i ​​​​(t) is the fitting model current expression;

[0116] I dc is the DC offset amplitude;

[0117] τ is the time constant, preferably but not limited to, 20~50ms for cable line and 10~30ms for overhead line;

[0118] I ac is the AC amplitude.

[0119] It can be understood that the left side of the above formula is the model current expression of zero sequence current, and the right side is the form of zero sequence current expressed as the sum of DC offset component and AC component.

[0120] The residual square sum is minimized, and is obtained by iterative method of nonlinear least squares fitting I dc , which is expressed by the following formula:

[0121]

[0122] In the formula:

[0123] Δi x is the zero sequence current sampling period change at the moment of node t . x t

[0124] i is the fitting model current expression. t Preferably, the fault component transient energy and current direction in the characteristic frequency band of zero sequence current are calculated in the dynamic data window range, and the calculation method is expressed by the following formula:

[0125]

[0126]

[0127] In the formula:

[0128] E x is the zero sequence current transient energy at node x .

[0129] D x is the zero sequence current direction at node x .

[0130] ​​​Step 5, fault isolation, including: with the inter-node interaction information and format established in step 1, inter-node fault information interaction is carried out, the minimum isolation range is identified according to the necessary and sufficient conditions of fault section, the corresponding node switch is tripped, when the tripping fails, the adjacent node switch on the power side is tripped, and if it is judged as a bus fault, only an alarm is given.

[0131] Preferably, according to the inter-node interaction information and format established in step 1, each node sends fault information to any node outside the node x, including but not limited to: zero sequence current direction, zero sequence current transient energy, zero sequence DC offset overrun, etc.

[0132] Preferably, the necessary and sufficient conditions for fault section judgment are that the transient energy of the zero sequence current of the node is much larger than that of other nodes, or the transient energy of the zero sequence current of the node is larger than that of other nodes and in different directions, or only the DC offset component of the zero sequence current of the node is larger than the threshold value, otherwise it is a bus fault, which is specifically expressed by the following formula:

[0133]

[0134] In the formula:

[0135] There is and only one node in the minimum isolation range x Satisfying the above conditions, E k For the transient current energy of any node except node x E set Is a reliability coefficient, usually 1.2-1.5;

[0136] D k Is the zero sequence current direction of any node except node x

[0137] I dc_k Is the DC offset component of any node except node x I set Is the DC offset component judgment threshold.

[0138] If all the minimum isolation ranges do not satisfy the above conditions, it is a bus fault, and the node only gives an alarm.

[0139] Preferably but not limitedly, if the transient energy of the zero sequence current of the node is 4 times or more than that of other nodes, it can be considered that the transient energy of the zero sequence current of the node is much larger than that of other nodes. It can be understood that considering only 3 outages of the same length, a grounding occurs at the first end of a certain line, and the theoretical ratio is 4:1.

[0140] Preferably, the corresponding node switch tripping mode is as follows:​​​

[0141] The node near the power supply side trips, the remaining nodes in the minimum isolation range receive a "successful tripping" command or detect a loss of voltage and open, isolating the fault section; if the tripping fails, the upper adjacent node on the power supply side sends a tripping failure message, and when the node switch receives the "tripping failure" message, the node switch trips immediately if it is in the closed state.

[0142] Step 6, fault recovery, the tie switch is time-differential coordinated and delayed to close, restoring power supply to the healthy area downstream of the fault.

[0143] Preferably, the tie switch is delayed to close as follows:

[0144] When the voltage on the tie switch side is lower than the threshold, preferably but not limited to 0.8 p.u., the tie switch is delayed to close, preferably but not limited to 60 ms, to restore power supply to the healthy area downstream of the fault. When the tie switch needs to be reclosed in cooperation with the substation outgoing switch, the delay closing logic needs to be started after reclosing fails.

[0145] Embodiment 2 of the present application provides a weak communication-based single-phase ground fault positioning method for a medium-voltage power distribution network, comprising the following steps:

[0146] Based on the set sampling frequency, each node obtains real-time zero-sequence voltage and zero-sequence current sampling values;

[0147] Each node calculates the zero-sequence voltage and zero-sequence current sampling period changes based on the zero-sequence voltage and zero-sequence current sampling values;

[0148] Each node calculates the dynamic data window length according to the zero-sequence voltage sampling period changes;

[0149] According to the zero-sequence current sampling period changes, the fault component in the characteristic frequency band is extracted, and then the transient energy and current direction of the fault component in the characteristic frequency band in the dynamic data window length are calculated; and the DC offset component is calculated according to the zero-sequence current sampling period changes;

[0150] Each power distribution node is connected to adjacent power distribution nodes based on weak communication, each node interacts with any node outside the node, and based on the horizontal comparison of the fault component transient energy, current direction and DC offset component of all nodes, the minimum isolation range is identified, the node switch at the boundary of the minimum isolation range trips, and if it is determined to be a bus fault, an alarm is given;

[0151] The tie switch outside the minimum isolation range is delayed to close, restoring power supply to the healthy area downstream of the fault.

