Method and system for identifying fault mode of sheath grounding of cross-connected high-voltage cables

Abstract

The present invention relates to a method and system for identifying a cross-connected high-voltage cable sheath grounding fault mode, the method comprising determining a circuit transfer function of a corresponding type of grounding fault according to an equivalent circuit model of different types of sheath grounding faults; determining fault characteristic quantities of different types of sheath grounding faults and calculating the range of fault characteristic quantities, and constructing a typical fault mode classification table; establishing a K-means clustering model, clustering the fault characteristic quantities, and obtaining clustering results; acquiring a detection signal of a target high-voltage cable, calculating a target fault characteristic quantity of the target high-voltage cable, and determining the fault type of the target high-voltage cable. Establishing a typical sheath grounding fault equivalent circuit model and determining the corresponding circuit transfer function, then extracting the fault characteristic quantity and constructing a typical fault mode classification table, performing cluster analysis through the K-means clustering model, the target high-voltage cable can be identified according to the clustering results, and its fault type can be obtained, thereby improving the diagnostic accuracy of the sheath grounding fault.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage cable fault detection, and in particular to a method for identifying a cross-connected high-voltage cable sheath grounding fault mode. Background Art

[0002] High-voltage cables are usually laid underground by direct burial or cable trenching. During long-term service, weak links such as external insulation and grounding boxes will age and deteriorate under the influence of moisture and soil environmental factors, resulting in sheath grounding faults. At present, there are seven typical fault modes of cross-connected high-voltage cable sheath grounding that have been discovered: sheath protector breakdown, outer sheath damage and low-resistance grounding, water ingress to the grounding box, loose welding of sheath and grounding, theft of grounding wires, epoxy board breakdown, and wrong wiring of cross-connected grounding boxes. Existing sheath grounding fault pattern recognition methods do not cover the seven fault types and have low recognition accuracy. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method and system for identifying a grounding fault mode of a cross-connected high-voltage cable sheath in view of the above-mentioned deficiencies in the prior art.

[0004] The technical solution of the present invention to solve the above technical problem is as follows: A method for identifying a cross-connected high-voltage cable sheath grounding fault mode comprises the following steps:

[0005] According to the equivalent circuit model of different types of sheath grounding faults of high-voltage cables, the circuit transfer function of the corresponding type of grounding fault is determined;

[0006] Determine the fault characteristic quantities of different types of sheath grounding faults, calculate the range of the fault characteristic quantities according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and construct a typical fault mode classification table;

[0007] A K-means clustering model is established, and the fault characteristic quantities of different types of sheath grounding faults are clustered to obtain clustering results of different types of sheath grounding faults.

[0008] A detection signal of a target high-voltage cable is acquired, a target fault feature quantity of the target high-voltage cable is calculated, and a fault type of the target high-voltage cable is determined based on the target fault feature quantity and the clustering result.

[0009] The beneficial effects of the present invention are as follows: the method for identifying the fault mode of the sheath grounding of a cross-connected high-voltage cable of the present invention establishes an equivalent circuit model for each typical sheath grounding fault, determines the corresponding circuit transfer function, extracts the fault characteristic quantity and constructs a typical fault mode classification table, and performs cluster analysis through a K-means clustering model, so that the target high-voltage cable can be identified according to the clustering results to obtain its fault type, thereby greatly improving the diagnostic accuracy of the sheath grounding fault and improving the maintenance efficiency of the sheath protector.

[0010] On the basis of the above technical solution, the present invention can also be improved as follows:

[0011] Further: the circuit transfer function of the corresponding type of grounding fault is determined according to the equivalent circuit model of the different types of sheath grounding faults of the high-voltage cable, specifically including:

[0012] The equivalent circuit models of different types of grounding faults are established, and the capacitive current of the sheath loop is calculated according to the sheath current values ​​of the two grounding points of the same sheath loop;

[0013] Among them, the three-phase high-voltage cable is divided into nine sections A1, A2, A3, B1, B2, B3, C1, C2, C3, and current transformers S1, S2, S3, S4, S5, S6 are installed at both ends of the three-phase high-voltage cable respectively;

[0014] The circuit transfer function of the corresponding type of sheath grounding fault calculated according to the capacitive current is specifically:

[0015] 1) Normal grounding of the sheath: The difference in sheath current between the two direct grounding points is the capacitive current. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0016]

[0017] in, is the sheath current value at the current transformer S1; is the sheath current value at current transformer S4; They are the leakage currents of segments A1, B2, and C3 respectively;

[0018] 2) Low-resistance grounding fault caused by damaged outer sheath: The induced current is divided into two loops. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0019]

[0020] in, is the induced electromotive force on the left side of the fault point in the metal sheath of section A1; is the induced electromotive force on the right side of the fault point in the metal sheath of section A1; They are the induced electromotive force of the metal sheaths of sections B2 and C3 in the A1-B2-C3 loop; are the leakage currents in segments A1, B2, and C3, respectively, and R S is the fault impedance from the fault point to the ground, and R is the ground impedance;

[0021] 3) Sheath protector breakdown fault: The induced current is divided into two loops. The circuit transfer function is constructed according to the current difference detected by current transformer S1 and current transformer S4 as follows:

[0022]

[0023] in, are the induced electromotive force of the metal sheaths of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z L1 is the fault impedance of the fault sheath protector L1 to the ground, and R is the ground impedance;

[0024] 4) Epoxy board breakdown failure: A1-B2-C3 loop and B1-C2-A3 loop are short-circuited. The transfer functions are constructed according to the current difference of A1-B2-C3 loop and B1-C2-A3 loop as follows:

[0025]

[0026]

[0027] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, is the induced electromotive force of the metal sheath of sections B1, C2, and A3 in the B1-C2-A3 loop, are the leakage currents in segments A1, B2, and C3 respectively, R is the ground impedance; R is the ground impedance;

[0028] 5) Water ingress failure in the grounding box: The three circuits are short-circuited, and the circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0029]

[0030] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z mA1 , Z mB2 , Z mC3is the impedance of the metal sheath of sections A1, B2, and C3 in the A1-B2-C3 loop, and R is the ground impedance;

[0031] 6) Loose sheath welding point fault: The sheath circuit is open. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0032]

[0033] 7) Ground wire theft fault: The sheath is open to the ground. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0034]

[0035] 8) Sheath connection error fault: The transfer function is constructed based on the single-point sheath current at the beginning and end of the three loops as follows:

[0036]

[0037]

[0038]

[0039] in, is the sheath current value at the current transformer S1~S6; The induced electromotive force of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively. are the leakage currents of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2, and C3, respectively, mA1 , Z mA2 , Z mA3 , Z mB1 , Z mB2 , Z mB3 , Z mC1 , Z mC2 , Z mC3 They are the impedances of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively.

