Physical simulation method for monitoring insulation abnormity of PT / CT secondary circuit

Abstract

The invention discloses a physical simulation method for PT / CT secondary circuit insulation abnormity monitoring, and relates to the technical field of electrical variable measurement, and the method comprises the steps: setting two groups of PTs, setting a test point and a measurement system of a high-precision current transformer, and analyzing the insulation fault of PT secondary side N-phase two-point grounding; power is supplied to the simulation system through the power distribution area and a load is connected, so that the system runs with the load; the load is adjusted to be in a three-phase imbalance mode, so that the ABC three-phase current of the secondary side of the double-winding transformer T2 is unbalanced, and measurement and judgment are carried out; and outputting a final judgment result. When current measurement and data feature analysis are carried out, a waveform similarity analysis method based on the Hausdorff distance is adopted, and a fault branch can be accurately positioned when multiple points occur in the PT / CT secondary alternating current loop.

Description

Technical Field

[0001] The invention relates to the technical field of electrical variable measurement, and in particular to a physical simulation method for monitoring insulation anomaly of a PT / CT secondary circuit. Background Art

[0002] The PT secondary AC circuit and CT secondary AC circuit of the relay protection device are important components of the relay protection, involving voltage transformers, current transformers, local terminal boxes, outdoor cables, protection device terminals and acquisition circuits. They have the characteristics of complex wiring, many links, and hidden defects. As the scale of the power grid increases, the number of defects such as multi-point grounding, short circuit, and line break caused by insulation reasons in PT / CT secondary AC circuits continues to increase, which increases the probability of incorrect relay protection operation, seriously affecting the accuracy and reliability of relay protection equipment. When insulation abnormalities occur in the relay protection secondary AC circuit, the secondary protection device can judge some insulation abnormalities, but in most cases, such as: PT / CT secondary multi-point grounding, PT secondary N-phase line break and other problems, operation and maintenance personnel can only make analysis and judgments after the protection malfunctions.

[0003] When insulation abnormalities occur in the secondary AC circuit, such as multiple grounding of the N phases, the abnormal signal characteristics are not obvious during normal operation, and the data changes are often at the milliampere level. It can only be discovered through accident investigation after the relay protection device fails to operate correctly.

[0004] In order to solve this type of secondary AC circuit insulation abnormality or fault problem, the workload is large, a lot of manpower and material resources are consumed, and the inspection efficiency is low.

[0005] Under current circumstances, there is no good method for physical simulation analysis and judgment. It only relies on theoretical analysis and digital simulation calculations. If a high-voltage real model is used, the cost is too high and the area occupied is very large. At present, there is no physical simulation platform for secondary AC circuit insulation abnormalities. Summary of the invention

[0006] In view of the above existing problems, the present invention is proposed.

[0007] Therefore, the present invention provides a physical simulation method for monitoring insulation abnormalities in PT / CT secondary circuits, which can solve the existing insulation abnormality problem that the potential difference between the two grounding points of the primary grounding grid is low, or the two grounding points are close, and it is impossible to simply detect two-point or multi-point grounding by the current value.

[0008] In order to solve the above technical problems, the present invention provides the following technical solution, a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit, comprising: Set up two groups of PTs, test points and a high-precision current transformer measurement system to analyze the insulation fault of two-point grounding of the N phase on the secondary side of the PT; Power the simulation system through the distribution station area and connect the load to make the system run with load; Adjust the load to three-phase unbalanced mode to make the ABC three-phase current on the secondary side of the double-winding transformer T2 unbalanced, and measure and judge; Output the final judgment result.

[0009] As a preferred solution of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit described in the present invention, the measurement includes adjusting the load L to a three-phase unbalanced mode so that the ABC three-phase current on the secondary side of the dual-winding transformer T2 is unbalanced, thereby generating a zero-sequence current between the dual-winding transformer T1 and the dual-winding transformer T2.

[0010] As a preferred scheme of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit described in the present invention, the judgment includes measuring the effective value of the current of the N-phase grounding current sensor SCT1 on the secondary side of the PT when the test point is not grounded. If the effective value of the current is 0, it is marked as the first state.

[0011] As a preferred solution of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit described in the present invention, the judgment further includes, when the test point S is grounded, measuring the effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT, the effective current value of the N-phase current sensor SCT2 on the secondary side of the PT1, and the effective current value of the N-phase current sensor SCT3 on the secondary side of the PT2; If the measured current effective value of the N-phase grounding current sensor SCT1 on the secondary side of the PT is greater than the set high threshold, it is determined that two or more points of grounding of the N-phase have occurred and it is marked as the second state.