[0152] Embodiment 3 of the present application provides a single-phase ground fault section positioning system for a medium-voltage distribution network under weak communication conditions, which runs a single-phase ground fault section positioning method for a medium-voltage distribution network under weak communication conditions as described in Embodiment 1, comprising a data acquisition module, a band-pass filtering module, a feature extraction module, a fault isolation module, and a fault recovery module.

[0153] The data acquisition module is configured to acquire zero-sequence voltage and zero-sequence current analog quantities in real time at a set sampling frequency.

[0154] The band-pass filtering module is configured to calculate zero-sequence voltage period variation and zero-sequence current sampling period variation, and extract fault components in a characteristic frequency band.

[0155] The feature extraction module is configured to calculate a dynamic data window length according to the zero-sequence voltage sampling period variation, calculate a DC offset component and calculate transient energy of fault components in the characteristic frequency band and a current direction within the dynamic data window length according to the zero-sequence current sampling period variation.

[0156] The fault isolation module is configured to interact with any node outside the node, and based on the transverse comparison of transient energy of fault components, current direction, and DC offset component of all nodes, determine whether it is a bus fault, if it is a bus fault, then alarm, if it is not a bus fault, identify the minimum isolation range, and trip the node switch at the boundary of the minimum isolation range.

[0157] The fault recovery module is configured to close the tie switch outside the minimum isolation range after a delay, and restore power supply to the healthy area downstream of the fault.

[0158] Preferably, the single-phase ground fault positioning system for a medium-voltage distribution network under weak communication conditions further comprises a region division module, which is configured to divide the fault minimum isolation range with a single feeder, and establish a category and format of information interaction between nodes.

[0159] Further, the region division module establishing the category and format of information interaction between nodes comprises: storing an in-zone fault signal and an out-zone fault signal in bits 0 and 1 of the first byte, respectively, storing a tripping success signal and a tripping failure signal in bits 2 and 3 of the first byte, respectively, storing a zero-sequence current direction signal in bit 4 of the first byte, storing a DC offset overrun signal in bit 5 of the first byte, and storing transient energy of fault components of the node in the second and third bytes.

[0160] Embodiment 4 of the present application provides an electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, which, when loaded into the processor, implements the single-phase ground fault section positioning method for a medium-voltage distribution network under weak communication conditions as described in Embodiment 1.

[0161] Embodiment 5 of the present application provides a computer readable storage medium storing a computer program, the computer program, when executed by a processor, implements the method for single-phase earth fault section positioning of a medium voltage distribution network in weak communication conditions according to embodiment 1.

[0162] The present application is described with reference to the flowchart and / or block diagram of the method, device (system) and computer program product according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as a combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus generate a means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that carries out the functions specified in the flowchart and / or block diagram block or blocks.

[0163] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer readable memory produce a manufactured product including instruction apparatus, which implements the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that carries out the functions specified in the flowchart and / or block diagram block or blocks.

[0164] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable data processing apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that carries out the functions specified in the flowchart and / or block diagram block or blocks.

[0165] Although the preferred embodiments of the present application have been described, those skilled in the art who have the benefit of the present disclosure can make additional changes and modifications to these embodiments once the fundamental inventive concept is appreciated. Therefore, the appended claims are intended to be interpreted as including all the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0166] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0167] In order to more clearly introduce the outstanding substantial features of the present application and the significant progress brought to the prior art, an application example of implementing the present application is introduced below.

[0168] As shown in FIG. 2, a schematic diagram of a weak communication-based single-phase grounding fault section positioning system of a medium-voltage distribution network is shown.

[0169] The minimum isolation range of the fault section is defined as the area surrounded by the backbone line section switch and the branch / junction switch, and the branch switch and the junction switch, and the inside no longer contains switches with protection outlets. Therefore, based on the current network structure, 5 minimum isolation ranges are divided, denoted as 1#, 2#, 3#, 4# and 5#.

[0170] As shown in FIG. 3, first, consider a single-phase grounding fault of a distribution line, taking the fault of the backbone line between section switches FS1 and FS2 as an example. At this time, the fault current is the sum of the non-fault line capacitance current and the line capacitance current upstream of the fault point. From the fault point, the fault current flows to the bus through section switch FS1 and the substation outgoing line switch CB. The zero sequence current flowing through the remaining switches is only the line-to-ground capacitance current of the switch itself.

[0171] As shown in FIG. 4, there is no node in the 1#, 3#, 4# and 5# minimum isolation ranges that meets the fault section positioning judgment condition.

