A modeling method for short-circuit fault propagation model under multiple relay protection devices failure to operate

Abstract

The present invention relates to the technical field of power systems, and specifically to a modeling method for a short-circuit fault propagation model under the failure of multiple relay protection devices to operate, comprising the following steps: S1, constructing a substation model and protection and circuit breaker configuration: describing the configuration mode of the protection device and circuit breaker of the substation and their mutual relationship; S2, defining the short-circuit fault propagation mechanism under the failure of protection: analyzing the propagation process and the impact range of the short-circuit fault under the failure of protection device in the substation; S3, constructing an abstract graph model: converting the topological structure of the substation into an abstract graph to describe the positional relationship of each component and the fault propagation path; S4, short-circuit fault propagation modeling: using a multi-commodity flow model and the action logic of the protection device to simulate the propagation and removal process of the short-circuit fault under the failure of the protection device. The present invention helps to better understand and design the protection configuration in the substation, and improves the safety and reliability of the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices to operate. Background Art

[0002] The safety and stability of the power system is of vital importance. With the development of attack methods, attacks on protection devices have become a huge threat to the power grid. Once the protection equipment is attacked, it is easy to cause failure of the protection equipment and refusal of related circuit breakers, which will cause short-circuit faults to spread over a large area within the power grid, resulting in a large amount of load loss in the system and even triggering cascading failures. In this context, how to accurately model the propagation of short-circuit faults based on the actual topology of substations has become the focus of research on related issues.

[0003] The fault propagation process of the power system is closely related to the busbar structure, topology, protection configuration and action logic of the substation. However, in most studies on short-circuit fault propagation models under the refusal of relay protection devices, the above factors are rarely considered at the same time. The internal topology of the substation is not fully considered in the modeling. The substation with two buses is simply represented by two nodes connected by circuit breakers. This representation method is only applicable to specific busbar wiring methods (such as single busbar wiring and double busbar segmented wiring), and cannot describe substations with complex fault propagation and component connection relationships. Although the internal topology and busbar structure of the substation are considered, the protection types are not classified. The coupling logic is set as: one set of protection devices controls one circuit breaker. The modeling is relatively rough, and the protection action logic in some substations does not match the actual situation. In actual scenarios, each set of protection has its own protection range, and its action is usually associated with multiple circuit breakers, such as transformer protection, busbar protection, etc. If the above factors cannot be fully considered, it is difficult to achieve accurate modeling during the simulation process.

[0004] The present invention is based on the actual wiring diagram inside the substation. By analyzing the logical relationship between various types of protection and circuit breaker actions, the substation topology structure changes when the protection device refuses to operate are obtained, and an abstract graph model is introduced to convert the power system topology diagram into an abstract graph. The short-circuit fault propagation model is modeled based on the abstract graph. This model can accurately reflect the fault propagation and removal process when a short-circuit fault occurs in any transmission line in the system, and can accurately obtain the status of each node, line, and circuit breaker and derive the impact range of the short-circuit fault. Summary of the invention

[0005] Based on the above purpose, the present invention provides a method for modeling a short-circuit fault propagation model under the refusal of multiple relay protection devices.

[0006] A method for modeling a short-circuit fault propagation model under multiple relay protection device refusal to operate comprises the following steps:

[0007] S1, construct substation model and configuration of protection devices and circuit breakers: describe the configuration of protection devices and circuit breakers in substation and their relationship;

[0008] S2, define the short-circuit fault propagation mechanism under protection failure: analyze the propagation process and impact range of short-circuit faults under protection failure in substations;

[0009] S3, construct an abstract graph model: convert the substation topology into an abstract graph to describe the position relationship of each component and the fault propagation path;

[0010] S4, short-circuit fault propagation modeling: using the multi-commodity flow model and the action logic of the protection device, simulate the propagation and removal process of the short-circuit fault when the protection device refuses to operate.