[0040] The beneficial effect of the above further scheme is: the capacitive current of the sheath loop is accurately calculated through the equivalent circuit model, and then the circuit transfer function of the corresponding type of sheath grounding fault can be accurately calculated based on the capacitive current, so that the fault characteristic quantity range can be calculated according to the circuit transfer function in the subsequent step to accurately construct a fault mode classification table.

[0041] Further: the determination of the fault characteristic quantities of different types of sheath grounding faults, and the calculation of the fault characteristic quantity range according to the circuit transfer function and the detection signal of the sheath grounding fault, and the construction of a typical fault mode classification table specifically include the following steps:

[0042] The vector difference phase angle of sheath current is used as the fault characteristic quantity, and the fault mode of different types of sheath grounding faults is coded;

[0043] Calculating the fault characteristic range corresponding to the type of sheath grounding fault according to the circuit transfer function;

[0044] A typical failure mode classification table is constructed according to the failure mode codes, failure characteristic quantities and failure characteristic quantity ranges.

[0045] The beneficial effect of the above further scheme is: by using the vector difference phase angle of the sheath current as the fault characteristic quantity, the fault characteristic quantity range corresponding to the sheath grounding fault type can be directly calculated according to the circuit transfer function, and combined with the fault mode coding, a typical fault mode classification table can be constructed more conveniently.

[0046] Further: the establishment of the K-means clustering model and clustering of fault feature quantities of different types of sheath grounding faults to obtain clustering results of different types of sheath grounding faults specifically includes the following steps:

[0047] Establish a K-means clustering model and generate a random sample set x i As the initial clustering sample, any sample x in the actual sampling is calculated based on the fault mode coding and belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), then the total probability calculation formula is:

[0048]

[0049] Among them, θ k =[θ0,θ1,θ2,θ3,θ4,θ5,θ6,θ7] is a parameter vector, which represents the phase angle of the sheath current phasor difference;

[0050] According to the actual sample phase difference phase angle θ k The initial phase difference angle θ in the fault mode classification table x The ratio of the conditional probability P(x|ω k ,θ k ), the calculation formula is:

[0051]

[0052] Taking the variation range of the fault characteristic quantity as the initial reference quantity, the mean vector μ corresponding to normal sheath grounding and different types of sheath grounding faults is set. i As the initial clustering core, 0≤i≤N, N is the total number of samples, calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , and classify it as the cluster where the core of the cluster with the smallest Euclidean distance is located. The calculation formula is:

[0053]

[0054] The Euclidean distance of the probability between the actual sample x and the initial sample is defined as:

[0055]

[0056] Among them, j is the number of samples in the cluster;

[0057] The point closest to the average distance of each cluster is selected as the new cluster core, and the above clustering steps are repeated until the cluster core and cluster no longer change, and the clustering results of different types of sheath grounding faults are obtained.

[0058] The beneficial effect of the above further solution is: by calculating whether any sample x belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), and calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , so as to conduct cluster analysis and obtain the final clustering results.

[0059] Further: the step of determining the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result specifically includes the following steps:

[0060] respectively calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding;

[0061] When the probability density between the target fault feature and one type of sheath grounding fault is the largest, determining the sheath grounding fault type with the largest probability density between the target fault feature as the fault type of the target high-voltage cable;

[0062] When the probability density between the target fault characteristic quantity and the normal grounding of the sheath is the largest, the unprotected grounding fault of the target high-voltage cable is determined.

[0063] The beneficial effect of the above further scheme is: by calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding, it can be determined that the maximum value of the probability density corresponds to normal sheath grounding or a certain type of sheath grounding fault, so as to finally realize the identification of the type of sheath grounding fault.

[0064] The present invention also provides a method for identifying a cross-connected high-voltage cable sheath grounding fault mode, comprising: a circuit transfer function module, a classification table construction module, a clustering module and a calculation identification module;

[0065] The circuit transfer function module is used to determine the circuit transfer function of the corresponding type of grounding fault according to the equivalent circuit model of different types of sheath grounding faults of the high-voltage cable;

[0066] The classification table building module is used to determine the fault characteristic quantities of different types of sheath grounding faults, and calculate the fault characteristic quantity range according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and build a typical fault mode classification table;

[0067] The clustering module is used to establish a K-means clustering model and cluster the fault feature quantities of different types of sheath grounding faults to obtain clustering results of different types of sheath grounding faults;

[0068] The calculation and identification module is used to obtain the detection signal of the target high-voltage cable, calculate the target fault feature quantity of the target high-voltage cable, and determine the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result.

[0069] The cross-connected high-voltage cable sheath grounding fault mode identification system of the present invention establishes equivalent circuit models for typical sheath grounding faults, determines corresponding circuit transfer functions, extracts fault characteristic quantities, constructs a typical fault mode classification table, and performs cluster analysis through a K-means clustering model. In this way, the target high-voltage cable can be identified according to the clustering results to obtain its fault type, thereby greatly improving the diagnostic accuracy of sheath grounding faults and improving the maintenance efficiency of sheath protectors.

