Ground fault positioning method, device and system for direct current system of transformer substation

Abstract

The invention discloses a ground fault positioning method, device and system for a substation direct current system, and relates to the technical field of direct current systems. The grounding fault positioning method for the substation direct current system comprises the following steps: acquiring branch electrical parameters of each branch in the substation direct current system, and determining a branch with a grounding fault in each branch based on bridge electrical parameters acquired by an unbalanced bridge; acquiring node parameters of each node in the branch with the grounding fault; the node parameters comprise node impedance at each node, interval impedance between two nodes, cable length between the two nodes and interval distance upper limit between the two nodes; determining a fault position point according to the node parameters of each node; obtaining the fault position probability of the fault position point; and determining the fault state of the fault position point according to the fault position probability. According to the technical scheme of the invention, by determining the fault position point and the fault position probability, accurate positioning of the fault position point in the direct current system is realized.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of direct current systems, and in particular to a method, device and system for locating a ground fault in a direct current system of a substation. Background Art

[0002] The performance of the substation DC system directly affects the operating efficiency of various equipment and devices in the entire substation, and thus has an important impact on the stability and reliability of the entire power grid.

[0003] When the insulation resistance value of the DC system grounding drops rapidly, a ground fault occurs in the DC system of the substation. At this time, it will not directly affect the normal operation of the DC system, so the protection device will not malfunction. However, if the ground fault of the DC system is not solved in time, it may cause the control circuit to fail, which in turn triggers the action of the relay protection device and eventually triggers a power outage.

[0004] At present, the wiring of the DC system of a substation is usually complicated, with a large number of branches and connection points. In addition, the frequency of grounding faults in the DC system of a substation is relatively high, and the efficiency of manual positioning and troubleshooting overlaps. Therefore, how to efficiently and accurately locate the location of the grounding fault in the DC system of a substation has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The present invention provides a method, a device and a system for locating a ground fault in a DC system of a transformer substation, so as to realize efficient and accurate positioning of a ground fault position point in the DC system of the transformer substation.

[0006] A first aspect of the present invention provides a method for locating a ground fault in a DC system of a substation. The method for locating a ground fault in a DC system of a substation comprises:

[0007] Acquire branch electrical parameters of each branch in the substation DC system and bridge electrical parameters collected based on an unbalanced bridge; wherein the unbalanced bridge is connected in series with each branch of the substation DC system;

[0008] Determine a branch having a ground fault among the branches according to the electrical parameters of the branches and the electrical parameters of the bridge;

[0009] Obtaining node parameters of each node in the branch with the ground fault; each node of the branch includes a parent node and at least one child node; the node parameters include node impedance at each node, interval impedance between the parent node and each child node, cable length between the parent node and each child node, and upper limit of interval distance between the parent node and each child node;

[0010] Determining the fault location point according to the node parameters of each of the nodes;

[0011] Obtaining a fault location probability of the fault location point;

[0012] The fault state of the fault location point is determined according to the fault location probability.

[0013] Optionally, the bridge electrical parameters collected based on the unbalanced bridge include:

[0014] A preset power supply signal is injected into the unbalanced bridge, and an output electrical signal and a bridge resistance of the unbalanced bridge are obtained as electrical parameters of the bridge.

[0015] Optionally, determining a branch having a ground fault among the branches according to the electrical parameters of the branches and the electrical parameters of the bridge includes:

[0016] Determining the grounding resistance of each branch circuit respectively according to the electrical parameters of each branch circuit and the electrical parameters of the bridge circuit;

[0017] The branch whose grounding resistance is not within the preset resistance range is determined as a branch with a grounding fault.

[0018] Optionally, determining the fault location point according to the node parameters of each of the nodes includes:

[0019] According to the node parameters of each of the nodes, the fault distance d is determined based on a second calculation formula; the second calculation formula is:

[0020]

[0021] Among them, φ up is the impedance of the parent node, φ dn is the impedance of the subnode, d up is the upper limit of the interval distance between the parent node and the child node, L sec is the cable length between the parent node and the child node, Δφ is the impedance between the parent node and the child node and the impedance of the parent node φ up The difference between

[0022] The fault location point is determined according to the distance between the fault point and the grounding point.

[0023] Optionally, obtaining the fault location probability of the fault location point includes:

[0024] Obtaining the fault occurrence probability and the fault warning probability of the fault location point;

[0025] According to the fault occurrence probability and the fault warning probability, the fault location probability of the fault location point is determined based on an improved Bayesian network model; the improved Bayesian network model is:

[0026]

[0027] Among them, p(gj) is the probability of the fault occurrence, p(wi|gj) is the fault warning probability, p(wi|kj) is the fault location probability, gj is a suspected fault, and Fm is the set of fault location points.

[0028] Optionally, obtaining the fault occurrence probability and the fault warning probability of the fault location point includes:

[0029] Obtaining the total number of faults of the DC system of the substation, the number of faults occurring at the fault location, and the number of fault warnings at the fault location;

[0030] Determining the probability of the fault occurring according to the number of fault occurrences and the total number of faults;

[0031] The fault warning probability is determined according to the number of fault warnings and the number of fault occurrences.

