A method, device and system for locating a ground fault of a substation DC system

Abstract

The application discloses a substation DC system grounding fault positioning method, device and system, and relates to the technical field of DC systems. The substation DC system grounding fault positioning method comprises the following steps: acquiring branch electric parameters of each branch in a substation DC system and electric bridge electric parameters collected based on an unbalanced electric bridge, and determining a branch in which a grounding fault exists; acquiring node parameters of each node in the branch in which the grounding fault exists; the node parameters comprise node impedance at each node, interval impedance between two nodes, cable length between the two nodes, and an upper limit of interval distance between the two nodes; determining a fault position point according to the node parameters of each node; acquiring a fault position probability of the fault position point; and determining a fault state of the fault position point according to the fault position probability. The technical scheme of the application realizes accurate positioning of a fault position point in a DC system by determining the fault position point and the fault position probability.

Description

TECHNICAL FIELD

[0001] The embodiment of the application relates to the technical field of direct current systems, in particular to a grounding fault positioning method, device and system for a substation direct current system. BACKGROUND

[0002] The performance of the substation direct current system directly affects the operation efficiency of various devices and apparatuses in the entire substation, and further has an important influence on the stability and reliability of the entire power grid.

[0003] When the insulation resistance value of the grounding of the direct current system rapidly decreases, the grounding fault of the substation direct current system occurs, at this time, the normal operation of the direct current system is not directly affected, so the protection device will not malfunction. However, if the grounding fault of the direct current system is not solved in time, the control loop may fail, thereby causing the action of the relay protection device, and finally triggering the power failure accident.

[0004] At present, the wiring of the substation direct current system is usually relatively complex, there are a large number of branches and connection points, and the frequency of the grounding fault of the substation direct current system is relatively high, and the manual positioning and troubleshooting efficiency is overlapped, therefore, how to efficiently and accurately position the grounding fault position point in the substation direct current system becomes a technical problem to be solved at present. SUMMARY

[0005] The application provides a grounding fault positioning method, device and system for a substation direct current system, to efficiently and accurately position the grounding fault position point in the substation direct current system.

[0006] The application provides a grounding fault positioning method for a substation direct current system, the grounding fault positioning method for the substation direct current system comprising:

[0007] obtaining branch electric parameters of each branch in the substation direct current system and electric bridge electric parameters collected based on an unbalanced electric bridge; wherein the unbalanced electric bridge is connected in series with each branch of the substation direct current system;

[0008] determining a branch in which a grounding fault exists in each branch according to the branch electric parameters and the electric bridge electric parameters;

[0009] obtaining node parameters of each node in the branch in which the grounding fault exists; the node of each branch comprises a parent node and at least one child node; the node parameters comprise 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 interval distance upper limit between the parent node and each child node;

[0010] determining a fault position point according to the node parameters of each node.

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

[0012] determining a fault state of the fault location point according to the fault location probability.

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

[0014] injecting a preset power supply signal into the unbalanced bridge, and obtaining an output electrical signal and a bridge resistance of the unbalanced bridge as the unbalanced bridge electrical parameters.

[0015] Optionally, the branch in which the ground fault exists is determined according to the branch electrical parameters and the unbalanced bridge electrical parameters, and includes:

[0016] ground resistances of the branches are respectively determined according to the branch electrical parameters and the unbalanced bridge electrical parameters.

[0017] the branch whose ground resistance is not within a preset resistance range is determined as the branch in which the ground fault exists.

[0018] Optionally, the fault location point is determined according to the node parameters of the nodes, and includes:

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

[0020]

[0021] wherein, φ up is an impedance of the parent node, φ dn is an impedance of the child node, d up is an upper limit of an interval distance between the parent node and the child node, L sec is a cable length between the parent node and the child node, and Δφ is a difference between the impedance between the parent node and the child node and the impedance φ up of the parent node;

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

[0023] Optionally, the fault location probability of the fault location point is obtained, and includes:

[0024] obtaining a fault occurrence probability and a fault early warning probability of the fault location point;

[0025] According to the fault occurrence probability and the fault early warning probability, a 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] Wherein, p(gj) is the fault occurrence probability, p(wi|gj) is the fault early warning probability, p(wi|kj) is the fault location probability, gj is suspected fault, and Fm is the fault location point set.