[0172] In the 2# minimum isolation range, node FS1 meets the fault section positioning judgment condition. Therefore, node switch FS1 near the power supply side trips, and the remaining nodes FS2, YS2, YS3 and YS4 in the fault minimum isolation range receive the trip success command or detect the loss of voltage and trip, thereby isolating the fault section.

[0173] As shown in FIG. 5, if node switch FS1 fails to trip, a “trip failure” message is sent to the upper adjacent node CB on the power supply side. Upon receiving the “trip failure” message, node CB switch trips immediately if it is in the closed state, thereby achieving fault isolation.

[0174] As shown in FIG. 6, when the tie switch LSW is below the threshold voltage (which can be 0.8 p.u.), the time difference coordination delay closing is used to restore the power supply to the healthy area 3# downstream of the fault. When the tie switch needs to be reclosed with the substation outgoing line switch, the delay closing logic needs to be started after reclosing failure.

[0175] As shown in FIG. 7, when a single-phase grounding fault occurs in the substation bus, the fault current directly flows to the bus through the fault point, and the zero sequence current flowing through all node switches is only the line-to-ground capacitance current of the switch itself.

[0176] 1#~5# Minimum isolation range, no fault section positioning research conditions meet the node, at this time, the node only fault alarm, no longer tripping.

[0177] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 means for functionally implementing the steps listed in the flowchart block or blocks.

[0178] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 function specified in the flowchart block or blocks.

[0179] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operational steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 Figure 1 steps for functionally implementing the steps listed in the flowchart block or blocks.

[0180] The embodiments of the present application are described above with reference to the drawings, but the present application is not limited to the specific embodiments described above, and the specific embodiments described above are only illustrative, not limiting, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which are all within the protection of the present application.

Claims

1. A method for locating single-phase-to-ground fault in a medium voltage distribution network based on weak communication, characterized in that, The method comprises the following steps: Each node obtains zero sequence voltage and zero sequence current sample values in real time based on a set sampling frequency; Each node calculates zero sequence voltage sample period variation and zero sequence current sample period variation based on the zero sequence voltage and zero sequence current sample values; Each node calculates a dynamic data window length according to the zero sequence voltage sample period variation; Fault components in a characteristic frequency band are extracted according to the zero sequence current sample period variation; Transient energy and current direction of the fault components in the characteristic frequency band in the dynamic data window are calculated; A direct current offset component is calculated according to the zero sequence current sample period variation; Each distribution node is connected to adjacent distribution nodes based on weak communication, each node interacts with any node outside the node, and whether the bus is faulty is determined based on transverse comparison of fault component transient energy, current direction and direct current offset component of all nodes; If the bus is faulty, an alarm is given; If the bus is not faulty, the minimum isolation range is identified, the node switch at the boundary of the minimum isolation range is tripped, and the tie switches outside the minimum isolation range are closed after a delay to restore power supply to the healthy area downstream of the fault.

2. The method according to claim 1, further comprising: dividing the fault minimum isolation range by a single feeder line. The fault minimum isolation range is the range of an area surrounded by the main line sectional switch and the branch / junction switch, and the branch switch and the junction switch, and the area does not contain switches with protection outlets.

3. The method according to claim 1, further comprising: establishing a node information interaction category and format. The 0th and 1st bits of the 1st byte store the in-zone fault signal and the out-zone fault signal, respectively, the 2nd and 3rd bits store the tripping success signal and the tripping failure signal, respectively, the 4th bit stores the zero sequence current direction signal, the 5th bit stores the direct current offset overrun signal, and the 2nd and 3rd bytes store the fault component transient energy of the node.

4. The method according to any one of claims 1 to 3, wherein the extraction of the fault components in the characteristic frequency band according to the zero sequence current sample period variation comprises: The zero sequence current sample period variation is filtered by a band-pass filter to extract the fault components in the characteristic frequency band of the band-pass filter. For a neutral point ungrounded system, the characteristic frequency band of the band-pass filter is a capacitive frequency band ranging from 0 to the first series resonance frequency of the zero sequence network. For an arc suppression coil grounded system, the characteristic frequency band of the band-pass filter is a capacitive frequency band ranging from the zero sequence line frequency band of the arc suppression coil to the first series resonance frequency of the zero sequence network.

5. The method according to claim 4, wherein the calculation of the dynamic data window length by each node according to the zero sequence voltage sample period variation comprises: ​ ​ ​ ​ Obtain the variation of zero sequence voltage sampling period of 2 cycle length before and after the single-phase ground fault time; Based on the data buffer timing, screen out the extreme point, confirm the time as t1, and take it as the starting point to screen out the first peak point time t2, and the time t1 and the time t2 are the dynamic data window length.