[0032] Optionally, determining the fault state of the fault location point according to the fault location probability includes:

[0033] Determining whether the fault location probability is greater than or equal to a preset probability;

[0034] If so, it is determined that the fault location point is a grounding fault point.

[0035] Optionally, the method for locating a ground fault in a DC system of a substation further includes:

[0036] The wireless communication module is controlled to send the location information of the ground fault point to the remote terminal.

[0037] A second aspect of the present invention provides a ground fault locating device for a DC system of a substation, the ground fault locating device for a DC system of a substation comprising:

[0038] An electrical parameter acquisition module, used to acquire branch electrical parameters of each branch in the substation DC system and bridge electrical parameters acquired based on an unbalanced bridge; wherein the unbalanced bridge is connected in series with each branch of the substation DC system;

[0039] A fault branch determination module, used to determine a branch with a ground fault among the branches according to the electrical parameters of the branches and the electrical parameters of the bridge;

[0040] A node parameter acquisition module, used to acquire node parameters of each node in the branch with the ground fault; each node of the branch includes a parent node and at least one child node; the node parameters include node impedance at each node, interval impedance between the parent node and each child node, cable length between the parent node and each child node, and upper limit of interval distance between the parent node and each child node;

[0041] A fault location determination module, used to determine the fault location point according to the node parameters of each of the nodes;

[0042] A fault probability acquisition module, used to acquire the fault location probability of the fault location point;

[0043] A fault state determination module is used to determine the fault state of the fault location point according to the fault location probability.

[0044] A third aspect of the present invention provides a ground fault location system for a substation DC system. The ground fault location system for a substation DC system comprises:

[0045] Impedance measurement module, control module and wireless communication module;

[0046] The impedance measurement module is used to obtain the operating conditions of the DC system of the substation;

[0047] The control module is connected to the impedance measurement module and the wireless communication module respectively, and the control module is used to execute the ground fault location method of the substation DC system as described above.

[0048] The embodiment of the present invention determines the branch with a grounding fault in each branch by acquiring the branch electrical parameters of each branch in the substation DC system and the bridge electrical parameters collected based on the unbalanced bridge connected in series with each branch of the substation DC system, thereby accurately determining the branch with a grounding fault and improving the efficiency of the grounding fault locating system of the substation DC system; at the same time, by acquiring the node parameters of each node in the branch with a grounding fault, the fault location point in the branch with a grounding fault can be located according to the node parameters of each node in the branch with a grounding fault, and by acquiring the fault location probability of the fault location point, the fault state of the fault location point can be determined, thereby evaluating the fault possibility of the fault location point, improving the accuracy of locating the fault location point in the fault branch, and thus improving the reliability and safety of the substation DC system.

[0049] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 It is a flow chart of a method for locating a ground fault in a DC system of a substation provided in Embodiment 1 of the present invention;

[0052] Figure 2 This is a schematic diagram of a circuit structure of a DC system of a substation provided by Embodiment 1 of the present invention;

[0053] Figure 3 is a structural schematic diagram of an unbalanced bridge provided by Embodiment 1 of the present invention;

[0054] Figure 4 It is a flow chart of a method for locating a ground fault in a DC system of a substation provided by a second embodiment of the present invention;

[0055] Figure 5 It is a flow chart of a method for locating a ground fault in a DC system of a substation provided by a third embodiment of the present invention;

[0056] Figure 6 It is a flow chart of a method for locating a ground fault in a DC system of a substation provided by a fourth embodiment of the present invention;

[0057] Figure 7 It is a structural schematic diagram of a ground fault locating device for a DC system of a substation provided by Embodiment 5 of the present invention;

[0058] Figure 8 It is a structural schematic diagram of a ground fault location system of a substation DC system provided in Embodiment 6 of the present invention. DETAILED DESCRIPTION

[0059] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0060] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0061] Embodiment 1

[0062] Figure 1 This is a flow chart of a method for locating a ground fault in a DC system of a substation provided by the first embodiment of the present invention. This embodiment is applicable to locating a ground fault point in a DC system of a substation. The method can be performed by a ground fault locating device for a DC system of a substation. The device can be implemented by software and / or hardware and can generally be integrated in a control module of a ground fault locating system for a DC system of a substation. Figure 1 As shown, the ground fault location method of the substation DC system may include:

[0063] S101, acquiring branch electrical parameters of each branch in a DC system of a substation and bridge electrical parameters acquired based on an unbalanced bridge.

[0064] Among them, the unbalanced bridge is connected in series with each branch of the DC system of the substation, for example, Figure 2 As shown, the DC system of the substation includes a bus positive pole 01, a bus negative pole 02, and multiple branches, multiple branches (1, 2, ..., M). The bridge electrical parameters can be specifically understood as the output current, output voltage, and bridge resistance of the unbalanced bridge, and the branch electrical parameters of each branch can be specifically understood as the branch current, branch voltage, and branch impedance of each branch.