[0028] Optionally, the fault occurrence probability and the fault early warning probability of the fault location point are obtained, comprising:

[0029] The total number of faults of the substation DC system, the number of fault occurrences of the fault location point and the number of fault early warnings of the fault location point are obtained.

[0030] According to the number of fault occurrences and the total number of faults, the fault occurrence probability is determined.

[0031] According to the number of fault early warnings and the number of fault occurrences, the fault early warning probability is determined.

[0032] Optionally, according to the fault location probability, the fault state of the fault location point is determined, comprising:

[0033] It is judged whether the fault location probability is greater than or equal to a preset probability.

[0034] If yes, the fault location point is determined as a grounding fault point.

[0035] Optionally, the grounding fault positioning method of the substation DC system further comprises:

[0036] The wireless communication module is controlled to send the position information of the grounding fault point to a remote terminal.

[0037] The second aspect of the present application provides a grounding fault positioning device of a substation DC system, which comprises:

[0038] An electric parameter acquisition module is configured to acquire branch electric parameters of each branch of the substation DC system and electric bridge electric parameters collected based on an unbalanced electric bridge; wherein the unbalanced electric bridge is connected in series with each branch of the substation DC system.

[0039] A fault branch determination module is configured to determine a branch with a grounding fault in each branch according to the branch electric parameters and the electric bridge electric parameters.

[0040] a node parameter acquisition module, configured to acquire node parameters of each node in the branch in which the ground fault exists; each node of each 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 an upper limit of interval distance between the parent node and each child node;

[0041] a fault position determination module, configured to determine a fault position point according to the node parameters of each node;

[0042] a fault probability acquisition module, configured to acquire a fault position probability of the fault position point;

[0043] a fault state determination module, configured to determine a fault state of the fault position point according to the fault position probability.

[0044] The third aspect of the present application provides a grounding fault positioning system of a substation DC system, the grounding fault positioning system of the substation DC system comprising:

[0045] an impedance measurement module, a control module and a wireless communication module;

[0046] The impedance measurement module is configured to acquire an operating condition of the substation DC system.

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

[0048] In the embodiment of the present application, the branch electrical parameters of each branch in the substation DC system are acquired, and the bridge electrical parameters collected based on the unbalanced bridge in series with each branch of the substation DC system are acquired, so as to determine the branch in which the ground fault exists, thereby accurately determining the branch in which the ground fault exists and improving the efficiency of the grounding fault positioning system of the substation DC system. Meanwhile, the node parameters of each node in the branch in which the ground fault exists are acquired, so as to locate the fault position point in the branch in which the ground fault exists according to the node parameters of each node in the branch in which the ground fault exists, and the fault state of the fault position point is determined by acquiring the fault position probability of the fault position point, thereby evaluating the fault possibility of the fault position point and improving the accuracy of positioning the fault position point in the fault branch, thereby improving the reliability and safety of the substation DC system.

[0049] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments description. Obviously, the drawings described in the following are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0051] Figure 1 is a flowchart of a grounding fault positioning method of a substation DC system provided by the first embodiment of the present application;

[0052] Figure 2 is a circuit structure schematic diagram of a substation DC system provided by the first embodiment of the present application;

[0053] Figure 3 is a structure schematic diagram of an unbalanced bridge provided by the first embodiment of the present application;

[0054] Figure 4 is a flowchart of a grounding fault positioning method of a substation DC system provided by the second embodiment of the present application;

[0055] Figure 5 is a flowchart of a grounding fault positioning method of a substation DC system provided by the third embodiment of the present application;

[0056] Figure 6 is a flowchart of a grounding fault positioning method of a substation DC system provided by the fourth embodiment of the present application;

[0057] Figure 7 is a structure schematic diagram of a grounding fault positioning device of a substation DC system provided by the fifth embodiment of the present application;

[0058] Figure 8 is a structure schematic diagram of a grounding fault positioning system of a substation DC system provided by the sixth embodiment of the present application. DETAILED DESCRIPTION