[0011] Furthermore, the construction of the substation model and the configuration of the protection device and circuit breaker in S1 includes:

[0012] S11, Hub substation classification: Hub substation is located at the hub point of the power system. The voltages of the high voltage side, medium voltage side and low voltage side of the hub substation are 500 (750) kV, 220 (330) kV and 35 kV respectively;

[0013] S12, relay protection device configuration: The substation is equipped with relay protection devices for transmission lines and main equipment. The relay protection devices include transmission line protection, busbar protection and transformer protection. The relay protection configuration is configured according to the voltage level and wiring method of the substation.

[0014] Furthermore, the relay protection device configuration in S12 includes:

[0015] S121, high voltage side wiring: The high voltage side of the hub substation adopts a one and a half circuit breaker wiring method;

[0016] S122, transformer protection: The main protection of the transformer is longitudinal differential protection and heavy gas protection, and the backup protection adopts zero-sequence current protection, overcurrent protection and impedance protection;

[0017] S123, transmission line protection: The main protection of the transmission line is the full-line fast-acting longitudinal protection, and the backup protection is distance protection and zero-sequence current protection;

[0018] S124, busbar protection: busbar protection is busbar differential protection.

[0019] Furthermore, the short-circuit fault propagation mechanism under protection refusal defined in S2 includes:

[0020] S21, protection device fails to operate: If the line protection device fails to operate, the short circuit fault will propagate to the hub substation through the closed circuit breaker;

[0021] S22, fault propagation process: During the fault propagation process, it will affect the adjacent protection devices, causing the relay protection devices of the adjacent lines and equipment to trip the circuit breakers, thus expanding the scope of the power outage;

[0022] S23, automatic reclosing: The automatic reclosing is performed on the principle of first reclosing the side circuit breaker and then the middle circuit breaker.

[0023] Furthermore, the construction of the abstract graph model in S3 includes:

[0024] S31, abstract graph conversion: convert the hub substation topology graph into an abstract graph, where the vertices of the abstract graph are the lines and nodes of the topology graph, and the edges of the abstract graph are the circuit breakers of the topology graph;

[0025] S32, region division: the vertices of the topological graph are regarded as the same region, the same region represents the same operating (fault) state, and the circuit breaker divides the entire power system into multiple independent regions;

[0026] S33, define protection scope and control logic: describe the configuration and fault isolation logic of the relay protection device in the abstract diagram.

[0027] Furthermore, the definition of protection scope and control logic in S33 includes:

[0028] S331, Vertex protection: In the abstract graph, each type of protection vertex is equipped with a corresponding relay protection device, and the protection range of the relay protection device is the range of the vertex and all its adjacent edges;

[0029] S332, control logic: each edge is controlled by the relay protection devices of two adjacent vertices at the same time;

[0030] S333, fault isolation: when a short circuit fault occurs at a vertex, the corresponding relay protection device controls all circuit breakers around the vertex to operate to isolate the fault;

[0031] S334, control in the event of failure: If the relay protection device of a vertex fails, the corresponding relay protection device cannot control the operation of the relevant circuit breakers. When the relay protection device of an adjacent vertex identifies a fault, the relay protection device of the adjacent vertex controls all circuit breakers around the vertex where the relay protection device fails to trip.

[0032] Furthermore, the short circuit fault propagation modeling in S4 includes:

[0033] S41, short-circuit fault propagation process in phase A: Analyze the propagation path of the short-circuit fault when the relay protection device fails to operate, and describe the propagation state of the fault from the source vertex to each destination vertex and its impact through an abstract graph model;

[0034] S42, Phase B short-circuit fault removal process: describes the action process of the relay protection device after identifying the short-circuit fault and analyzes the circuit breaker tripping logic.