[0070] On the basis of the above technical solution, the present invention can also be improved as follows:

[0071] Further: the circuit transfer function module is specifically used for:

[0072] The equivalent circuit models of different types of grounding faults are established, and the capacitive current of the sheath loop is calculated according to the sheath current values ​​of the two grounding points of the same sheath loop;

[0073] Among them, the three-phase high-voltage cable is divided into nine sections A1, A2, A3, B1, B2, B3, C1, C2, C3, and current transformers S1, S2, S3, S4, S5, S6 are installed at both ends of the three-phase high-voltage cable respectively;

[0074] The circuit transfer function of the corresponding type of sheath grounding fault calculated according to the capacitive current is specifically:

[0075] 1) Normal grounding of the sheath: The difference in sheath current between the two direct grounding points is the capacitive current. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0076]

[0077] in, is the sheath current value at the current transformer S1; is the sheath current value at current transformer S4; They are the leakage currents of segments A1, B2, and C3 respectively;

[0078] 2) Low-resistance grounding fault caused by damaged outer sheath: The induced current is divided into two loops. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0079]

[0080] in, is the induced electromotive force on the left side of the fault point in the metal sheath of section A1; is the induced electromotive force on the right side of the fault point in the metal sheath of section A1; They are the induced electromotive force of the metal sheaths of sections B2 and C3 in the A1-B2-C3 loop; are the leakage currents in segments A1, B2, and C3, respectively, and R S is the fault impedance from the fault point to the ground, and R is the ground impedance;

[0081] 3) Sheath protector breakdown fault: The induced current is divided into two loops. The circuit transfer function is constructed according to the current difference detected by current transformer S1 and current transformer S4 as follows:

[0082]

[0083] in, are the induced electromotive force of the metal sheaths of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z L1 is the fault impedance of the fault sheath protector L1 to the ground, and R is the ground impedance;

[0084] 4) Epoxy board breakdown failure: A1-B2-C3 loop and B1-C2-A3 loop are short-circuited. The transfer functions are constructed according to the current difference of A1-B2-C3 loop and B1-C2-A3 loop as follows:

[0085]

[0086]

[0087] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, is the induced electromotive force of the metal sheath of sections B1, C2, and A3 in the B1-C2-A3 loop, are the leakage currents in segments A1, B2, and C3 respectively, R is the ground impedance; R is the ground impedance;

[0088] 5) Water ingress failure in the grounding box: The three circuits are short-circuited, and the circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0089]

[0090] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z mA1 , Z mB2 , Z mC3 is the impedance of the metal sheath of sections A1, B2, and C3 in the A1-B2-C3 loop, and R is the ground impedance;

[0091] 6) Loose sheath welding point fault: The sheath circuit is open. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0092]

[0093] 7) Ground wire theft fault: The sheath is open to the ground. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0094]

[0095] 8) Sheath connection error fault: The transfer function is constructed based on the single-point sheath current at the beginning and end of the three loops as follows:

[0096]

[0097]

[0098]

[0099] in, is the sheath current value at the current transformer S1~S6; The induced electromotive force of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively. are the leakage currents of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2, and C3, respectively, mA1 , Z mA2 , Z mA3 , Z mB1 , Z mB2 , Z mB3 , Z mC1 , Z mC2 , Z mC3 They are the impedances of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively.

[0100] The beneficial effect of the above further scheme is: the capacitive current of the sheath loop is accurately calculated through the equivalent circuit model, and then the circuit transfer function of the corresponding type of sheath grounding fault can be accurately calculated based on the capacitive current, so that the fault characteristic quantity range can be calculated according to the circuit transfer function in the subsequent step to accurately construct a fault mode classification table.

[0101] Further: the classification table construction module is specifically used for:

[0102] The vector difference phase angle of sheath current is used as the fault characteristic quantity, and the fault mode of different types of sheath grounding faults is coded;

[0103] Calculating the fault characteristic range corresponding to the type of sheath grounding fault according to the circuit transfer function;

[0104] A typical failure mode classification table is constructed according to the failure mode codes, failure characteristic quantities and failure characteristic quantity ranges.

[0105] The beneficial effect of the above further scheme is: by using the vector difference phase angle of the sheath current as the fault characteristic quantity, the fault characteristic quantity range corresponding to the sheath grounding fault type can be directly calculated according to the circuit transfer function, and combined with the fault mode coding, a typical fault mode classification table can be constructed more conveniently.

[0106] Further: the clustering module is specifically used for:

[0107] Establish a K-means clustering model and generate a random sample set x iAs the initial clustering sample, any sample x in the actual sampling is calculated based on the fault mode coding and belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), then the total probability calculation formula is:

[0108]

[0109] Among them, θ k =[θ0,θ1,θ2,θ3,θ4,θ5,θ6,θ7] is a parameter vector, which represents the phase angle of the sheath current phasor difference;

[0110] According to the actual sample phase difference phase angle θ k The initial phase difference angle θ in the fault mode classification table x The ratio of the conditional probability P(x|ω k ,θ k ), the calculation formula is:

[0111]

[0112] Taking the variation range of the fault characteristic quantity as the initial reference quantity, the mean vector μ corresponding to normal sheath grounding and different types of sheath grounding faults is set. i As the initial clustering core, 0≤i≤N, N is the total number of samples, calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , and classify it as the cluster where the core of the cluster with the smallest Euclidean distance is located. The calculation formula is:

[0113]

[0114] The Euclidean distance of the probability between the actual sample x and the initial sample is defined as:

[0115]

[0116] Among them, j is the number of samples in the cluster;

[0117] Select the point closest to the average distance of each cluster as the new cluster core, and repeat the above clustering steps until the cluster core and cluster no longer change, and obtain the clustering results of different types of sheath grounding faults;

[0118] The beneficial effect of the above further solution is: by calculating whether any sample x belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), and calculate the random sample set x iWith all mean vectors μ i The Euclidean distance μ between i , so as to conduct cluster analysis and obtain the final clustering results.

[0119] Further: The specific implementation of the calculation and identification module determining the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result is:

[0120] Calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding respectively;

[0121] When the probability density between the target fault feature and one type of sheath grounding fault is the largest, determining the sheath grounding fault type with the largest probability density between the target fault feature as the fault type of the target high-voltage cable;

[0122] When the probability density between the target fault characteristic quantity and the normal grounding of the sheath is the largest, the unprotected grounding fault of the target high-voltage cable is determined.

[0123] The beneficial effect of the above further scheme is: by calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding, it can be determined that the maximum value of the probability density corresponds to normal sheath grounding or a certain type of sheath grounding fault, so as to finally realize the identification of the type of sheath grounding fault.

[0124] The present invention provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the steps of the method are implemented.