[0059] In order to make the person skilled in the art better understand the present application, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0060] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and in the above drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0061] Embodiment one

[0062] Figure 1 is a flowchart of a grounding fault positioning method of a substation DC system provided by the first embodiment of the present application. The present embodiment can be applicable to the case of positioning the grounding fault position point in the substation DC system. The method can be executed by a grounding fault positioning device of the substation DC system. The device can be realized by software and / or hardware, and can generally be integrated in the control module of the grounding fault positioning system of the substation DC system. Correspondingly, as shown in Figure 1 , the grounding fault positioning method of the substation DC system can include:

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

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

[0065] Specifically, the branch current value of each branch and the output current of the unbalanced bridge are acquired by a current sensor or a current transformer, the branch voltage value of each branch and the output voltage of the unbalanced bridge are acquired by a voltage sensor or a voltage transformer, and the branch impedance value of each branch can be calculated from 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 directly called from the memory when needed.

[0066] In an optional embodiment, the bridge electrical parameter based on the unbalanced bridge collected includes: injecting a preset power signal to the unbalanced bridge, and obtaining the output electrical signal and bridge resistance of the unbalanced bridge as the bridge electrical parameter.

[0067] As shown in Figure 3 The bridge can be specifically understood as a circuit structure composed of four resistors, and is 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-connected resistors are connected in parallel. In the unbalanced bridge, the resistance values of the four resistors can not be equal, so that the output voltage of the bridge is not zero when the bridge is in an unbalanced state.

[0068] Specifically, continuing to refer to Figure 2 The unbalanced bridge 4 is connected in series with each branch of the substation DC system. The preset power 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 through the current sensor and the voltage sensor respectively. The output current and output voltage of the unbalanced bridge, and the bridge resistance value of the unbalanced bridge are determined as the bridge electrical parameter, so that the overall resistance value of the substation DC system can be determined through the bridge resistance, the output current and the output voltage.

[0069] S102, according to the branch electrical parameter and the bridge electrical parameter, determining the branch in which the ground fault exists in each branch.

[0070] Specifically, according to the output current and the output voltage of the unbalanced bridge, the overall resistance value of the DC system of the transformer substation can be determined, and according to the overall resistance value, whether there is a faulty branch in the DC system of the transformer substation can be determined. For example, the overall resistance value of the DC system of the transformer substation can be compared with a set resistance value range. When the overall resistance value of the DC system of the transformer substation is within the set resistance value range, it can be determined that there is no faulty branch in the DC system of the transformer substation. When the overall resistance value of the DC system of the transformer substation is not within the set resistance value range, it can be determined that there is a faulty branch in the DC system of the transformer substation. At this time, the ground voltage of each branch can be determined according to the branch resistance of each branch, the bridge resistance of the unbalanced bridge, and the branch voltage of each branch. Then, according to the ground voltage 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 range of the preset normal grounding resistance value, it can be further determined whether the branch has a grounding fault, that is, the branch with a grounding resistance value not within the range of the preset normal grounding resistance value can be determined as the branch with a grounding fault. Thus, the branch with a grounding fault can be accurately determined, the efficiency of the grounding fault positioning system of the DC system of the transformer substation is improved, and the accuracy of positioning the grounding fault position point in the DC system of the transformer substation is improved.

[0071] S103, acquiring node parameters of each node in the branch with a grounding fault.

[0072] Each branch includes 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] The node in the branch can be understood as the connection point of the device in the branch. The parent node in the node can be understood as the connection point of the key device in the branch. The child node in the node can be understood as the connection point of the other device in the branch for assisting the work of the key device. For example, as shown in FIG. 1, if the branch with a grounding fault is branch 1, branch 1 includes switch 001, key device 002, and switch 003. The connection point of key device 002 is the parent node of the branch, and the connection points of switch 001 and switch 003 are the child nodes of the branch. Figure 2 The node impedance at the node can be understood as including the resistance and reactance at the node. The interval impedance between the parent node and the child node can be understood as 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 understood as 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 understood as the maximum distance limit between the parent node and the child node.