[0065] Specifically, the branch current value of each branch and the output current of the unbalanced bridge are obtained through a current sensor or a current transformer, and the voltage value of each branch and the output voltage of the unbalanced bridge are obtained through a voltage sensor or a voltage transformer. The branch impedance value of each branch can be calculated through the branch current value of each branch and the branch voltage value of each branch; the bridge resistance of the unbalanced bridge can be a fixed resistance, which can be directly stored in a corresponding memory, and the bridge resistance can be directly called from the memory when needed.

[0066] In an optional embodiment, the bridge electrical parameters collected based on the unbalanced bridge include: injecting a preset power supply signal into the unbalanced bridge, and acquiring the output electrical signal and bridge resistance of the unbalanced bridge as the bridge electrical parameters.

[0067] Among them, Figure 3 As shown, the bridge can be specifically understood as a circuit structure composed of four resistors, usually composed of four resistors, including a first resistor R11, a second resistor R12, a third resistor R13 and a fourth resistor R14, wherein the first resistor R11 and the third resistor R13 are connected in series, the second resistor R12 and the fourth resistor R14 are connected in series, and the two groups of series resistors are connected in parallel. In an unbalanced bridge, the resistance values ​​of the four resistors may not be equal, so that the output voltage of the bridge is not zero when the bridge is in an unbalanced state.

[0068] For details, please refer to Figure 2 The unbalanced bridge 4 is connected in series with each branch of the substation DC system, a preset power supply signal is introduced into the unbalanced bridge 4, and the output current and output voltage of the output end of the unbalanced bridge 4 are measured respectively by a current sensor and a voltage sensor, and the output current, output voltage and bridge resistance value of the unbalanced bridge are determined as bridge electrical parameters, so that the overall resistance value of the substation DC system can be determined through the bridge resistance, output current and output voltage.

[0069] S102: Determine a branch with a ground fault among the branches according to electrical parameters of the branches and electrical parameters of the bridge.

[0070] Specifically, the overall resistance value of the substation DC system can be determined based on the output current and output voltage of the unbalanced bridge, and whether there is a faulty branch in the substation DC system can be determined based on the overall resistance value. For example, the overall resistance value of the substation DC system can be compared with a set resistance range. When the overall resistance value of the substation DC system is within the set resistance range, it can be determined that there is no faulty branch in the substation DC system; and when the overall resistance value of the substation DC system is not within the set resistance range, it can be determined that there is a faulty branch in the substation DC system. At this time, the overall resistance value of each branch and the unbalanced bridge can be further determined. The bridge resistance and the branch voltage of each branch can be used to determine the voltage of each branch to ground. Then, according to the voltage to ground of the branch and the branch current of the branch, the grounding resistance of the branch can be determined. By judging whether the grounding resistance value of the branch is within the preset range of normal grounding resistance values, it can be further determined whether there is a grounding fault in the branch. That is, the branch whose grounding resistance value is not within the preset range of normal grounding resistance values ​​can be determined as a branch with a grounding fault. The branch with a grounding fault can be accurately determined, thereby improving the efficiency of the grounding fault locating system of the substation DC system and improving the accuracy of locating the grounding fault position point in the substation DC system.

[0071] S103: Obtain node parameters of each node in the branch with the ground fault.

[0072] Among them, the nodes of each branch include a parent node and at least one child node; the node parameters include the node impedance at each node, the interval impedance between the parent node and each child node, the cable length between the parent node and each child node, and the upper limit of the interval distance between the parent node and each child node.

[0073] Specifically, a node in a branch can be understood as a device connection point in the branch, a parent node in a node can be understood as a connection point of a key device in the branch, and a child node in a node can be understood as a connection point of other devices in the branch for assisting the key device to work. For example, Figure 2 As shown, if the branch with a ground fault is branch 1, branch 1 includes switch 001, key device 002 and switch 003, wherein the connection point of key device 002 is the parent node of the branch, and the connection point of switch 001 and switch 003 is the child node of the branch. The node impedance at the node can be specifically understood to include the resistance and reactance at the node; the interval impedance between the parent node and the child node can be specifically understood to be the resistance and reactance between the parent node and the child node; the cable length between the parent node and the child node can be specifically understood to be the actual length of the cable connecting the child node and the parent node; the upper limit of the interval distance between the parent node and the child node can be specifically understood to be the maximum distance limit between the parent node and the child node.

[0074] S104: Determine the fault location point according to the node parameters of each node.

[0075] Specifically, according to the node impedance at each node, the interval impedance between the child node and the parent node, the cable length between the child node and the parent node, and the upper limit of the interval distance between the child node and the parent node, the distance between the parent node and the faulty child node can be determined, so that the fault location point in each child node can be determined according to the distance, so that the specific fault location point in the branch with the grounding fault can be accurately determined, which helps to quickly and accurately repair the grounding fault in the substation DC system and ensure the continuous and stable operation of the substation DC system.