[0125] The present invention also provides a semi-supervisory identification device for cross-connected high-voltage cable sheath grounding fault mode, comprising the storage medium and a processor, wherein the processor implements the steps of the method when executing the computer program on the storage medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0126] Figure 1 A schematic flow chart of a method for identifying a cross-connected high-voltage cable sheath grounding fault mode according to an embodiment of the present invention;

[0127] Figure 2 A schematic diagram of a cross-connected high-voltage cable line according to an embodiment of the present invention;

[0128] Figure 3 It is a schematic diagram of an equivalent circuit of a normal grounding of a sheath of a cross-connected high-voltage cable according to an embodiment of the present invention;

[0129] Figure 4 It is a schematic diagram of an equivalent circuit of a low-resistance grounding fault caused by damage to the outer sheath of a cross-connected high-voltage cable according to an embodiment of the present invention;

[0130] Figure 5 It is a schematic diagram of an equivalent circuit of a breakdown fault of a cross-connected high-voltage cable sheath protector according to an embodiment of the present invention;

[0131] Figure 6 It is a schematic diagram of an equivalent circuit of a breakdown fault of an epoxy board of a cross-connected high-voltage cable according to an embodiment of the present invention;

[0132] Figure 7 It is a schematic diagram of an equivalent circuit of a water inflow fault in a cross-connected high-voltage cable grounding box according to an embodiment of the present invention;

[0133] Figure 8 It is a schematic diagram of an equivalent circuit of a loose solder joint fault of a cross-connected high-voltage cable sheath according to an embodiment of the present invention;

[0134] Fig. 9 It is a schematic diagram of an equivalent circuit of a cross-connected high-voltage cable ground wire theft fault according to an embodiment of the present invention;

[0135] Fig.10 It is a schematic diagram of an equivalent circuit of a cross-connected high-voltage cable sheath connection error fault according to an embodiment of the present invention;

[0136] Fig.11 A schematic diagram of clustering results of different types of sheath grounding faults according to an embodiment of the present invention;

[0137] Fig.12 The present invention is a schematic structural diagram of a system for identifying a cross-connected high-voltage cable sheath grounding fault mode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0138] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0139] like Figure 1 As shown, a method for identifying a cross-connected high-voltage cable sheath grounding fault mode comprises the following steps:

[0140] According to the equivalent circuit model of different types of sheath grounding faults of high-voltage cables, the circuit transfer function of the corresponding type of grounding fault is determined;

[0141] Determine the fault characteristic quantities of different types of sheath grounding faults, calculate the range of the fault characteristic quantities according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and construct a typical fault mode classification table;

[0142] A K-means clustering model is established, and the fault characteristic quantities of different types of sheath grounding faults are clustered to obtain the clustering results of different types of sheath grounding faults.

[0143] A detection signal of a target high-voltage cable is acquired, a target fault feature quantity of the target high-voltage cable is calculated, and a fault type of the target high-voltage cable is determined based on the target fault feature quantity and the clustering result.

[0144] The method for identifying the sheath grounding fault mode of a cross-connected high-voltage cable of the present invention establishes equivalent circuit models for typical sheath grounding faults, determines the corresponding circuit transfer functions, extracts fault characteristic quantities, constructs a typical fault mode classification table, and performs cluster analysis through a K-means clustering model. In this way, the target high-voltage cable can be identified according to the clustering results to obtain its fault type, thereby greatly improving the diagnostic accuracy of the sheath grounding fault and improving the maintenance efficiency of the sheath protector.

[0145] In order to suppress the power frequency induced voltage, high-voltage cables over 1.2 kilometers are generally grounded by cross-connection. Figure 2 The three-phase high voltage cable is composed of multiple cross-interconnected sections as shown, and the three-phase high voltage cable is divided into nine sections A1, A2, A3, B1, B2, B3, C1, C2, and C3. Current transformers S1, S2, S3, S4, S5, and S6 are installed at both ends of the three-phase high voltage cable respectively.

[0146] Before actual measurement, the fault type and fault impedance are unknown, the known quantities are the cable capacitance current and the sheath impedance, and the detection quantity is the sheath current at multiple points. The present invention converts the equivalent circuit model of the high-voltage cable grounding system of the measured object into a transfer function between the grounding fault impedance and the detection quantity, and then distinguishes seven typical faults according to the transfer function between the fault impedance and the detection quantity. Figure 3-10 The circuit shown is symmetrical. This invention takes the A1-B2-C3 loop as an example to introduce the transfer functions of seven typical faults. The transfer functions of the other two loops are the same as A1-B2-C3. Only the component parameters need to be set according to the actual situation. The sensors corresponding to the A1-B2-C3 loop are S1 and S4, the sensors corresponding to the B1-C2-A3 loop are S2 and S5, and the sensors corresponding to the C1-A2-B3 loop are S3 and S6. Figure 3-10 As shown, there are equivalent circuit diagrams of normal sheath grounding, outer sheath damaged low-resistance grounding fault, sheath protector breakdown fault, epoxy board breakdown fault, grounding box water ingress fault, sheath solder joint loosening fault, grounding wire theft fault and sheath connection error fault.

[0147] The sheath current of the cross-connected high-voltage cable is the superposition of the capacitive current component and the inductive coupling current component. If the sheath-to-ground or sheath connection relationship changes, the electrostatic coupling and electromagnetic coupling relationship between the core and the sheath loop will change. Therefore, the sheath current difference between the two sheath current monitoring points in the same sheath loop can be used as a fault criterion. To facilitate the distinction of fault types, the sheath topology of the high-voltage cable in normal and fault conditions is coded from 0 to 7. The transfer function of the circuit topology under each fault is introduced below.

[0148] In one or more embodiments of the present invention, determining the circuit transfer function of the corresponding type of grounding fault according to the equivalent circuit model of different types of sheath grounding faults of the high-voltage cable specifically includes:

[0149] The equivalent circuit models of different types of grounding faults are established, and the capacitive current of the sheath loop is calculated according to the sheath current values ​​of the two grounding points of the same sheath loop;

[0150] The circuit transfer function of the corresponding type of sheath grounding fault calculated according to the capacitive current is specifically:

[0151] 1) The sheath is normally grounded, and the fault mode code is 0, such as Figure 3 As shown, since the two direct grounding points are in the same sheath loop, the induced current is the same, and the difference in sheath current between the two direct grounding points is the capacitive current. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0152]

[0153] in, is the sheath current value at the current transformer S1; is the sheath current value at current transformer S4; They are the leakage currents of segments A1, B2, and C3 respectively;

[0154] 2) Outer sheath damage low resistance grounding fault, the fault mode code is 1, such as Figure 4 As shown in the figure, the short circuit of the single sheath loop to ground is equivalent to adding a grounding point to the sheath. In the case of a low-resistance grounding fault caused by outer sheath damage, the capacitive current adds a grounding point. The induced current is divided into two loops. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0155]