[0074] S104, determining 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 fault child node can be determined, and thus 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 ground fault can be accurately determined, which helps to quickly and accurately repair the ground fault in the DC system of the substation and ensures the continuous and stable operation of the DC system of the substation.

[0076] S105, obtaining the fault location probability of the fault location point.

[0077] The fault location probability of the fault location point can be specifically understood as the probability of the fault location point occurring a fault. By determining the probability of the fault location point occurring a fault, the misjudgment of the fault location point caused by the fluctuation of the power grid in the substation is avoided, so that the fault possibility of the fault location point can be more comprehensively evaluated, and the accuracy of positioning the fault location point in the fault branch is improved.

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

[0079] Specifically, the probability of the fault location point occurring a fault is compared with a preset probability. When the probability of the fault location point occurring a fault is greater than or equal to the preset probability, it is determined that the fault location point has a fault. When the probability of the fault location point occurring a fault 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 repositioned. By determining the fault state of the fault location point according to the fault location probability, the accuracy of positioning the fault location point in the fault branch is improved, thereby improving the reliability and safety of the DC system of the substation.

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

[0081] The preset probability can be specifically understood as a probability value set in advance under certain conditions, which is used as a reference standard or threshold for judging whether the fault location point is a ground fault point. For example, the preset probability can be 90%.

[0082] Specifically, after the fault location probability of the fault location point is determined, the fault location probability of the fault location point is compared with a 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 the fault location point exists a fault, 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, the fault location point in the fault branch should be repositioned, thereby improving the accuracy of positioning the fault location point in the fault branch.

[0083] In the embodiment, the branch electric parameters of each branch in the substation DC system and the bridge electric parameters collected based on the unbalanced bridge connected in series with each branch of the substation DC system are acquired to determine the branch in which the ground fault exists, so that the branch in which the ground fault exists can be accurately determined, and the efficiency of the ground fault positioning system of the substation DC system is improved; meanwhile, the node parameters of each node in the branch in which the ground fault exists are acquired to locate the fault location point in the branch in which the ground fault exists according to the node parameters of each node in the branch in which the ground fault exists, so that the fault location point in the branch in which the ground fault exists can be accurately positioned, and the fault state of the fault location point is determined by acquiring the fault location probability of the fault location point, so that the fault possibility of the fault location point can be more comprehensively evaluated, the accuracy of positioning the fault location point in the fault branch is improved, and the reliability and safety of the substation DC system are improved.

[0084] Embodiment Two

[0085] Figure 4 is a flowchart of a substation DC system ground fault positioning method provided by the embodiment two of the present application, the embodiment two of the present application is based on the above-mentioned embodiment, and the method for determining the branch in which the ground fault exists is described in detail, and correspondingly, as shown in Figure 4 , the substation DC system ground fault positioning method can include:

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

[0087] S202, determining the ground resistance of each branch according to the branch electric parameters and the bridge electric parameters.

[0088] Specifically, the bridge electrical parameter can include an output current of the unbalanced bridge, an output voltage of the unbalanced bridge, and a bridge resistance of the unbalanced bridge. According to the output current and the output voltage of the unbalanced bridge, it can be determined whether there is a fault branch in each branch of the substation DC system. For example, the overall resistance of the substation DC system can be calculated according to the output current and the output voltage of the unbalanced bridge, and it is judged whether the overall resistance is within a set resistance range. When the overall resistance is not within the set resistance range, the ground voltage of each branch can be calculated. Specifically, according to the bridge resistance value of the unbalanced bridge, the positive and negative bus-to-ground insulation resistance, and the branch voltage of the branch, the ground voltage of the branch can be determined. According to the branch current of the branch, the ground resistance of each branch can be calculated correspondingly.

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

[0090]

[0091] wherein, R a is the positive and negative bus-to-ground insulation resistance, R2 and R J is the bridge resistance of the unbalanced bridge, V + is the ground voltage of the branch, V is the branch voltage of the branch, and V can also be understood as the first end voltage of the branch.

[0092] S203, determining the branch with the ground resistance not within the preset resistance range as the branch with the ground fault.