6. The single-phase ground fault positioning method of a medium-voltage distribution network based on weak communication according to claim 5, characterized in that: The calculation of the fault component transient energy and the current direction in the characteristic frequency band in the dynamic data window length comprises: Between the time t1 and the time t2, the fault component transient energy of each sampling point is calculated in the characteristic frequency band, and the sum is obtained to obtain the fault component transient energy in the characteristic frequency band in the dynamic data window length; The relative position of the node and the fault point is determined to determine the current direction.

7. The single-phase ground fault positioning method of a medium-voltage distribution network based on weak communication according to any one of claims 1 to 3, characterized in that: The calculation of the DC offset component according to the variation of the zero sequence current sampling period comprises: The DC offset component is taken as a parameter to construct a fitting model current expression, and the least square sum of residuals is taken as an objective to obtain the DC offset component by the nonlinear least square fitting method.

8. The single-phase ground fault positioning method of a medium-voltage distribution network based on weak communication according to any one of claims 1 to 3, characterized in that: The horizontal comparison of the fault component transient energy, the current direction and the DC offset component of all nodes to determine whether it is a bus fault comprises: The necessary and sufficient condition for fault section judgment is that the transient energy of the zero sequence current of the node is much larger than that of other nodes, or the transient energy of the zero sequence current of the node is larger than that of other nodes and is in different directions, or only the DC offset component of the zero sequence current of the node is larger than the threshold, otherwise it is a bus fault.

9. The single-phase ground fault positioning method of a medium-voltage distribution network based on weak communication according to any one of claims 1 to 3, characterized in that: The interaction between each node and any node outside the node comprises: the nodes close to the power supply side are tripped, the remaining nodes in the minimum isolation range of the fault receive the "successful tripping" command or detect the voltage loss to open, and the fault section is isolated; if the tripping fails, the upper adjacent node on the power supply side sends the tripping failure information, and the switch of the upper adjacent node on the power supply side is immediately tripped if it is in the closed state after receiving the "tripping failure" information.

10. The single-phase ground fault positioning method of a medium-voltage distribution network based on weak communication according to any one of claims 1 to 3, characterized in that: The delayed closing of the tie switch to restore power supply to the healthy area downstream of the fault comprises: When the voltage on the tie switch side is lower than the threshold, the tie switch is closed with a delay to restore power supply to the healthy area downstream of the fault; When the tie switch needs to be reclosed with the outgoing switch of the substation, the delayed closing logic needs to be started after the reclosing fails.

11. A system for locating single-phase-to-ground faults in a medium voltage distribution network based on weak communication, characterized in that Comprise: The data acquisition module, the band-pass filtering module, the feature extraction module, the fault isolation module and the fault recovery module; The data acquisition module is used to acquire zero sequence voltage and zero sequence current analog quantities in real time at a set sampling frequency. The band-pass filtering module is configured to calculate a zero-sequence voltage sampling period variation and a zero-sequence current sampling period variation, and extract a fault component in a characteristic frequency band; The feature extraction module is configured to calculate a dynamic data window length according to the zero-sequence voltage sampling period variation, calculate a DC offset component and calculate a transient energy of the fault component in the characteristic frequency band and a current direction in the dynamic data window length according to the zero-sequence current sampling period variation; The fault isolation module is configured to interact with any node outside the node, based on a transverse comparison of transient energies of fault components, current directions and DC offset components of all nodes, to determine whether a bus fault occurs, and if the bus fault occurs, to alarm, and if the bus fault does not occur, to identify a minimum isolation range and trip a node switch at a boundary of the minimum isolation range; The fault recovery module is configured to delay and close a tie switch outside the minimum isolation range to restore power supply to a healthy area downstream of the fault.

12. The weak communication based single phase to ground fault location system for medium voltage distribution network of claim 11, wherein, Further comprising: a region division module; The region division module is configured to divide a minimum fault isolation range by a single feed line, and establish a category and format of information interaction between nodes.

13. The weak communication-based single-phase ground fault locating system for a medium-voltage distribution network according to claim 12, characterized in that: The region division module establishes a category and format of information interaction between nodes, including: a 0th and 1st bit of a 1st byte store an in-zone fault signal and an out-of-zone fault signal, respectively, a 2nd and 3rd bit store a tripping success signal and a tripping failure signal, respectively, a 4th bit stores a zero-sequence current direction signal, a 5th bit stores a DC offset out-of-limit signal, and a 2nd and 3rd byte store transient energies of fault components of the node.

14. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The computer program, when loaded into the processor, implements the weak communication-based single-phase ground fault locating method for a medium-voltage distribution network according to any one of claims 1-10.

15. A computer-readable storage medium, the computer-readable storage medium storing a computer program, characterized in that, The computer program, when executed by the processor, implements the weak communication-based single-phase ground fault locating method for a medium-voltage distribution network according to any one of claims 1-10.

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