[0156] in, is the induced electromotive force on the left side of the fault point in the metal sheath of section A1; is the induced electromotive force on the right side of the fault point in the metal sheath of section A1; They are the induced electromotive force of the metal sheaths of sections B2 and C3 in the A1-B2-C3 loop; are the leakage currents in segments A1, B2, and C3, respectively, and R S is the fault impedance from the fault point to the ground, and R is the ground impedance;

[0157] 3) Sheath protector breakdown failure, the failure mode code is 2, such as Figure 5 As shown in the figure, the short circuit of the single sheath loop to ground is equivalent to adding a grounding point to the sheath. In the case of a breakdown fault of the sheath protector, the capacitive current adds a grounding point, and the induced current is divided into two loops. The circuit transfer function is constructed according to the current difference detected by the current transformer S1 and the current transformer S4 as follows:

[0158]

[0159] in, are the induced electromotive force of the metal sheaths of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z L1 is the fault impedance of the fault sheath protector L1 to the ground, and R is the ground impedance;

[0160] 4) Epoxy board breakdown failure, the failure mode code is 3, such as Figure 6 As shown, the short circuit between the two sheath loops is equivalent to a low impedance in series between the two sheath loops. The epoxy board breakdown failure occurs in the cross-connected grounding box on the left, causing the A1-B2-C3 loop and the B1-C2-A3 loop to be short-circuited. The transfer functions constructed according to the current difference between the A1-B2-C3 loop and the B1-C2-A3 loop are as follows:

[0161]

[0162]

[0163] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, is the induced electromotive force of the metal sheath of sections B1, C2, and A3 in the B1-C2-A3 loop, are the leakage currents in segments A1, B2, and C3 respectively, R is the ground impedance; R is the ground impedance;

[0164] 5) The grounding box has water ingress fault, and the fault mode code is 4, such as Figure 7 As shown, the short circuit of the three-sheath circuit to ground is equivalent to the short circuit between the three-sheath circuits. In the case of water inflow failure in the grounding box, it represents the sewage short-circuiting the three circuits. The circuit transfer function is constructed according to the current difference detected by the current transformer S1 and the current transformer S4 as follows:

[0165]

[0166] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z mA1 , Z mB2 , Z mC3 is the impedance of the metal sheath of sections A1, B2, and C3 in the A1-B2-C3 loop, and R is the ground impedance;

[0167] 6) The sheath solder joint is loose, and the fault mode code is 5, such as Figure 8 As shown in the figure, the loosening of the sheath welding point is equivalent to an open circuit of the sheath loop, and the other two sheath loops form a loop with the ground, and the sheath loops are open. The circuit transfer function is constructed according to the current difference detected by the current transformer S1 and the current transformer S4 as follows:

[0168]

[0169] 7) Ground wire theft fault, fault mode code is 6, such as Fig. 9 As shown, the ground wire is stolen, which is equivalent to a sheath loop being open to the ground, short-circuited with the other three sheath loops, and the sheath is open to the ground. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0170]

[0171] 8) Sheath connection error fault, the fault mode code is 7, such as Fig.10 As shown in the figure, the sheath connection error is the transposition wiring error of the three circuits at the cross-connection grounding box, which makes it impossible to form a triangle connection and the induced voltage of the three phases cannot be offset. The common incorrect wiring method of "two left strokes and one right stroke" is used between the first and second sections of the cross-connection line, and "two right strokes and one left stroke" is used between the second and third sections. The transfer functions are constructed according to the single-point sheath currents at the beginning and end of the three circuits as follows:

[0172]

[0173]

[0174]

[0175] in, is the sheath current value at the current transformer S1~S6; The induced electromotive force of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively. are the leakage currents of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2, and C3, respectively, mA1 , Z mA2 , Z mA3 , Z mB1 , Z mB2 , Z mB3 , Z mC1 , Z mC2 , Z mC3 They are the impedances of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively.

[0176] The capacitive current of the sheath loop is accurately calculated through the equivalent circuit model, and then the circuit transfer function of the corresponding type of sheath grounding fault can be accurately calculated based on the capacitive current, so that the fault characteristic quantity range can be calculated according to the circuit transfer function to accurately construct a fault mode classification table.

[0177] In one or more embodiments of the present invention, the steps of determining the fault characteristic quantities of different types of sheath grounding faults, calculating the range of the fault characteristic quantities according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and constructing a typical fault mode classification table specifically include the following steps:

[0178] The vector difference phase angle of the sheath current is used as the fault characteristic quantity, and the fault mode coding is performed for different types of sheath grounding faults. The fault mode coding is as described above. Normal sheath grounding is 0, and the rest of the sheath grounding faults are divided into 1-7. The coding table is shown in Table 1 below:

[0179] Table 1

[0180] Failure Mode Circuit topology Fault feature quantity Failure mode coding Outer sheath damaged, low resistance grounding Single sheath loop grounding short circuit Phase difference angle k＝1 Sheath protector breakdown Single sheath loop grounding short circuit Phase difference angle k＝2 Epoxy board breakdown Short circuit between two sheath circuits Phase difference angle k＝3 Water ingress into grounding box Three-layer circuit short circuit Phase difference angle k＝4 Loosening of sheath welding points Open circuit between sheaths Phase difference angle k＝5 Ground wire stolen Sheath open to ground Phase difference angle k＝6 Sheath connection error Sheath triangle connection error Phase difference angle k＝7

[0181] Calculating the fault characteristic range corresponding to the type of sheath grounding fault according to the circuit transfer function;

[0182] A typical fault mode classification table is constructed according to the fault mode coding, fault characteristic quantity and fault characteristic quantity range, as shown in Table 2 below:

[0183] Table 2

[0184]

[0185]

[0186] By using the vector difference phase angle of the sheath current as the fault characteristic quantity, the fault characteristic quantity range corresponding to the sheath grounding fault type can be directly calculated according to the circuit transfer function, and a typical fault mode classification table can be conveniently constructed in combination with the fault mode coding.