[0093] wherein, the preset resistance range can be understood as the range of the normal value of the ground resistance. In the case of normal operation of the substation DC system, the value of the ground resistance will fluctuate within the preset resistance range. When the value of the ground resistance exceeds the preset range, it indicates that the substation DC system has a ground fault at this time. The preset resistance range can be set by past experience and rules.

[0094] Specifically, by judging whether the ground resistance value of each branch is within the preset resistance range, the branch with the ground resistance value not within the preset normal ground resistance value range is determined as the branch with the ground fault, and the branch with the ground resistance value within the preset normal ground resistance value range is determined as the branch without the ground fault. In this way, the ground fault of each branch can be more effectively determined by the ground resistance of each branch, thereby improving the accuracy of positioning the fault position point in the fault branch and improving the efficiency of the ground fault positioning system of the substation DC system.

[0095] S204, obtaining the node parameters of each node in the branch with the ground fault.

[0096] S205, determining the fault position point according to the node parameters of each node.

[0097] S206, obtaining the fault position probability of the fault position point.

[0098] S207, determining the fault state of the fault position point according to the fault position probability.

[0099] In the embodiment, the grounding resistances of each branch are determined according to the branch electrical parameters and the bridge electrical parameters, and the branch with the grounding resistance not in the preset resistance range is determined as the branch with the grounding fault. Through the preset resistance range, whether each branch has the grounding fault can be more effectively determined through the grounding resistances of each branch, so that the branch with the grounding fault in the substation DC system can be accurately determined, the accuracy of locating the fault position point in the fault branch is improved, and the efficiency of the grounding fault positioning system of the substation DC system is improved.

[0100] Embodiment three

[0101] Figure 5 is a flowchart of a grounding fault positioning method of a substation DC system provided by the embodiment three. Based on the above-mentioned embodiments, the method of determining the fault position point according to the node parameters of each node and obtaining the fault position probability of the fault position point is described in detail. Correspondingly, as shown in Figure 5 , the grounding fault positioning method of the substation DC system can include:

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

[0103] S302, determining the branch with the grounding fault in each branch according to the branch electrical parameters and the bridge electrical parameters.

[0104] S303, obtaining the node parameters of each node in the branch with the grounding fault.

[0105] S304, determining the fault distance based on the second calculation formula according to the node parameters of each node.

[0106] The second calculation formula is:

[0107]

[0108] Wherein, 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, and L secis the length of the cable between the parent node and the child node, and Δφ is the difference between the impedance between the parent node and the child node and the impedance φ of the parent node. up

[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 investigated respectively, and by substituting the impedance parameter and the distance parameter of each node into the second calculation formula, the relative distance between each child node and the parent node can be calculated. 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, determining the fault position point according to the fault distance.

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

[0112] S306, obtaining the fault occurrence probability and the fault warning probability of the fault position point.

[0113] The fault occurrence probability of the fault position point can be specifically understood as the proportion of the fault occurrence times of the fault position point to the total fault times of the substation DC system, and the fault warning probability can be specifically understood as the proportion of the fault warning times of the fault position point to the fault occurrence times of the fault position point.

[0114] In an optional embodiment, obtaining the fault occurrence probability and the fault warning probability of the fault position point includes: obtaining the total fault times of the substation DC system, the fault occurrence times of the fault position point, and the fault warning times of the fault position point; determining the fault occurrence probability according to the fault occurrence times and the total fault times; and determining the fault warning probability according to the fault warning times and the fault occurrence times.

[0115] The fault occurrence probability p(g j ) can be calculated based on the following formula:

[0116]

[0117] Wherein, n(g j ) is the fault occurrence times of the fault position point, and n(g) is the total fault times of the substation DC system.

[0118] The fault warning probability p(w i | g j ​) can be calculated based on the following formula:

[0119]

[0120] wherein n(g k ) is the number of fault warning of the fault location point, and n(g j ) is the number of fault occurrence of the fault location point.

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

[0122] wherein the improved Bayesian network model is:

[0123]

[0124] wherein p(gj) is the fault occurrence probability, p(wi|gj) is the fault warning probability, p(wi|kj) is the fault location probability, gj is the suspected fault, and Fm is the fault location point set.