[0076] S105. Obtain the fault location probability of the fault location point.

[0077] Among them, the fault location probability of the fault location point can be specifically understood as the probability of a fault occurring at the fault location point. By determining the probability of a fault occurring at the fault location point, the misjudgment of the fault location point due to power grid fluctuations in the substation is avoided, so that the possibility of a fault at the fault location point can be more comprehensively evaluated, and the accuracy of locating the fault location point in the fault branch is improved.

[0078] S106. Determine the fault state of the fault location point according to the fault location probability.

[0079] Specifically, the probability of a fault at the fault location point is compared with a preset probability. When the probability of a fault at the fault location point is greater than or equal to the preset probability, it can be determined that a fault exists at the fault location point. When the probability of a fault at the fault location point is less than the preset probability, it is considered that there is a misjudgment of the fault state of the fault location point, and the fault location point in the fault branch should be relocated. The fault state of the fault location point is determined by the fault location probability, which improves the accuracy of locating the fault location point in the fault branch, thereby improving the reliability and safety of the substation DC system.

[0080] In an optional embodiment, determining the fault state of the fault location point according to the fault location probability may include: judging whether the fault location probability is greater than or equal to a preset probability; if so, determining that the fault location point is a grounding fault point.

[0081] The preset probability may be specifically understood as a probability value set in advance under specific conditions, which is used as a reference standard or threshold for determining whether the fault location point is a ground fault point. Exemplarily, the preset probability may be 90%.

[0082] Specifically, after determining the fault location probability of the fault location point, the fault location probability of the fault location point is compared with the preset probability. When the fault location probability of the fault location point is greater than or equal to the preset probability, it can be determined that a fault exists at the fault location point. When the fault location probability of the fault location point is less than the preset probability, it is considered that there is a misjudgment of the fault state of the fault location point, and the fault location point in the fault branch should be relocated, thereby improving the accuracy of locating the fault location point in the fault branch.

[0083] In this embodiment, the branch electrical parameters of each branch in the substation DC system and the bridge electrical parameters collected based on the unbalanced bridge connected in series with each branch of the substation DC system are obtained to determine the branch with the grounding fault in each branch, so that the branch with the grounding fault can be accurately determined, thereby improving the efficiency of the grounding fault positioning system of the substation DC system; at the same time, by obtaining the node parameters at each node in the branch with the grounding fault, the fault location point in the branch with the grounding fault can be located according to the node parameters of each node in the branch with the grounding fault, thereby accurately locating the fault location point in the branch with the grounding fault, and by obtaining the fault location probability of the fault location point to determine the fault state of the fault location point, thereby being able to more comprehensively evaluate the fault possibility of the fault location point, improving the accuracy of locating the fault location point in the fault branch, thereby improving the reliability and safety of the substation DC system.

[0084] Embodiment 2

[0085] Figure 4 is a flow chart of a method for locating a ground fault in a DC system of a substation provided in a second embodiment of the present invention. Based on the above embodiment, this embodiment describes in detail a method for determining a branch having a ground fault in each branch. Accordingly, Figure 4 As shown, the ground fault location method of the DC system of the substation may include:

[0086] S201, acquiring branch electrical parameters of each branch in a DC system of a substation and bridge electrical parameters acquired based on an unbalanced bridge.

[0087] S202: Determine the grounding resistance of each branch according to the electrical parameters of each branch and the electrical parameters of the bridge.

[0088] Specifically, the electrical parameters of the bridge may include the output current, output voltage and bridge resistance of the unbalanced bridge. According to the output current and output voltage of the unbalanced bridge, it can be determined whether there is a faulty branch in the branches of the substation DC system. For example, the overall resistance of the substation DC system can be calculated according to the output current and output voltage of the unbalanced bridge, and it can be judged whether the overall resistance is within the set resistance range. When the overall resistance is not within the set resistance range, the voltage to ground of each branch can be further calculated. Specifically, the voltage to ground of the branch can be determined according to the bridge resistance value of the unbalanced bridge, the insulation resistance of the positive and negative busbars to ground, and the branch voltage of the branch. Then, according to the branch current of the branch, the grounding resistance of each branch can be calculated accordingly.

[0089] In an optional embodiment, the voltage of the branch to ground can be calculated using the following formula:

[0090]

[0091] Among them, R a is the insulation resistance of the positive and negative busbars to the ground, R2 and R J is the bridge resistance of the unbalanced bridge, V + is the voltage of the branch to ground, V is the branch voltage of the branch, and V can also be understood as the voltage at the beginning of the branch.

[0092] S203: Determine a branch whose grounding resistance is not within a preset resistance range as a branch with a grounding fault.

[0093] Among them, the preset resistance range can be specifically understood as the range of normal values ​​of grounding resistance. When the DC system of the substation is working normally, the value of the grounding resistance will fluctuate within the preset resistance range. The value of the grounding resistance exceeds the preset range, indicating that there is a grounding fault in the DC system of the substation. The preset resistance range can be set according to past experience and rules.