[0012] As a preferred solution of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit described in the present invention, the judgment further includes judging the relationship between the effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT, the effective current value of the N-phase current sensor SCT2 on the secondary side of the PT1, and the effective current value of the N-phase current sensor SCT3 on the secondary side of the PT2. The value of SCT1 should be equal to the value added to SCT2, and it is judged that the N-phase grounding fault occurs in PT1, which is marked as the third state. If the measured effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT is less than the set high threshold but greater than the set low threshold, it is determined whether two-point or multi-point grounding occurs.

[0013] As a preferred solution of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit described in the present invention, wherein: the determination of whether two-point or multi-point grounding occurs includes performing vector sum calculation on the increase value of SCT2 and the increase value of SCT3, and performing similarity analysis with the value of SCT1, and if the similarity is less than a set value, it is determined that two-point or multi-point grounding of N phases occurs; The value of SCT1 and the increase value of SCT2 are analyzed for similarity. If the similarity is less than the set value, it is determined that PT1 has N-phase grounding; The value of SCT1 and the increase value of SCT3 are analyzed for similarity. If the similarity is greater than the set value, it is determined that PT2 has no N-phase grounding.

[0014] As a preferred solution of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit described in the present invention, the similarity analysis includes a waveform similarity calculation method based on Hausdorff distance, assuming that SCT1, SCT2, and SCT3 take current values ​​in the same cycle according to the sampling frequency to form current point sets, which are respectively: , , , in, is the sampling current point set of one cycle of the N-phase grounding current sensor SCT1 on the secondary side of the PT, is the current sequence of the sampling points of SCT1 within the cycle; is the sampling current point set of one cycle of the N-phase grounding current sensor SCT2 on the secondary side of PT1, is the current sequence of the sampling points of SCT2 within the cycle; is the sampling current point set of one cycle of the N-phase grounding current sensor SCT3 on the secondary side of PT2, is the current sequence of the sampling points of SCT3 within a cycle.

[0015] As a preferred solution of the physical simulation method for monitoring insulation abnormality of PT / CT secondary circuit described in the present invention, wherein: the similarity analysis also includes: and The Hausdorff distance between is defined as: , in: , , In the formula, Represents the current point set measured by the current sensor SCT1 and the current point set measured by the current sensor SCT2 The Euclidian distance between two points, the point set A point in Arrival Set The distances of all points in are arranged in order of size, and the smallest value is recorded as di, then di is called the corresponding The minimum distance of All points The corresponding minimum distance di, the combination set is recorded as D, and the elements in D are arranged in order of size, among which the maximum value is , called point set arrive The one-way Hausdorff distance of the point set arrive One-way Hausdorff distance , The larger value of the two is used as the waveform similarity judgment; At the same time, the above is the distance between SCT1 and SCT2, and the distance between SCT1 and SCT3 is calculated in the same way.

[0016] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the processor implements the steps of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit.

[0017] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit.

[0018] Beneficial effects of the present invention: (1) For secondary AC circuit insulation faults, traditional methods mainly rely on theoretical calculations or digital simulations. The present invention uses physical simulations, which is more practical. (2) The simulation platform is effectively separated from the TNS power distribution system through an isolation transformer, and can simulate the direct grounding of large currents on site; (3) The physical simulation adopted by the present invention occupies a small area and is easy to simulate various secondary insulation faults; (4) When simulating insulation faults in practice, high-precision sensors are used for testing, data feature analysis, and analysis and judgment are performed to easily verify the feasibility of various algorithms.

[0019] (5) When the traditional method is used for detection, it mainly relies on the effective value of the current of each branch, which cannot fully guarantee the accuracy of locating the fault branch. When analyzing the data characteristics, the present invention adopts the waveform similarity analysis method to accurately locate the fault branch. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0021] Figure 1 A flow chart of a physical simulation method for monitoring insulation anomalies in a PT / CT secondary circuit is provided as an embodiment of the present invention.

[0022] Figure 2 A schematic diagram of the principle of a simulation platform for a physical simulation method for monitoring insulation anomalies in PT / CT secondary circuits provided by an embodiment of the present invention.

[0023] Figure 3 A schematic diagram of a simulation platform expansion of a physical simulation method for monitoring insulation anomalies in a PT / CT secondary circuit provided by an embodiment of the present invention.