[0125] wherein the Bayesian network model can be understood as a kind of probabilistic graphical model, which is used to describe the probability dependence relationship between different variables. Specifically, according to the calculated fault occurrence probability and fault warning probability, the relationship between the fault warning and the actual occurrence probability of the fault location point can be determined based on the improved Bayesian network model, so as to calculate 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 the fault location point exists fault. 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 repositioned, so as to realize the accurate positioning of the fault location point in the branch with ground fault.

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

[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 as to accurately position the fault location point in the branch with ground fault. 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 exists fault, so as to more comprehensively evaluate the fault possibility of the fault location point, and realize the accurate positioning of the fault location point in the branch with ground fault.

[0128] Embodiment Four

[0129] Figure 6 is a flowchart of a grounding fault positioning method of a substation DC system provided by Embodiment Four of the present application. Based on the above-mentioned embodiments, the present embodiment makes a detailed description of the method for determining the fault state of the fault position point according to the fault position probability and the post-processing method after the fault position point is determined. Correspondingly, as shown in Figure 6 , the grounding fault positioning method of the substation DC system can include the following steps.

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

[0131] S402, determining a branch in which a grounding fault exists in each branch according to the branch electrical parameters and the bridge electrical parameters.

[0132] S403, acquiring node parameters of each node in the branch in which the grounding fault exists.

[0133] S404, determining a fault position point according to the node parameters of each node.

[0134] S405, acquiring a fault position probability of the fault position point.

[0135] S406, determining a fault state of the fault position point according to the fault position probability.

[0136] S407, controlling a wireless communication module to send position information of the grounding fault point to a remote terminal.

[0137] Specifically, after the grounding fault point is determined, the wireless communication module can be controlled to send the position information of the grounding fault point to the remote terminal, so as to inform the operation and maintenance personnel that the substation DC system has a grounding fault and the position information of the grounding fault point, and the grounding fault position point needs to be overhauled, thereby quickly and accurately repairing the grounding fault existing in the substation DC system and ensuring the continuous and stable operation of the substation DC system. The method for sending the position information of the grounding fault point can include but is not limited to an email, a short message, or other remote notifications, as long as the operation and maintenance personnel can be informed that the substation DC system has a grounding fault and the position information of the grounding fault point, and the grounding fault position point needs to be overhauled. The present application does not make a specific limitation on this.

[0138] In this embodiment, the wireless communication module is controlled to send the position information of the grounding fault point to the remote terminal, so as to inform the operation and maintenance personnel that the grounding fault exists in the DC system of the substation and the position information of the grounding fault point, and the grounding fault position point needs to be repaired, thereby quickly and accurately repairing the grounding fault existing in the DC system of the substation, and ensuring the continuous and stable operation of the DC system of the substation.

[0139] Embodiment five

[0140] Figure 7 is a structural schematic diagram of a grounding fault positioning device of a substation DC system provided by the embodiment five of the present application. The device can realize the grounding fault positioning method of the substation DC system provided by the embodiment of the present application, and can be realized by software and / or hardware, and can be generally integrated in the control module of the grounding fault positioning system of the substation DC system. As shown in the figure, the device comprises: Figure 7

[0141] The electric parameter acquisition module 501 is configured to acquire the branch electric parameters of each branch of the substation DC system and the bridge electric parameters acquired based on the unbalanced bridge.

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

[0143] The fault branch determination module 502 is configured to determine the branch in which the grounding fault exists in each branch according to the branch electric parameters and the bridge electric parameters.

[0144] The node parameter acquisition module 503 is configured to acquire the node parameters of each node in the branch in which the grounding fault exists.

[0145] Each node of each branch comprises a parent node and at least one child node, and the node parameters comprise 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 position determination module 504 is configured to determine the fault position point according to the node parameters of each node.

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

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

[0149] In an optional embodiment of the present application, the electric parameter acquisition module 501 can also be configured to inject a preset power signal into the unbalanced bridge, and acquire the output electric signal of the unbalanced bridge and the bridge resistance as the bridge electric parameters. ​

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

[0151] In one embodiment of the present application, the fault position determination module 504 can be further configured to determine the fault distance d based on a second calculation formula according to the node parameters of each node, and determine the fault position point according to the fault distance.