[0187] In one or more embodiments of the present invention, the step of establishing a K-means clustering model and clustering the fault feature quantities of different types of sheath grounding faults to obtain clustering results of different types of sheath grounding faults specifically includes the following steps:

[0188] Establish a K-means clustering model and generate a random sample set x i As the initial clustering sample, any sample x in the actual sampling is calculated based on the fault mode coding and belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), then the total probability calculation formula is:

[0189]

[0190] Among them, θ k =[θ0,θ1,θ2,θ3,θ4,θ5,θ6,θ7] is a parameter vector, which represents the phase angle of the sheath current phasor difference;

[0191] According to the actual sample phase difference phase angle θ k The initial phase difference angle θ in the fault mode classification table x The ratio of the conditional probability P(x|ω k ,θ k ), the calculation formula is:

[0192]

[0193] Taking the variation range of the fault characteristic quantity as the initial reference quantity, the mean vector μ corresponding to normal sheath grounding and different types of sheath grounding faults is set. i As the initial clustering core, 0≤i≤N, N is the total number of samples, calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , and classify it as the cluster where the core of the cluster with the smallest Euclidean distance is located. The calculation formula is:

[0194]

[0195] The Euclidean distance of the probability between the actual sample x and the initial sample is defined as:

[0196]

[0197] Among them, j is the number of samples in the cluster;

[0198] Select the point closest to the average distance of each cluster as the new cluster core, and repeat the above clustering steps until the cluster core and cluster no longer change, and obtain the clustering results of different types of sheath grounding faults, such as Fig.11 shown.

[0199] By calculating whether any sample x belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), and calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , so as to conduct cluster analysis and obtain the final clustering results.

[0200] In one or more embodiments of the present invention, determining the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result specifically includes the following steps:

[0201] respectively calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding;

[0202] When the probability density between the target fault feature and one type of sheath grounding fault is the largest, determining the sheath grounding fault type with the largest probability density between the target fault feature as the fault type of the target high-voltage cable;

[0203] When the probability density between the target fault characteristic quantity and the normal grounding of the sheath is the largest, the unprotected grounding fault of the target high-voltage cable is determined.

[0204] By calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding, it can be determined that the maximum probability density corresponds to normal sheath grounding or one of the types of sheath grounding faults, so as to finally realize the identification of the type of sheath grounding fault.

[0205] like Fig.12 As shown, the present invention also provides a method for identifying a cross-connected high-voltage cable sheath grounding fault mode, comprising: a circuit transfer function module, a classification table construction module, a clustering module and a calculation identification module;

[0206] The circuit transfer function module is used to determine the circuit transfer function of the corresponding type of grounding fault according to the equivalent circuit model of different types of sheath grounding faults of the high-voltage cable;

[0207] The classification table building module is used to determine the fault characteristic quantities of different types of sheath grounding faults, and calculate the fault characteristic quantity range according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and build a typical fault mode classification table;

[0208] The clustering module is used to establish a K-means clustering model and cluster the fault feature quantities of different types of sheath grounding faults to obtain clustering results of different types of sheath grounding faults;

[0209] The calculation and identification module is used to obtain the detection signal of the target high-voltage cable, calculate the target fault feature quantity of the target high-voltage cable, and determine the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result.

[0210] The cross-connected high-voltage cable sheath grounding fault mode identification system of the present invention establishes equivalent circuit models for typical sheath grounding faults, determines corresponding circuit transfer functions, extracts fault characteristic quantities, constructs a typical fault mode classification table, and performs cluster analysis through a K-means clustering model. In this way, the target high-voltage cable can be identified according to the clustering results to obtain its fault type, thereby greatly improving the diagnostic accuracy of sheath grounding faults and improving the maintenance efficiency of sheath protectors.

[0211] In one or more embodiments of the present invention, the circuit transfer function module is specifically used for:

[0212] The equivalent circuit models of different types of grounding faults are established, and the capacitive current of the sheath loop is calculated according to the sheath current values ​​of the two grounding points of the same sheath loop;

[0213] Among them, the three-phase high-voltage cable is divided into nine sections A1, A2, A3, B1, B2, B3, C1, C2, C3, and current transformers S1, S2, S3, S4, S5, S6 are installed at both ends of the three-phase high-voltage cable respectively;

[0214] The circuit transfer function of the corresponding type of sheath grounding fault calculated according to the capacitive current is specifically:

[0215] 1) Normal grounding of the sheath: The difference in sheath current between the two direct grounding points is the capacitive current. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0216]

[0217] in, is the sheath current value at the current transformer S1; is the sheath current value at the current transformer S4; They are the leakage currents of segments A1, B2, and C3 respectively;

[0218] 2) Low-resistance grounding fault caused by damaged outer sheath: The induced current is divided into two loops. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0219]

[0220] in, is the induced electromotive force on the left side of the fault point in the metal sheath of section A1; is the induced electromotive force on the right side of the fault point in the metal sheath of section A1; They are the induced electromotive force of the metal sheaths of sections B2 and C3 in the A1-B2-C3 loop; are the leakage currents in segments A1, B2, and C3, respectively, and R S is the fault impedance from the fault point to the ground, and R is the ground impedance;

[0221] 3) Sheath protector breakdown fault: The induced current is divided into two loops. The circuit transfer function is constructed according to the current difference detected by current transformer S1 and current transformer S4 as follows:

[0222]

[0223] in, are the induced electromotive force of the metal sheaths of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z L1 is the fault impedance of the fault sheath protector L1 to the ground, and R is the ground impedance;

[0224] 4) Epoxy board breakdown failure: A1-B2-C3 loop and B1-C2-A3 loop are short-circuited. The transfer functions are constructed according to the current difference of A1-B2-C3 loop and B1-C2-A3 loop as follows:

[0225]

[0226]

[0227] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, is the induced electromotive force of the metal sheath of sections B1, C2, and A3 in the B1-C2-A3 loop, are the leakage currents in segments A1, B2, and C3 respectively, R is the ground impedance; R is the ground impedance;

[0228] 5) Water ingress failure in the grounding box: The three circuits are short-circuited, and the circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0229]

[0230] in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z mA1 , Z mB2 , Z mC3 is the impedance of the metal sheath of sections A1, B2, and C3 in the A1-B2-C3 loop, and R is the ground impedance;

[0231] 6) Loose sheath welding point fault: The sheath circuit is open. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0232]

[0233] 7) Ground wire theft fault: The sheath is open to the ground. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows:

[0234]

[0235] 8) Sheath connection error fault: The transfer function is constructed based on the single-point sheath current at the beginning and end of the three loops as follows:

[0236]

[0237]

[0238]

[0239] in, is the sheath current value at the current transformer S1~S6; The induced electromotive force of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively. are the leakage currents of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2, and C3, respectively, mA1 , Z mA2 , Z mA3 , Z mB1 , Z mB2 , Z mB3 , Z mC1 , ZmC2 , Z mC3 They are the impedances of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively.