[0035] Furthermore, the short-circuit fault propagation process in stage A in S41 includes:

[0036] S411, multi-commodity flow model: A multi-commodity flow model is used to represent the short-circuit fault propagation process in the abstract graph. The impact of the short-circuit fault is regarded as a commodity, the vertex that suffers effective physical attack is regarded as the commodity source, the edge is regarded as the path of the network flow, and all vertices are regarded as destinations. The commodity consumption of each destination is 0 or 1, representing the fault state of the vertex. The calculation formula is:

[0037]

[0038] in, is the edge state of stage A, E is the edge set of the abstract graph, is a continuous variable, is a binary variable representing whether node i has a short circuit fault, and V is the set of vertices in the abstract graph;

[0039] S412, circuit breaker action logic: Since the circuit breaker is controlled by two protection devices at the same time, when one or both of the two adjacent vertices in the abstract graph have a short circuit fault, the circuit breaker connecting the two vertices will trip. The calculation formula is:

[0040]

[0041]

[0042] S413, Sideline state constraint: Sideline state in phase A The constraints are expressed as:

[0043]

[0044] Among them, V T 、V L 、V B They are respectively the sets of transformer vertices, transmission line vertices, and busbar vertices of the abstract graph.

[0045] Furthermore, the short-circuit fault removal process in stage B in S42 includes:

[0046] S421, protection device action state: When the short-circuit fault in phase A propagates to the protection area of ​​the node, the relevant circuit breaker trips and isolates the fault. The calculation formula for the constraint of the protection device action state in phase B is:

[0047]

[0048] S422, circuit breaker tripping logic: determine the protection action status and the circuit breaker trip logic for phase B The constraint relationship is calculated as follows:

[0049]

[0050] S423, Final sideline status: Determine the final sideline status The constraint is calculated as follows:

[0051]

[0052] Beneficial effects of the present invention:

[0053] The present invention, by analyzing a typical substation model and the protection and circuit breaker configuration, clarifies the logical relationship between the protection control-related circuit breaker actions, and sorts out the propagation mechanism of short-circuit faults within and between substations under protection refusal. The detailed analysis helps to better understand and design the protection configuration within the substation, thereby improving the safety and reliability of the power system.

[0054] The present invention clearly describes the status of circuit breakers and related equipment in the power topology diagram through the edges of the abstract diagram, provides a basis for subsequent modeling and programming, simplifies the analysis process of complex power systems, and makes the logic of fault propagation and isolation more intuitive and easy to understand.

[0055] The present invention, by refining the short-circuit fault propagation process into two stages, A and B, and modeling based on abstract graphs and protection propagation logic, constructs a detailed model that can clearly reflect the short-circuit fault propagation process and the state of each component in the system after the fault is removed. This model not only improves the accuracy of fault analysis, but also provides a theoretical basis for formulating effective fault isolation strategies, which helps to improve the overall stability and recovery capability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 This is a schematic diagram of the main connection of the high voltage side of a typical substation according to an embodiment of the present invention;

[0058] Figure 2 A schematic diagram of a power system topology according to an embodiment of the present invention;

[0059] Figure 3 is an abstract schematic diagram of an embodiment of the present invention;

[0060] Figure 4 The figure is a flow chart of a modeling method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0061] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0062] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0063] like Figure 1-Figure 4 As shown, a method for modeling a short-circuit fault propagation model under multiple relay protection devices failing to operate includes the following steps:

[0064] 1. Typical substation model and protection and circuit breaker configuration:

[0065] Substations are places in the power system that transform voltage and current, receive and distribute electric energy. They are generally divided into hub substations, regional important substations and general substations. Among them, hub substations are located at the hub of the power system. The voltage on the high-voltage side is generally 500 (750) kV, and the voltage on the medium and low voltage sides is generally 220 (330) kV and 35 kV. Substations are equipped with relay protection devices for transmission lines and main equipment, such as: transmission line protection, busbar protection, transformer protection, etc. According to the voltage level and wiring method of the substation, there are certain differences in the protection configuration. For example, the high and low voltage side busbar protection of 500kV substations are both configured in dual configuration; the high-voltage side busbar protection of 220kV substations is configured in double sets, and the low-voltage side (110KV) busbar protection is configured in a single set; 110kV substations generally do not have dedicated busbar protection.