[0024] Figure 4 A simulation platform for a physical simulation method for monitoring insulation abnormality in a PT / CT secondary circuit is provided in accordance with an embodiment of the present invention, and a PT secondary circuit N-phase two-point grounding test is performed. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] Example 1 Reference Figure 1 , Figure 4, which is the first embodiment of the present invention, provides a physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit, comprising: Set up two groups of PTs, test points and a high-precision current transformer measurement system to analyze the insulation fault of two-point grounding of the N phase on the secondary side of the PT; power the simulation system through the distribution station area and connect the load to make the system run with load; adjust the load to the three-phase unbalanced mode to make the ABC three-phase current on the secondary side of the double-winding transformer T2 unbalanced, and measure and judge; output the final judgment result.

[0028] The simulation platform can simulate and analyze various insulation anomalies in the PT / CT secondary AC circuit. The following is a specific description of the two-point grounding of the N-phase on the PT secondary side.

[0029] The test environment is built based on the physical simulation platform. In order to more comprehensively analyze the insulation fault of the two-point grounding of the N phase on the secondary side of the PT, two groups of PTs are set up, and test points and a high-precision current transformer measurement system are set up, such as Figure 4 shown.

[0030] The measurement and judgment include adjusting the load L to a three-phase unbalanced mode so that the ABC three-phase current on the secondary side of the double-winding transformer T2 is unbalanced, thereby generating a zero-sequence current between the double-winding transformer T1 and the double-winding transformer T2.

[0031] The measurement and judgment include measuring the effective value of the current of the N-phase grounding current sensor SCT1 on the secondary side of the PT (referring to the general term for PT1 and PT2) when the test point S is not grounded, and the value is 0 at this time.

[0032] The measurement and judgment also include grounding the test point S, measuring the effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT, the effective current value of the N-phase current sensor SCT2 on the secondary side of the PT1, and the effective current value of the N-phase current sensor SCT3 on the secondary side of the PT2; If the measured current effective value of the N-phase grounding current sensor SCT1 on the secondary side of the PT is greater than the set high threshold, it is determined that two or more points of grounding of the N-phase have occurred.

[0033] The measurement and judgment also includes further judging the relationship between the effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT, the effective current value of the N-phase current sensor SCT2 on the secondary side of the PT1, and the effective current value of the N-phase current sensor SCT3 on the secondary side of the PT2. The value of SCT1 should be equal to the value added to SCT2, and it is judged that the N-phase grounding fault occurs in PT1; If the measured current effective value of the N-phase grounding current sensor SCT1 on the secondary side of the PT is less than the set high threshold but greater than the set low threshold, it is necessary to further determine whether two-point or multi-point grounding occurs.

[0034] The measurement and judgment also includes performing vector sum calculation on the increase value of SCT2 and the increase value of SCT3, and performing similarity analysis with the value of SCT1. If the similarity is less than a set value, it is judged that two or more points of grounding of the N phases have occurred; The value of SCT1 and the increase value of SCT2 are analyzed for similarity. If the similarity is less than the set value, it is determined that PT1 has N-phase grounding; The value of SCT1 and the increase value of SCT3 are analyzed for similarity. If the similarity is greater than the set value, it is determined that PT2 has no N-phase grounding.

[0035] The similarity analysis includes a waveform similarity calculation method based on Hausdorff distance, assuming that SCT1, SCT2, and SCT3 take current values ​​in the same cycle according to the sampling frequency to form current point sets, which are respectively: , , , in, is the sampling current point set of one cycle of the N-phase grounding current sensor SCT1 on the secondary side of the PT, is the current sequence of the sampling points of SCT1 within the cycle; is the sampling current point set of one cycle of the N-phase grounding current sensor SCT2 on the secondary side of PT1, is the current sequence of the sampling points of SCT2 within the cycle; is the sampling current point set of one cycle of the N-phase grounding current sensor SCT3 on the secondary side of PT2, is the current sequence of the sampling points of SCT3 within a cycle.

[0036] The similarity analysis also includes: and The Hausdorff distance between is defined as: , in: , , In the formula, Represents the current point set measured by the current sensor SCT1 and the current point set measured by the current sensor SCT2 The Euclidian distance between two points, the point set A point in Arrival Set The distances of all points in are arranged in order of size, and the smallest value is recorded as di, then di is called the corresponding The minimum distance of All points The corresponding minimum distance di, the combination set is recorded as D, and the elements in D are arranged in order of size, among which the maximum value is , called point set arrive The one-way Hausdorff distance of the point set arrive One-way Hausdorff distance , The larger value of the two is used as the waveform similarity judgment; At the same time, the above is the distance between SCT1 and SCT2, and the distance between SCT1 and SCT3 is calculated in the same way.