[0152] wherein the second calculation formula is:

[0153]

[0154] wherein, 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, is the difference between the impedance between the parent node and the child node and the impedance of the parent node.

[0155] In one embodiment of the present application, the fault probability acquisition module 505 can be further configured to acquire the fault occurrence probability and the fault warning probability of the fault position point, and determine the fault position probability of the fault position point based on the improved Bayesian network model according to the fault occurrence probability and the fault warning probability.

[0156] wherein the improved Bayesian network model is:

[0157]

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

[0159] In one embodiment of the present application, the fault probability acquisition module 505 can be further configured to acquire the total number of faults of the substation DC system, the number of fault occurrences of the fault position point, and the number of fault warnings of the fault position point, determine the fault occurrence probability according to the number of fault occurrences and the total number of faults, and determine the fault warning probability according to the number of fault warnings and the number of fault occurrences.

[0160] In one embodiment of the present application, the fault state determination module 506 can be further configured to determine whether the fault position probability is greater than or equal to a preset probability, and determine the fault position point as the grounding fault point if yes. ​

[0161] In one embodiment of the present application, the fault state determining module 506 can also be configured to control the wireless communication module to send the location information of the ground fault point to a remote terminal.

[0162] The substation DC system ground fault locating device described above can execute the substation DC system ground fault locating method provided by any embodiment of the present application, has the function modules and beneficial effects corresponding to the execution method. The technical details not described in detail in the present embodiment can be referred to the substation DC system ground fault locating method provided by any embodiment of the present application.

[0163] Since the substation DC system ground fault locating device described above is a device that can execute the substation DC system ground fault locating method in the embodiments of the present application, based on the substation DC system ground fault locating method described in the embodiments of the present application, those skilled in the art can understand the specific implementation of the substation DC system ground fault locating device of the present embodiment and its various forms, so here the substation DC system ground fault locating device how to realize the substation DC system ground fault locating method in the embodiments of the present application will not be described in detail. As long as the device used to implement the substation DC system ground fault locating method in the embodiments of the present application is implemented by those skilled in the art, it belongs to the scope of the present application.

[0164] Embodiment six

[0165] Figure 8 is a structural schematic diagram of a substation DC system ground fault locating system provided by the sixth embodiment of the present application. The substation DC system ground fault locating system can implement the substation DC system ground fault locating method provided by the embodiments of the present application, as shown in Figure 8 The substation DC system ground fault locating 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 condition of the substation DC system.

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

[0168] The substation DC system ground fault locating system described above can execute the substation DC system ground fault locating method provided by any embodiment of the present application, has the function modules and beneficial effects corresponding to the execution method. The technical details not described in detail in the present embodiment can be referred to the substation DC system ground fault locating method provided by any embodiment of the present application.

[0169] Since the substation DC system grounding fault locating system described above is a system that can perform the substation DC system grounding fault locating method in the embodiments of the present application, based on the substation DC system grounding fault locating method described in the embodiments of the present application, those skilled in the art can understand the specific implementation of the substation DC system grounding fault locating system of the embodiments and its various forms of changes, so here the substation DC system grounding fault locating system how to implement the substation DC system grounding fault locating method in the embodiments of the present application will not be described in detail. As long as the system used to implement the substation DC system grounding fault locating method in the embodiments of the present application is implemented by those skilled in the art, it belongs to the scope of protection of the present application.

[0170] It should be understood that various forms of flow shown above can be used to reorder, add or delete steps. For example, each step described in the present application can be executed in parallel, sequentially or in different order, as long as the desired results of the technical solutions disclosed in the present application can be achieved, which is not limited herein.