[0066] In a 500kV substation, the high-voltage side generally adopts a one-and-a-half circuit breaker wiring method. The transformers, transmission lines, busbars and other equipment on the high-voltage side are generally equipped with dual protection measures. The two sets of protection AC voltage, AC current, DC power supply, communication equipment, tripping coils, etc. are independent of each other. Among them, the main protection of the transformer is longitudinal differential protection and heavy gas protection, and the backup protection generally adopts zero-sequence current protection, overcurrent protection, impedance protection, etc.; the main line protection is full-line fast-acting longitudinal protection, and the backup protection is distance protection, zero-sequence current protection, etc.; the busbar protection is generally busbar differential protection.

[0067] Figure 1 This is a schematic diagram of the main connection of the high-voltage side of a typical substation. During normal operation, all circuit breakers are in a closed state. When there is a short-circuit fault in the system, the protection device installed on the equipment affected by the short-circuit fault can control all circuit breakers directly connected to the equipment to trip, isolate the fault area from the normal area, and avoid fault propagation. The corresponding relationship between various types of protection devices and circuit breakers is shown in Table 1. It can be seen from Table 1 that the protection device of each type of equipment can control all circuit breakers directly connected to the equipment. When a short-circuit fault occurs in the L1 line, the line protection will quickly disconnect the circuit breakers 1DL and 2DL; when the protection device of the #1 transformer identifies a short-circuit fault, the protection controllable switches 7DL, 8DL, 10DL, and 11DL will trip; when the 500kVⅠ busbar protection identifies a short-circuit fault, the protection controllable switches 1DL, 4DL, and 7DL will trip.

[0068] Table 1 Correspondence between protection devices and circuit breakers

[0069]

[0070] 2. Short-circuit fault propagation mechanism under protection refusal:

[0071] A typical substation uses a half-circuit breaker wiring method on the high voltage side. Figure 1As shown, all circuit breakers are in the closed state during normal operation. When the line protection device of L1 refuses to operate, if there is a short circuit fault in the L1 line. At this time, the system fault transfer and circuit breaker operation status are as follows:

[0072] (1) After L1 is short-circuited, the circuit breakers 1DL and 2DL that should have operated remain closed and do not operate. The short-circuit fault propagates into the substation through the closed circuit breakers and affects adjacent protection devices.

[0073] (2) Affected by the propagation of the fault, the line protection of L2 and L3 lines and the transformer protection of #1 transformer are activated, and the circuit breakers 2DL, 3DL, 4DL, 5DL, 7DL and 8DL in the station are tripped. At this time, the 500kV bus I, lines L2, L3 and #1 transformer are out of operation.

[0074] (3) After the protection device is activated, the automatic reclosing integrated in the circuit breaker protection starts to operate. The reclosing principle is: reclose the side circuit breaker first, then reclose the middle circuit breaker. If the side circuit breaker fails to reclose, the middle circuit breaker will no longer reclose. After the reclosing is completed, only the circuit breaker 3DL is successfully closed. At this time, the line L3 resumes power supply via the 500kV bus II.

[0075] Under the above action logic, when a single type of protection fails: it may cause other equipment in the station to be affected and power outage, expanding the scope of the power outage. Due to the timely action of other types of protection, the fault is isolated inside the substation and cannot continue to spread to other substations along the transmission line. If multiple protections fail to operate at the same time, the fault will further spread into the system along the closed circuit breaker.

[0076] If the line protection of L1 and L2 and the protection of transformer #2 fail to operate at the same time. When a short circuit fault occurs in line L1, the circuit breakers 1DL and 2DL controlled by the line protection of L1 do not operate, and the short circuit fault propagates along circuit breaker 1DL to line L2 and transformer #1, and propagates along circuit breaker 2DL to line L3. At this time, 2DL, 3DL, 7DL, and 8DL are controlled to trip, and 4DL and 5DL do not operate due to the failure of line protection of L1. The short circuit fault continues to propagate along 4DL and 5DL to transformer #2. Due to the failure of transformer #2 protection, circuit breakers 5DL and 6DL do not operate, and the short circuit fault continues to affect line L4 and causes 9DL to trip.