[0094] Specifically, by judging whether the grounding resistance value of each branch is within a preset resistance range, the branch whose grounding resistance value is not within the preset range of normal grounding resistance value is determined as a branch with a grounding fault. At the same time, the branch whose grounding resistance value is within the preset range of normal grounding resistance value is determined as a branch without a grounding fault. In this way, it is possible to more effectively judge whether each branch has a grounding fault through the grounding resistance of each branch, thereby improving the accuracy of locating the fault position point in the faulty branch and at the same time improving the efficiency of the grounding fault locating system of the substation DC system.

[0095] S204: Obtain node parameters of each node in the branch with the ground fault.

[0096] S205: Determine the fault location point according to the node parameters of each node.

[0097] S206: Obtain the fault location probability of the fault location point.

[0098] S207: Determine the fault state of the fault location point according to the fault location probability.

[0099] In this embodiment, the grounding resistance of each branch is determined respectively according to the electrical parameters of each branch and the electrical parameters of the bridge, and the branch whose grounding resistance is not within the preset resistance range is determined as the branch with the grounding fault. Through the preset resistance range, it is possible to more effectively judge whether each branch has a grounding fault through the grounding resistance of each branch, thereby accurately determining the branch with the grounding fault in the substation DC system, improving the accuracy of locating the fault position point in the faulty branch, and at the same time improving the efficiency of the grounding fault locating system of the substation DC system.

[0100] Embodiment 3

[0101] Figure 5 is a flow chart of a method for locating a ground fault in a DC system of a substation provided in the third embodiment of the present invention. Based on the above embodiment, this embodiment describes in detail the method for determining a fault location point and obtaining the fault location probability of a fault location point according to the node parameters of each node. Figure 5 As shown, the ground fault location method of the DC system of the substation may include:

[0102] S301, acquiring branch electrical parameters of each branch in the DC system of the substation and bridge electrical parameters collected based on an unbalanced bridge.

[0103] S302: Determine a branch with a ground fault among the branches according to electrical parameters of the branches and electrical parameters of the bridge.

[0104] S303: Obtain node parameters of each node in the branch with the ground fault.

[0105] S304: Determine the fault distance according to the node parameters of each node based on a second calculation formula.

[0106] Among them, the second calculation formula is:

[0107]

[0108] Among them, φ up is the impedance of the parent node, φ dn is the impedance of the child node, d up is the upper limit of the interval distance between the parent node and the child node, L secis the cable length between the parent node and the child node, Δφ is the impedance between the parent node and the child node and the impedance of the parent node φ up The difference between .

[0109] Specifically, since the grounding resistance of the branch with the grounding fault is not within the preset resistance range, it can be determined that a fault occurs at a node in the branch with the grounding fault. At this time, each node in the branch with the grounding fault can be checked separately, and the relative distance between each child node and the parent node can be calculated by substituting the impedance parameter and distance parameter of each node into the second calculation formula. The relative distance between the child node and the parent node is compared with the upper limit of the interval distance between the child node and the parent node, and the relative distance corresponding to the child node with an abnormal comparison result is determined as the fault distance.

[0110] S305: Determine the fault location point according to the fault distance.

[0111] Specifically, after the fault distance is determined, the faulty child node can be correspondingly determined according to the position of the parent node itself and the positions of each child node, and the position of the faulty child node is determined as the fault location point.

[0112] S306: Obtain the fault occurrence probability and the fault warning probability of the fault location point.

[0113] The fault occurrence probability of the fault location point can be specifically understood as the ratio of the number of fault occurrences at the fault location point to the total number of faults in the substation DC system, and the fault warning probability can be specifically understood as the ratio of the number of fault warnings at the fault location point to the number of fault occurrences at the fault location point.

[0114] In an optional embodiment, the fault occurrence probability and the fault warning probability of the fault location point are obtained, including: obtaining the total number of faults in the substation DC system, the number of fault occurrences at the fault location point, and the number of fault warnings at the fault location point; determining the fault occurrence probability based on the number of fault occurrences and the total number of faults; determining the fault warning probability based on the number of fault warnings and the number of fault occurrences.

[0115] Among them, the probability of failure occurrence p(g j ) can be calculated based on the following formula:

[0116]

[0117] Among them, n(g j ) is the number of fault occurrences at the fault location, and n(g) is the total number of faults in the substation DC system.

[0118] Fault warning probability p(w i ∣g j) can be calculated based on the following formula:

[0119]

[0120] Among them, n(g k ) is the number of fault warnings at the fault location, n(g j ) is the number of fault occurrences at the fault location.

[0121] S307. According to the fault occurrence probability and the fault warning probability, based on the improved Bayesian network model, determine the fault location probability of the fault location point.