[0240] The capacitive current of the sheath loop is accurately calculated through the equivalent circuit model, and then the circuit transfer function of the corresponding type of sheath grounding fault can be accurately calculated based on the capacitive current, so that the fault characteristic quantity range can be calculated according to the circuit transfer function to accurately construct a fault mode classification table.

[0241] In one or more embodiments of the present invention, the classification table construction module is specifically used to:

[0242] The vector difference phase angle of sheath current is used as the fault characteristic quantity, and the fault mode of different types of sheath grounding faults is coded;

[0243] Calculating the fault characteristic range corresponding to the type of sheath grounding fault according to the circuit transfer function;

[0244] A typical failure mode classification table is constructed according to the failure mode codes, failure characteristic quantities and failure characteristic quantity ranges.

[0245] By using the vector difference phase angle of the sheath current as the fault characteristic quantity, the fault characteristic quantity range corresponding to the sheath grounding fault type can be directly calculated according to the circuit transfer function, and a typical fault mode classification table can be conveniently constructed in combination with the fault mode coding.

[0246] In one or more embodiments of the present invention, the clustering module is specifically used for:

[0247] Establish a K-means clustering model and generate a random sample set x i As the initial clustering sample, any sample x in the actual sampling is calculated based on the fault mode coding and belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), then the total probability calculation formula is:

[0248]

[0249] Among them, θ k =[θ0,θ1,θ2,θ3,θ4,θ5,θ6,θ7] is a parameter vector, which represents the phase angle of the sheath current phasor difference;

[0250] According to the actual sample phase difference phase angle θ k The initial phase difference angle θ in the fault mode classification table x The ratio of the conditional probability P(x|ω k,θ k ), the calculation formula is:

[0251]

[0252] Taking the variation range of the fault characteristic quantity as the initial reference quantity, the mean vector μ corresponding to normal sheath grounding and different types of sheath grounding faults is set. i As the initial clustering core, 0≤i≤N, N is the total number of samples, calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , and classify it as the cluster where the core of the cluster with the smallest Euclidean distance is located. The calculation formula is:

[0253]

[0254] The Euclidean distance of the probability between the actual sample x and the initial sample is defined as:

[0255]

[0256] Among them, j is the number of samples in the cluster;

[0257] Select the point closest to the average distance of each cluster as the new cluster core, and repeat the above clustering steps until the cluster core and cluster no longer change, and obtain the clustering results of different types of sheath grounding faults;

[0258] By calculating whether any sample x belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), and calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , so as to conduct cluster analysis and obtain the final clustering results.

[0259] In one or more embodiments of the present invention, the calculation and identification module determines the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result in the following specific implementations:

[0260] respectively calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding;

[0261] When the probability density between the target fault feature and one type of sheath grounding fault is the largest, determining the sheath grounding fault type with the largest probability density between the target fault feature as the fault type of the target high-voltage cable;

[0262] When the probability density between the target fault characteristic quantity and the normal grounding of the sheath is the largest, the unprotected grounding fault of the target high-voltage cable is determined.

[0263] By calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding, it can be determined that the maximum probability density corresponds to normal sheath grounding or one of the types of sheath grounding faults, so as to finally realize the identification of the type of sheath grounding fault.

[0264] The present invention provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the steps of the method are implemented.

[0265] The present invention also provides a semi-supervisory identification device for cross-connected high-voltage cable sheath grounding fault mode, comprising the storage medium and a processor, wherein the processor implements the steps of the method when executing the computer program on the storage medium.

[0266] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for identifying a cross-connected high-voltage cable sheath grounding fault mode, characterized in that: The steps include: According to the equivalent circuit model of different types of sheath grounding faults of high-voltage cables, the circuit transfer function of the corresponding type of grounding fault is determined; Determine the fault characteristic quantities of different types of sheath grounding faults, calculate the range of the fault characteristic quantities according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and construct a typical fault mode classification table; A K-means clustering model is established, and the fault characteristic quantities of different types of sheath grounding faults are clustered to obtain the clustering results of different types of sheath grounding faults. Acquire a detection signal of a target high-voltage cable, calculate a target fault feature quantity of the target high-voltage cable, and determine a fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result; The method of determining the circuit transfer function of the corresponding type of grounding fault according to the equivalent circuit model of different types of sheath grounding faults of the high-voltage cable specifically includes: The equivalent circuit models of different types of grounding faults are established, and the capacitive current of the sheath loop is calculated according to the sheath current values ​​of the two grounding points of the same sheath loop; Among them, the three-phase high-voltage cable is divided into nine sections A1, A2, A3, B1, B2, B3, C1, C2, C3, and current transformers S1, S2, S3, S4, S5, S6 are installed at both ends of the three-phase high-voltage cable respectively; The circuit transfer function of the corresponding type of sheath grounding fault calculated according to the capacitive current is specifically: 1) Normal grounding of the sheath: The difference in sheath current between the two direct grounding points is the capacitive current. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: in, is the sheath current value at the current transformer S1; is the sheath current value at current transformer S4; They are the leakage currents of segments A1, B2, and C3 respectively; 2) Low-resistance grounding fault caused by damaged outer sheath: The induced current is divided into two loops. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: in, is the induced electromotive force on the left side of the fault point in the metal sheath of section A1; is the induced electromotive force on the right side of the fault point in the metal sheath of section A1; They are the induced electromotive force of the metal sheaths of sections B2 and C3 in the A1-B2-C3 loop; are the leakage currents in segments A1, B2, and C3, respectively, and R S is the fault impedance from the fault point to the ground, and R is the ground impedance; 3) Sheath protector breakdown fault: The induced current is divided into two loops. The circuit transfer function is constructed according to the current difference detected by current transformer S1 and current transformer S4 as follows: in, are the induced electromotive force of the metal sheaths of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z L1 is the fault impedance of the fault sheath protector L1 to the ground, and R is the ground impedance; 4) Epoxy board breakdown failure: A1-B2-C3 loop and B1-C2-A3 loop are short-circuited. The transfer functions are constructed according to the current difference of A1-B2-C3 loop and B1-C2-A3 loop as follows: in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, is the induced electromotive force of the metal sheath of sections B1, C2, and A3 in the B1-C2-A3 loop, are the leakage currents in segments A1, B2, and C3 respectively, R is the ground impedance; R is the ground impedance; 5) Water ingress failure in the grounding box: The three circuits are short-circuited, and the circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z mA1 , Z mB2 , Z mC3 is the impedance of the metal sheath of sections A1, B2, and C3 in the A1-B2-C3 loop, and R is the ground impedance; 6) Loose sheath welding point fault: The sheath circuit is open. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: 7) Ground wire theft fault: The sheath is open to the ground. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: 8) Sheath connection error fault: The transfer function is constructed based on the single-point sheath current at the beginning and end of the three loops as follows: in, is the sheath current value at the current transformer S1~S6; The induced electromotive force of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively. are the leakage currents of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2, and C3, respectively, mA1 , Z mA2 , Z mA3 , Z mB1 , Z mB2 , Z mB3 , Z mC1 , Z mC2 , Z mC3 They are the impedances of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively; The method of establishing a K-means clustering model and clustering the fault feature quantities of different types of sheath grounding faults to obtain a clustering result including clustering results of different types of sheath grounding faults specifically includes the following steps: Establish a K-means clustering model and generate a random sample set x i As the initial clustering sample, any sample x in the actual sampling is calculated based on the fault mode coding and belongs to the kth type of sheath grounding fault ω k The conditional probability P(xω k ,θ k ), then the total probability calculation formula is: Among them, θ k =[θ0,θ1,θ2,θ3,θ4,θ5,θ6,θ7] is a parameter vector, which represents the phase angle of the sheath current phasor difference; According to the actual sample phase difference phase angle θ k The initial phase difference angle θ in the fault mode classification table x The ratio of the conditional probability P(xω k ,θ k ), the calculation formula is: Taking the variation range of the fault characteristic quantity as the initial reference quantity, the mean vector μ corresponding to normal sheath grounding and different types of sheath grounding faults is set. i As the initial clustering core, 0≤i≤N, N is the total number of samples, calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , and classify it as the cluster where the core of the cluster with the smallest Euclidean distance is located. The calculation formula is: The Euclidean distance of the probability between the actual sample x and the initial sample is defined as: Among them, j is the number of samples in the cluster; The point closest to the average distance of each cluster is selected as the new cluster core, and the above clustering steps are repeated until the cluster core and cluster no longer change, and the clustering results of different types of sheath grounding faults are obtained.