[0077] 3. Abstract graph model:

[0078] In order to accurately describe the positional relationship of each component of the power system connection, the power system topology diagram is converted into an abstract diagram. First, the lines, nodes, circuit breakers and other elements in the topology diagram are matched with the edges and vertices in the abstract diagram. The corresponding relationship is as follows:

[0079] (1) The lines and nodes of the topological graph correspond to the vertices of the abstract graph.

[0080] (2) The circuit breakers in the topological graph correspond to the edges in the abstract graph.

[0081] The vertices of the topology graph can be regarded as the same area, and the same area represents the same operating (fault) state. The circuit breaker divides the entire power system into multiple independent areas. In the system that protects normal operation, the circuit breaker can isolate the faults in each area to avoid propagation.

[0082] The abstract graph can be obtained by the above method. It can be seen that Figure 2 It is a topological diagram of the power system, where the lines are represented by L and the nodes are represented by B; Figure 3 is the corresponding abstract graph, with vertices represented by V. According to the different node categories and functions of the topology graph, the vertices in the abstract graph can be divided into: busbar protection vertex, transmission line protection vertex, and transformer protection vertex. For example: B1 corresponds to busbar vertex V1, L3-12 corresponds to transmission line vertex V3, B5 and B2 correspond to transformer vertices V5 and V2; circuit breakers 9-14, 18-19, and 23-24 correspond to V9-V13, V24-V19, and V16-V7, respectively.

[0083] In the abstract graph, each type of protection vertex can be considered to be equipped with such a protection device. The protection range of the protection device is the range of the vertex and all adjacent edges. Each edge is controlled by the protection devices of two adjacent vertices at the same time. When a short circuit fault occurs at a vertex, the protection device can control the operation of all circuit breakers around the vertex to isolate the fault. If the protection device of the vertex fails, the protection device cannot control the operation of the related circuit breakers. When the protection device of the adjacent vertex identifies the fault, the protection device controls all circuit breakers around the vertex to trip.

[0084] 4. Short circuit fault propagation modeling:

[0085] According to the abstract graph rules and protection action logic, the short-circuit fault propagation process can be subdivided into the process of fault propagation caused by the refusal of the protection device to operate and the process of fault isolation caused by the successful operation of the protection device. The above processes are named stage A and stage B respectively.

[0086] Phase A. Short circuit fault propagation process:

[0087]

[0088] Formulas (1)-(3) use a multi-commodity flow model to represent the short-circuit fault propagation process in the abstract graph: the impact of the short-circuit fault is taken as the commodity, the vertex that suffers effective physical attack is taken as the commodity source, the edge is taken as the path of the network flow, all vertices are taken as the destination, and the commodity consumption of each destination is 0 or 1, representing the fault state of the vertex. Among them, formula (1) means that the vertices connected by the edge with state 1 in the abstract graph are in the same state, is the edge state of stage A, and E is the edge set of the abstract graph. Formula (2) indicates that there is no commodity flow on the edge corresponding to the circuit breaker in the disconnected state. is a continuous variable, representing the commodity flow flowing on the edge. Formula (3) indicates that the vertex with state 1 is the source of the commodity flow. It produces at least one commodity, which can be consumed at the vertex or flow out along the edge. The vertex with state 0 does not produce any commodity. If there is a commodity flow source in a set of connected vertices, the fault states of these vertices are all 1, otherwise the fault states are all 0. is a binary variable representing whether a vertex has a short circuit fault. Indicates that there is a short circuit fault at node i, and V is the set of vertices in the abstract graph.