[0122] Among them, the improved Bayesian network model is:

[0123]

[0124] Among them, p(gj) is the probability of fault occurrence, p(wi|gj) is the probability of fault warning, p(wi|kj) is the probability of fault location, gj is the suspected fault, and Fm is the set of fault location points.

[0125] Among them, the Bayesian network model can be specifically understood as a probabilistic graph model, which is used to describe the probabilistic dependency relationship between different variables. Specifically, according to the calculated fault occurrence probability and fault warning probability, based on the improved Bayesian network model, the relationship between the fault warning and the actual occurrence probability of the fault location point can be determined, thereby calculating the fault location probability. After determining the fault location probability of the fault location point, the fault location probability can be compared with the preset probability. When the fault location probability of the fault location point is greater than or equal to the preset probability, it can be determined that there is a fault at the fault location point. When the fault location probability of the fault location point is less than the preset probability, it is considered that the fault state of the fault location point is misjudged, and the fault location point in the fault branch should be relocated, thereby achieving accurate positioning of the fault location point in the branch with a grounding fault.

[0126] S308. Determine the fault state of the fault location point according to the fault location probability.

[0127] In this embodiment, the fault distance is determined according to the node parameters of each node, and the fault location point is determined according to the fault distance, so that the fault location point in the branch with the grounding fault can be accurately located; at the same time, by obtaining the fault occurrence probability and the fault warning probability of the fault location point, and based on the improved Bayesian network model, the fault location probability of the fault location point is determined. When the fault location probability of the fault location point is greater than or equal to the preset probability, it can be determined that the fault location point has a fault, so that the fault possibility of the fault location point can be more comprehensively evaluated, thereby realizing the accurate positioning of the fault location point in the branch with the grounding fault.

[0128] Embodiment 4

[0129] Figure 6 is a flow chart of a method for locating a ground fault in a DC system of a substation provided by a fourth embodiment of the present invention. Based on the above embodiments, this embodiment describes in detail a method for determining a fault state of a fault location point according to a fault location probability and a post-processing method after determining the fault location point. Accordingly, Figure 6 As shown, the ground fault location method of the DC system of the substation may include:

[0130] S401, acquiring branch electrical parameters of each branch in the DC system of the substation and bridge electrical parameters collected based on an unbalanced bridge.

[0131] S402: Determine a branch with a ground fault among the branches according to electrical parameters of the branches and electrical parameters of the bridge.

[0132] S403: Obtain node parameters of each node in the branch with the ground fault.

[0133] S404: Determine the fault location point according to the node parameters of each node.

[0134] S405: Obtain the fault location probability of the fault location point.

[0135] S406: Determine the fault state of the fault location point according to the fault location probability.

[0136] S407: Control the wireless communication module to send the location information of the grounding fault point to the remote terminal.

[0137] Specifically, after determining the ground fault point, the wireless communication module can be controlled to send the location information of the ground fault point to the remote terminal to inform the operation and maintenance personnel that there is a ground fault in the DC system of the substation and the location information of the ground fault point, and that the ground fault location point needs to be repaired, so that the ground fault in the DC system of the substation can be repaired quickly and accurately, ensuring the continuous and stable operation of the DC system of the substation. Among them, the method of sending the location information of the ground fault point may include but is not limited to e-mail, text message, or other remote notifications. On the premise that the operation and maintenance personnel can be informed that there is a ground fault in the DC system of the substation and the location information of the ground fault point, and that the ground fault location point needs to be repaired, the embodiment of the present invention does not specifically limit this.

[0138] In this embodiment, the wireless communication module is controlled to send the location information of the grounding fault point to the remote terminal to inform the operation and maintenance personnel that there is a grounding fault in the DC system of the substation and the location information of the grounding fault point, and the grounding fault location point needs to be inspected and repaired, so that the grounding fault in the DC system of the substation can be repaired quickly and accurately, ensuring the continuous and stable operation of the DC system of the substation.

[0139] Embodiment 5

[0140] Figure 7 This is a schematic diagram of the structure of a ground fault location device for a substation DC system provided in Embodiment 5 of the present invention. The device can implement the ground fault location method for a substation DC system provided in the embodiment of the present invention. The device can be implemented by software and / or hardware, and can generally be integrated in the control module of the ground fault location system for the substation DC system. Figure 7 As shown, the device comprises:

[0141] The electrical parameter acquisition module 501 is used to acquire branch electrical parameters of each branch in the DC system of the substation and bridge electrical parameters collected based on an unbalanced bridge.

[0142] Among them, the unbalanced bridge is connected in series with each branch of the substation DC system.

[0143] The faulty branch determining module 502 is used to determine the branch with the ground fault among the branches according to the electrical parameters of the branches and the electrical parameters of the bridge.

[0144] The node parameter acquisition module 503 is used to acquire the node parameters of each node in the branch with the ground fault.

[0145] Among them, the nodes of each branch include a parent node and at least one child node; the node parameters include the node impedance at each node, the interval impedance between the parent node and each child node, the cable length between the parent node and each child node, and the upper limit of the interval distance between the parent node and each child node.