[0037] Example 2 Reference Figure 2-Figure 3 , which is an embodiment of the present invention, provides a physical simulation platform for realizing PT / CT secondary AC circuit insulation abnormality monitoring. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0038] The physical simulation system platform comprises: Input side isolation transformer T1; 400V bus and analog circuit connected to the bus; the analog circuit includes a voltage transformer PT and a current transformer CT connected in sequence; output side isolation transformer T2; grounding system between the neutral points of the isolation transformer; RLC three-phase load system L Among them, the isolation transformer is star-connected, and the neutral point is directly grounded; the primary side of the input side isolation transformer is connected to the 400V side of the TNS system in the distribution station area.

[0039] according to Figure 2 The connection relationship between the various parts of the platform is as follows: The high voltage side of the input isolation transformer T1 is connected to the TNS system of the distribution station area; The low voltage side of the input side isolation transformer T1 and the high voltage side of the output side isolation transformer T2 are connected; The low voltage side of the output side isolation transformer T2 is connected to a three-phase RLC adjustable load L; The high and low voltage sides of the input side isolation transformer T1 are YY connected, with the neutral point grounded; The high and low voltage sides of the output side isolation transformer T2 are in YY connection mode, with the neutral point grounded; Single-phase voltage transformers are connected in parallel between the three phases ABC between the low-voltage side of the isolation transformer T1 on the input side and the high-voltage side of the isolation transformer T2 on the output side. The primary-side N-phase of the three single-phase voltage transformers is short-circuited to ground, and the secondary-side N-phase is short-circuited to ground. The secondary sides ABCN are connected to an analog measurement and control protection device. In the measurement and control protection device, the three-phase voltage is first converted into a small voltage through a small PT and then used by the measurement and control protection device.

[0040] Single-phase current transformers are connected in series between the low-voltage side of the input-side isolation transformer T1 and the high-voltage side of the output-side isolation transformer T2. The secondary sides of the three single-phase current transformers are grounded at one point and connected to an analog measurement and control protection device. The measurement and control protection device is connected to the three-phase current, which is first converted into a small voltage through a small CT and then used by the measurement and control protection device.

[0041] A high-precision current transformer is connected to the neutral line grounding point on the secondary side of the voltage transformer PT and the neutral line on the secondary side, and data is collected through an open-type high-precision micro current sensor.

[0042] A high-precision current transformer is connected to the neutral line grounding point on the secondary side of the current transformer CT and the neutral line on the secondary side, and data is collected through an open-type high-precision micro current sensor.

[0043] according to Figure 2 The platform can be further expanded to complete more functions: On the low-voltage 400V bus side of the input isolation transformer T1, multiple analog lines can be extended, such as Figure 3 shown.

[0044] according to Figure 2 Schematic diagram of the principle. The simulation platform isolates a simulation system from the TNS system in the distribution station area through a double-winding transformer T1, so that the platform can simulate actual high-current direct grounding conditions.

[0045] The working principle is: power is supplied to the simulation system through the distribution station area, and the load L is connected to make the system run under load. By adjusting the load L, the ABC three-phase load on the secondary side of the double-winding transformer T2 is unbalanced, thereby generating a zero-sequence current on the primary side of the double-winding transformer T2. The zero-sequence current flows through the secondary side grounding of the double-winding transformer T1 and the primary side grounding of the double-winding transformer T2, thereby generating a voltage difference, thereby simulating the substation grounding network.

[0046] The ABC three-phases on the secondary side of the double-winding transformer T1 and the ABC three-phases on the primary side of the double-winding transformer T2 are connected respectively, and a voltage transformer PT is connected in parallel and a current transformer CT is connected in series on the ABC three-phase line. The secondary sides of the PT and CT are connected to the measurement and control protection device, and the primary and secondary N phases of the PT and CT are grounded respectively. At this time, when the N phase on the secondary side of the PT / CT is grounded, there is no current at the grounding point because no loop is formed; if insulation faults such as two-point or multi-point grounding of the N phase on the secondary side of the PT / CT, phase grounding of the secondary side line of the PT / CT, and disconnection of the N phase on the secondary side of the PT / CT occur, the insulation fault can be determined through the measurement data and analysis of the grounding current, the secondary side voltage of the measurement and control device, etc.

[0047] Through the simulation platform, various insulation anomalies in the PT / CT secondary AC circuit can be simulated.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0049] Example 3 The third embodiment of the present invention is different from the first two embodiments in that: If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, RandomAccess Memory), disk or optical disk, etc., which can store program code.