[0089]

[0090] Formulas (4)-(6) represent the action logic of the circuit breaker controlled by the protection device under short-circuit fault: Since the circuit breaker is controlled by two protection devices at the same time, when there is a short-circuit fault at any or both of the two adjacent vertices in the abstract graph, the circuit breaker connecting the two vertices will trip. Its action logic is

[0091]

[0092]

[0093] Formulas (7)-(10) are the sideline states in stage A The constraints jointly represent the relationship between the operating state of the protection device, the circuit breaker action logic and the edge state of the abstract graph under short-circuit fault: in two adjacent protection areas, when the protection devices of the two areas operate normally, the circuit breaker connecting the two areas trips, and the edge state of the circuit breaker is When the protection device of one area fails, all circuit breakers under the control of the failed protection device will not operate. If the adjacent normal operating protection is the transmission line protection or transformer protection, the circuit breaker connecting the two areas will be tripped under the control of the protection. The state of the side line where the circuit breaker is located If the adjacent normal operation protection is busbar protection, the line short circuit fault will not trigger the busbar protection, so the circuit breaker connecting the two areas will not operate, and the edge state of the circuit breaker is When the protection devices of two adjacent areas fail, the circuit breaker connecting the two areas does not operate, and the state of the edge line where the circuit breaker is located V T 、V L 、V B They are respectively the sets of transformer vertices, transmission line vertices, and busbar vertices of the abstract graph.

[0094] Phase B. Short circuit fault removal process:

[0095]

[0096] Formulas (11)-(13) are the operating states of the protection device in stage B. When the short-circuit fault in phase A propagates to the protection area of ​​node i, It indicates that the node protection device is activated, the related circuit breaker trips and isolates the fault.

[0097]

[0098] Formulas (14)-(16) represent the protection action status and the circuit breaker trip logic for phase B The constraint relationship of . Equations (17)-(18) represent the final edge state of the system constraints.

[0099] Through the above model, the system line short circuit fault state can be accurately obtained Protection device refusal to operate state α i , protection action removal status Circuit breaker two-stage tripping logic and And the final sideline status relationship.

[0100] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0101] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for modeling a short-circuit fault propagation model under multiple relay protection device refusal to operate, characterized in that: The following steps are involved: S1, construct substation model and configuration of protection devices and circuit breakers: describe the configuration of protection devices and circuit breakers in substation and their relationship; S2, define the short-circuit fault propagation mechanism under protection failure: analyze the propagation process and impact range of short-circuit faults under protection failure in substations; S3, construct an abstract graph model: convert the substation topology into an abstract graph to describe the position relationship of each component and the fault propagation path; S4, short-circuit fault propagation modeling: using the multi-commodity flow model and the action logic of the protection device, simulate the propagation and removal process of the short-circuit fault when the protection device refuses to operate; The construction of the abstract graph model in S3 includes: S31, abstract graph conversion: convert the hub substation topology graph into an abstract graph, where the vertices of the abstract graph are the lines and nodes of the topology graph, and the edges of the abstract graph are the circuit breakers of the topology graph; S32, region division: the vertices of the topological graph are regarded as the same region, the same region represents the same operating state, and the circuit breaker divides the entire power system into multiple independent regions; S33, define protection scope and control logic: describe the configuration and fault isolation logic of the relay protection device in the abstract diagram.

2. The method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices according to claim 1 is characterized in that: The construction of the substation model and the configuration of the protection device and circuit breaker in S1 includes: S11, Hub substation classification: Hub substation is located at the hub point of the power system. The voltages of the high-voltage side, medium-voltage side and low-voltage side of the hub substation are 500kV, 220kV and 35kV respectively; S12, relay protection device configuration: The substation is equipped with relay protection devices for transmission lines and main equipment. The relay protection devices include transmission line protection, busbar protection and transformer protection. The relay protection configuration is configured according to the voltage level and wiring method of the substation.