[0146] The fault location determination module 504 is used to determine the fault location point according to the node parameters of each node.

[0147] The fault probability acquisition module 505 is used to acquire the fault location probability of the fault location point.

[0148] The fault state determination module 506 is used to determine the fault state of the fault location point according to the fault location probability.

[0149] In an optional embodiment of the present invention, the electrical parameter acquisition module 501 may also be used to: inject a preset power supply signal into the unbalanced bridge, and acquire the output electrical signal and bridge resistance of the unbalanced bridge as electrical parameters of the bridge.

[0150] In one embodiment of the present invention, the fault branch determination module 502 can also be used to: determine the grounding resistance of each branch according to the electrical parameters of each branch and the electrical parameters of the bridge; and determine the branch whose grounding resistance is not within the preset resistance range as a branch with a grounding fault.

[0151] In one embodiment of the present invention, the fault location determination module 504 may also be used to: determine the fault distance d according to the node parameters of each node based on the second calculation formula; and determine the fault location point according to the fault distance.

[0152] Among them, the second calculation formula is:

[0153]

[0154] in, is the impedance of the parent node, is the impedance of the child node, d up is the upper limit of the interval distance between the parent node and the child node, L sec is the cable length between the parent node and the child node, The impedance between the parent node and the child node and the impedance of the parent node The difference.

[0155] In one embodiment of the present invention, the fault probability acquisition module 505 can also be used to: obtain the fault occurrence probability and the fault warning probability of the fault location point; determine the fault location probability of the fault location point based on the improved Bayesian network model according to the fault occurrence probability and the fault warning probability.

[0156] Among them, the improved Bayesian network model is:

[0157]

[0158] Among them, p(gj) is the probability of fault occurrence, p(wi|gj) is the probability of fault warning, p(wi|kj) is the probability of fault location, gj is the suspected fault, and Fm is the set of fault location points.

[0159] In one embodiment of the present invention, the fault probability acquisition module 505 can also be used to: obtain the total number of faults in the substation DC system, the number of faults occurring at the fault location point, and the number of fault warnings at the fault location point; determine the probability of fault occurrence based on the number of faults occurring and the total number of faults; determine the probability of fault warning based on the number of fault warnings and the number of faults occurring.

[0160] In one embodiment of the present invention, the fault state determination module 506 may also be used to: determine whether the fault location probability is greater than or equal to a preset probability; if so, determine that the fault location point is a grounding fault point.

[0161] In one embodiment of the present invention, the fault state determination module 506 may also be used to: control the wireless communication module to send the location information of the ground fault point to the remote terminal.

[0162] The above-mentioned ground fault location device of the substation DC system can execute the ground fault location method of the substation DC system provided by any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method. For technical details not described in detail in this embodiment, please refer to the ground fault location method of the substation DC system provided by any embodiment of the present invention.

[0163] Since the ground fault locating device of the substation DC system introduced above is a device that can execute the ground fault locating method of the substation DC system in the embodiment of the present invention, based on the ground fault locating method of the substation DC system introduced in the embodiment of the present invention, the technical personnel in this field can understand the specific implementation mode and various variations of the ground fault locating device of the substation DC system of this embodiment, so how the ground fault locating device of the substation DC system implements the ground fault locating method of the substation DC system in the embodiment of the present invention is not described in detail here. As long as the technical personnel in this field implement the device used by the ground fault locating method of the substation DC system in the embodiment of the present invention, it belongs to the scope of protection of this application.

[0164] Embodiment 6

[0165] Figure 8 : is a structural diagram of a ground fault location system of a substation DC system provided in Embodiment 6 of the present invention. The ground fault location system of the substation DC system can implement the ground fault location method of the substation DC system provided in the embodiment of the present invention. Figure 8 As shown, the ground fault location system of the power station DC system includes: an impedance measurement module 10, a control module 20 and a wireless communication module 30;

[0166] The impedance measurement module 10 is used to obtain the operating conditions of the DC system of the substation;

[0167] The control module 20 is connected to the impedance measurement module 10 and the wireless communication module 30 respectively, and the control module 20 is used to execute the ground fault location method of the substation DC system provided by any of the above embodiments.

[0168] The above-mentioned ground fault location system of the substation DC system can execute the ground fault location method of the substation DC system provided by any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method. For technical details not described in detail in this embodiment, please refer to the ground fault location method of the substation DC system provided by any embodiment of the present invention.

[0169] Since the ground fault location system of the substation DC system introduced above is a system that can execute the ground fault location method of the substation DC system in the embodiment of the present invention, based on the ground fault location method of the substation DC system introduced in the embodiment of the present invention, the technical personnel in this field can understand the specific implementation mode and various variations of the ground fault location system of the substation DC system of this embodiment, so how the ground fault location system of the substation DC system implements the ground fault location method of the substation DC system in the embodiment of the present invention is not introduced in detail here. As long as the technical personnel in this field implement the system adopted by the ground fault location method of the substation DC system in the embodiment of the present invention, it belongs to the scope of protection of this application.