[0050] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0051] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0052] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0053] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0054] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A physical simulation method for monitoring insulation abnormality of PT / CT secondary circuit, characterized in that: include, Set up two groups of PTs, test points and a high-precision current transformer measurement system to analyze the insulation fault of two-point grounding of the N phase on the secondary side of the PT; Power the simulation system through the distribution station area and connect the load to make the system run with load; Adjust the load to three-phase unbalanced mode to make the ABC three-phase current on the secondary side of the double-winding transformer T2 unbalanced, and measure and judge; Output the final judgment result.

2. A physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit according to claim 1, characterized in that: The measurement includes adjusting the load L to a three-phase unbalanced mode so that the ABC three-phase currents on the secondary side of the double-winding transformer T2 are unbalanced, thereby generating a zero-sequence current between the double-winding transformer T1 and the double-winding transformer T2.

3. A physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit according to claim 2, characterized in that: The determination includes, when the test point is not grounded, measuring the effective value of the current of the N-phase grounding current sensor SCT1 on the secondary side of the PT, and if the effective value of the current is 0, marking it as the first state.

4. A physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit according to claim 3, characterized in that: The determination further includes, when the test point S is grounded, measuring the effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT, the effective current value of the N-phase current sensor SCT2 on the secondary side of the PT1, and the effective current value of the N-phase current sensor SCT3 on the secondary side of the PT2; If the measured current effective value of the N-phase grounding current sensor SCT1 on the secondary side of the PT is greater than the set high threshold, it is determined that two or more points of grounding of the N-phase have occurred and it is marked as the second state.

5. A physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit according to claim 4, characterized in that: The determination further includes determining the relationship between the effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT, the effective current value of the N-phase current sensor SCT2 on the secondary side of the PT1, and the effective current value of the N-phase current sensor SCT3 on the secondary side of the PT2. The value of SCT1 should be equal to the value added to SCT2, and it is determined that the PT1 has an N-phase grounding fault, which is marked as the third state. If the measured effective current value of the N-phase grounding current sensor SCT1 on the secondary side of the PT is less than the set high threshold but greater than the set low threshold, it is determined whether two-point or multi-point grounding occurs.

6. A physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit according to claim 5, characterized in that: The determining whether two-point or multi-point grounding occurs includes performing vector sum calculation on the added value of SCT2 and the added value of SCT3, and performing similarity analysis with the value of SCT1. If the similarity is less than a set value, it is determined that two-point or multi-point grounding of the N phases occurs; The value of SCT1 and the increase value of SCT2 are analyzed for similarity. If the similarity is less than the set value, it is determined that PT1 has N-phase grounding; The value of SCT1 and the increase value of SCT3 are analyzed for similarity. If the similarity is greater than the set value, it is determined that PT2 has no N-phase grounding.

7. A physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit according to claim 6, characterized in that: The similarity analysis includes a waveform similarity calculation method based on Hausdorff distance, assuming that SCT1, SCT2, and SCT3 take current values ​​in the same cycle according to the sampling frequency to form current point sets, which are respectively: ， ， ， in, is the sampling current point set of one cycle of the N-phase grounding current sensor SCT1 on the secondary side of the PT, is the current sequence of the sampling points of SCT1 within the cycle; is the sampling current point set of one cycle of the N-phase grounding current sensor SCT2 on the secondary side of PT1, is the current sequence of the sampling points of SCT2 within the cycle; is the sampling current point set of one cycle of the N-phase grounding current sensor SCT3 on the secondary side of PT2, is the current sequence of the sampling points of SCT3 within a cycle.

8. A physical simulation method for monitoring insulation abnormality of a PT / CT secondary circuit according to claim 7, characterized in that: The similarity analysis also includes: and The Hausdorff distance between is defined as: ， in: ， ， In the formula, Represents the current point set measured by the current sensor SCT1 and the current point set measured by the current sensor SCT2 The Euclidian distance between two points, the point set A point in Arrival Set The distances of all points in are arranged in order of size, and the smallest value is recorded as di, then di is called the corresponding The minimum distance of All points The corresponding minimum distance di, the combination set is recorded as D, and the elements in D are arranged in order of size, among which the maximum value is , called point set arrive The one-way Hausdorff distance of the point set arrive One-way Hausdorff distance , The larger value of the two is used as the waveform similarity judgment; At the same time, the above is the distance between SCT1 and SCT2, and the distance between SCT1 and SCT3 is calculated in the same way.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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