[0171] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for locating grounding faults in a substation DC system, characterized in that, include: Obtain the branch electrical parameters of each branch in the DC system of the substation, as well as the bridge electrical parameters collected based on the unbalanced bridge; wherein the unbalanced bridge is connected in series with each branch of the DC system of the substation. Based on the electrical parameters of each branch and the electrical parameters of the bridge, determine the branch with a ground fault in each branch; Obtain the node parameters of each node in the branch with the grounding fault; each node in the branch includes 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; the nodes of the branch are the equipment connection points in the branch, the parent node is the connection point of the critical equipment in the branch, and the child node is the connection point of other equipment in the branch used to assist the operation of the critical equipment; Determining the fault location point based on the node parameters of each node includes: determining the fault distance d based on the node parameters of each node and a second calculation formula; the second calculation formula is: ； Where, φ up φ is the impedance of the parent node. dn Let d be the impedance of the child node. up L is the upper limit of the interval distance between the parent node and the child node. sec The length of the cable between the parent node and the child node is given by Δφ, where Δφ is the impedance between the parent node and the child node and the impedance φ of the parent node. up The difference between them; the fault location point is determined based on the fault distance; Obtain the fault location probability of the fault location point; The fault state of the fault location point is determined based on the fault location probability.

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

3. The method for locating ground faults in a substation DC system according to claim 1, characterized in that, Based on the electrical parameters of each branch and the electrical parameters of the bridge circuit, the branches with ground faults are identified, including: Based on the electrical parameters of each branch and the electrical parameters of the bridge, determine the grounding resistance of each branch respectively; The branch whose grounding resistance is not within the preset resistance range is identified as the branch with a grounding fault.

4. The method for locating ground faults in a substation DC system according to claim 1, characterized in that, Obtaining the fault location probability of the fault location point includes: Obtain the probability of fault occurrence and the probability of fault warning at the fault location point; Based on the fault occurrence probability and the fault warning probability, the fault location probability of the fault location point is determined using an improved Bayesian network model; the improved Bayesian network model is as follows: ； Among them, p(g j p(w) represents the probability of the fault occurring. i |g j p(w) represents the fault warning probability. i |k j ) represents the probability of the fault location, g j F is suspected of being a fault. m This is the set of fault location points.

5. The grounding fault location method for a substation DC system according to claim 4, characterized in that, Obtaining the probability of fault occurrence and the probability of fault warning at the fault location point includes: Obtain the total number of faults in the DC system of the substation, the number of fault occurrences at the fault location point, and the number of fault warnings at the fault location point; The probability of a failure is determined based on the number of failures and the total number of failures. The probability of a fault warning is determined based on the number of fault warnings and the number of fault occurrences.

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

7. The method for locating ground faults in a substation DC system according to claim 6, characterized in that, Also includes: The wireless communication module is controlled to send the location information of the grounding fault point to the remote terminal.

8. A ground fault location device for a substation DC system, characterized in that, include: An electrical parameter acquisition module is used to acquire the branch electrical parameters of each branch in the DC system of the substation, as well as the bridge electrical parameters acquired based on the unbalanced bridge; wherein the unbalanced bridge is connected in series with each branch of the DC system of the substation. The fault branch determination module is used to determine the branch with a grounding fault in each of the branches based on the electrical parameters of each branch and the electrical parameters of the bridge. A node parameter acquisition module is used to acquire the node parameters of each node in the branch with a grounding fault; each node in the branch includes 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 two nodes; the nodes of the branch are the equipment connection points in the branch, the parent node is the connection point of the critical equipment in the branch, and the child node is the connection point of other equipment in the branch used to assist the operation of the critical equipment; The fault location determination module is used to determine the fault location point based on the node parameters of each node; determining the fault location point based on the node parameters of each node includes: determining the fault distance d based on the node parameters of each node and a second calculation formula; the second calculation formula is: ； Where, φ up φ is the impedance of the parent node. dn Let d be the impedance of the child node. up L is the upper limit of the interval distance between the parent node and the child node. sec The length of the cable between the parent node and the child node is given by Δφ, where Δφ is the impedance between the parent node and the child node and the impedance φ of the parent node. up The difference between them; the fault location point is determined based on the fault distance; The fault probability acquisition module is used to acquire the fault location probability of the fault location point. The fault status determination module is used to determine the fault status of the fault location point based on the fault location probability.

9. 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 substation's DC system. 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 according to any one of claims 1-7.

Images