[0170] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0171] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for locating a ground fault in a DC system of a substation, characterized in that: include: Acquire branch electrical parameters of each branch in the substation DC system and bridge electrical parameters collected based on an unbalanced bridge; wherein the unbalanced bridge is connected in series with each branch of the substation DC system; Determine a branch having a ground fault among the branches according to the electrical parameters of the branches and the electrical parameters of the bridge; Obtaining node parameters of each node in the branch with the ground fault; each node of the branch includes a parent node and at least one child node; the node parameters include node impedance at each node, interval impedance between the parent node and each child node, cable length between the parent node and each child node, and upper limit of interval distance between the parent node and each child node; Determining the fault location point according to the node parameters of each of the nodes; Obtaining a fault location probability of the fault location point; The fault state of the fault location point is determined according to the fault location probability.

2. The method for locating a ground fault in a DC system of a substation according to claim 1, characterized in that: The bridge electrical parameters collected based on the unbalanced bridge include: A preset power supply signal is injected into the unbalanced bridge, and an output electrical signal and a bridge resistance of the unbalanced bridge are obtained as electrical parameters of the bridge.

3. The method for locating a ground fault in a DC system of a substation according to claim 1, characterized in that: Determining a branch having a ground fault among the branches according to the electrical parameters of the branches and the electrical parameters of the bridge includes: Determining the grounding resistance of each branch circuit respectively according to the electrical parameters of each branch circuit and the electrical parameters of the bridge circuit; The branch whose grounding resistance is not within the preset resistance range is determined as a branch with a grounding fault.

4. The method for locating a ground fault in a DC system of a substation according to claim 1, characterized in that: Determining the fault location point according to the node parameters of each of the nodes includes: According to the node parameters of each of the nodes, the fault distance d is determined based on a second calculation formula; the second calculation formula is: Among them, φ up is the impedance of the parent node, φ dn is the impedance of the subnode, d up is the upper limit of the interval distance between the parent node and the child node, L sec is the cable length between the parent node and the child node, Δφ is the impedance between the parent node and the child node and the impedance of the parent node φ up The difference between The fault location point is determined according to the fault distance.

5. The method for locating ground faults in a DC system of a substation according to claim 1, characterized in that: Obtaining the fault location probability of the fault location point includes: Obtaining the fault occurrence probability and the fault warning probability of the fault location point; According to the fault occurrence probability and the fault warning probability, the fault location probability of the fault location point is determined based on an improved Bayesian network model; the improved Bayesian network model is: Among them, p(gj) is the probability of the fault occurrence, p(wi|gj) is the fault warning probability, p(wi|kj) is the fault location probability, gj is a suspected fault, and Fm is the set of fault location points.

6. The method for locating ground faults in a DC system of a substation according to claim 5, characterized in that: Obtaining the fault occurrence probability and the fault warning probability of the fault location point includes: Obtaining the total number of faults of the DC system of the substation, the number of faults occurring at the fault location, and the number of fault warnings at the fault location; Determining the probability of the fault occurring according to the number of fault occurrences and the total number of faults; The fault warning probability is determined according to the number of fault warnings and the number of fault occurrences.

7. The method for locating ground faults in a DC system of a substation according to claim 1, characterized in that: Determining the fault state of the fault location point according to the fault location probability includes: Determining whether the fault location probability is greater than or equal to a preset probability; If so, it is determined that the fault location point is a grounding fault point.

8. The method for locating ground faults in a DC system of a substation according to claim 7, characterized in that: Also includes: The wireless communication module is controlled to send the location information of the ground fault point to the remote terminal.

9. A ground fault location device for a DC system of a substation, characterized in that: include: An electrical parameter acquisition module, used to acquire branch electrical parameters of each branch in the substation DC system and bridge electrical parameters acquired based on an unbalanced bridge; wherein the unbalanced bridge is connected in series with each branch of the substation DC system; A fault branch determination module, used to determine a branch with a ground fault among the branches according to the electrical parameters of the branches and the electrical parameters of the bridge; A node parameter acquisition module, used to acquire node parameters of each node in the branch with ground fault; each node of the branch includes a parent node and at least one child node; the node parameters include node impedance at each node, interval impedance between the parent node and each child node, cable length between the parent node and each child node, and upper limit of interval distance between two nodes; A fault location determination module, used to determine the fault location point according to the node parameters of each of the nodes; A fault probability acquisition module, used to acquire the fault location probability of the fault location point; A fault state determination module is used to determine the fault state of the fault location point according to the fault location probability.

10. A ground fault location system for a substation DC system, characterized in that: include: Impedance measurement module, control module and wireless communication module; The impedance measurement module is used to obtain the operating conditions of the DC system of the substation; The control module is connected to the impedance measurement module and the wireless communication module respectively, and the control module is used to execute the ground fault locating method of the substation DC system according to any one of claims 1-8.

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