3. The method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices according to claim 2 is characterized in that: The relay protection device configuration in S12 includes: S121, high voltage side wiring: The high voltage side of the hub substation adopts a one and a half circuit breaker wiring method; S122, transformer protection: The main protection of the transformer is longitudinal differential protection and heavy gas protection, and the backup protection adopts zero-sequence current protection, overcurrent protection and impedance protection; S123, transmission line protection: The main protection of the transmission line is the full-line fast-acting longitudinal protection, and the backup protection is distance protection and zero-sequence current protection; S124, busbar protection: busbar protection is busbar differential protection.

4. The method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices according to claim 3 is characterized in that: The short-circuit fault propagation mechanism under protection refusal defined in S2 includes: S21, protection device fails to operate: If the line protection device fails to operate, the short circuit fault will propagate to the hub substation through the closed circuit breaker; S22, fault propagation process: During the fault propagation process, it will affect the adjacent protection devices, causing the relay protection devices of the adjacent lines and equipment to trip the circuit breakers, thus expanding the scope of the power outage; S23, automatic reclosing: The automatic reclosing is performed on the principle of first reclosing the side circuit breaker and then the middle circuit breaker.

5. The method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices according to claim 4 is characterized in that: The definition of protection scope and control logic in S33 includes: S331, Vertex protection: In the abstract graph, each type of protection vertex is equipped with a corresponding relay protection device, and the protection range of the relay protection device is the range of the vertex and all its adjacent edges; S332, control logic: each edge is controlled by the relay protection devices of two adjacent vertices at the same time; S333, fault isolation: when there is a short circuit fault at the vertex, the corresponding relay protection device controls all circuit breakers around the vertex to operate to isolate the fault; S334, control in the event of failure: If the relay protection device of a vertex fails, the corresponding relay protection device cannot control the operation of the relevant circuit breakers. When the relay protection device of an adjacent vertex identifies a fault, the relay protection device of the adjacent vertex controls all circuit breakers around the vertex where the relay protection device fails to trip.

6. The method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices according to claim 5 is characterized in that: The short circuit fault propagation modeling in S4 includes: S41, short-circuit fault propagation process in phase A: Analyze the propagation path of the short-circuit fault when the relay protection device fails to operate, and describe the propagation state of the fault from the source vertex to each destination vertex and its impact through an abstract graph model; S42, Phase B short-circuit fault removal process: describes the action process of the relay protection device after identifying the short-circuit fault and analyzes the circuit breaker tripping logic.

7. A method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices according to claim 6, characterized in that: The short-circuit fault propagation process in phase A of S41 includes: S411, multi-commodity flow model: A multi-commodity flow model is used to represent the short-circuit fault propagation process in the abstract graph. The impact of the short-circuit fault is regarded as a commodity, the vertex that suffers effective physical attack is regarded as the commodity source, the edge is regarded as the path of the network flow, and all vertices are regarded as destinations. The commodity consumption of each destination is 0 or 1, representing the fault state of the vertex. The calculation formula is: in, is the edge state of stage A, E is the edge set of the abstract graph, is a continuous variable, is a binary variable representing whether node i has a short circuit fault, and V is the set of vertices in the abstract graph; S412, circuit breaker action logic: Since the circuit breaker is controlled by two protection devices at the same time, when one or both of the two adjacent vertices in the abstract graph have a short circuit fault, the circuit breaker connecting the two vertices will trip. The calculation formula is: S413, Sideline state constraint: Sideline state in phase A The constraints are expressed as: Among them, V T 、V L 、V B They are respectively the sets of transformer vertices, transmission line vertices, and busbar vertices in the abstract graph.

8. The method for modeling a short-circuit fault propagation model under failure of multiple relay protection devices according to claim 7 is characterized in that: The short-circuit fault removal process in stage B in S42 includes: S421, protection device action state: When the short-circuit fault in phase A propagates to the protection area of ​​the node, the relevant circuit breaker trips and isolates the fault. The calculation formula for the constraint of the protection device action state in phase B is: S422, circuit breaker tripping logic: determine the protection action status and the circuit breaker trip logic for phase B The constraint relationship is calculated as follows: S423, Final sideline status: Determine the final sideline status The constraint is calculated as follows:

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