2. The method for identifying a cross-connected high-voltage cable sheath grounding fault mode according to claim 1 is characterized in that: The method of determining the fault characteristic quantities of different types of sheath grounding faults, calculating the range of the fault characteristic quantities according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and constructing a typical fault mode classification table specifically includes the following steps: The vector difference phase angle of sheath current is used as the fault characteristic quantity, and the fault mode encoding is performed for different types of sheath grounding faults. Calculating the fault characteristic range corresponding to the type of sheath grounding fault according to the circuit transfer function; A typical failure mode classification table is constructed according to the failure mode codes, failure characteristic quantities and failure characteristic quantity ranges.

3. The method for identifying a cross-connected high-voltage cable sheath grounding fault mode according to any one of claims 1 to 2, characterized in that: The step of determining the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result specifically includes the following steps: Calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding respectively; When the probability density between the target fault feature and one type of sheath grounding fault is the largest, determining the sheath grounding fault type with the largest probability density between the target fault feature as the fault type of the target high-voltage cable; When the probability density between the target fault characteristic quantity and the normal grounding of the sheath is the largest, the unprotected grounding fault of the target high-voltage cable is determined.

4. A method for identifying a cross-connected high-voltage cable sheath grounding fault mode, characterized in that: include: Circuit transfer function module, classification table building module, clustering module and computational identification module; The circuit transfer function module is used to determine the circuit transfer function of the corresponding type of grounding fault according to the equivalent circuit model of different types of sheath grounding faults of the high-voltage cable; The classification table building module is used to determine the fault characteristic quantities of different types of sheath grounding faults, and calculate the fault characteristic quantity range according to the circuit transfer function and in combination with the detection signal of the sheath grounding fault, and build a typical fault mode classification table; The clustering module is used to establish a K-means clustering model and cluster the fault feature quantities of different types of sheath grounding faults to obtain clustering results of different types of sheath grounding faults; The calculation and identification module is used to obtain a detection signal of a target high-voltage cable, calculate a target fault feature quantity of the target high-voltage cable, and determine a fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result; The circuit transfer function module is specifically used for: The equivalent circuit models of different types of grounding faults are established, and the capacitive current of the sheath loop is calculated according to the sheath current values ​​of the two grounding points of the same sheath loop; Among them, the three-phase high-voltage cable is divided into nine sections A1, A2, A3, B1, B2, B3, C1, C2, C3, and current transformers S1, S2, S3, S4, S5, S6 are installed at both ends of the three-phase high-voltage cable respectively; The circuit transfer function of the corresponding type of sheath grounding fault calculated according to the capacitive current is specifically: 1) Normal grounding of the sheath: The difference in sheath current between the two direct grounding points is the capacitive current. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: in, is the sheath current value at the current transformer S1; is the sheath current value at current transformer S4; They are the leakage currents of segments A1, B2, and C3 respectively; 2) Low-resistance grounding fault caused by damaged outer sheath: The induced current is divided into two loops. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: in, is the induced electromotive force on the left side of the fault point in the metal sheath of section A1; is the induced electromotive force on the right side of the fault point in the metal sheath of section A1; They are the induced electromotive force of the metal sheaths of sections B2 and C3 in the A1-B2-C3 loop; are the leakage currents in segments A1, B2, and C3, respectively, and R S is the fault impedance from the fault point to the ground, and R is the ground impedance; 3) Sheath protector breakdown fault: The induced current is divided into two loops. The circuit transfer function is constructed according to the current difference detected by current transformer S1 and current transformer S4 as follows: in, are the induced electromotive force of the metal sheaths of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z L1 is the fault impedance of the fault sheath protector L1 to the ground, and R is the ground impedance; 4) Epoxy board breakdown failure: A1-B2-C3 loop and B1-C2-A3 loop are short-circuited. The transfer functions are constructed according to the current difference of A1-B2-C3 loop and B1-C2-A3 loop as follows: in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, is the induced electromotive force of the metal sheath of sections B1, C2, and A3 in the B1-C2-A3 loop, are the leakage currents in segments A1, B2, and C3 respectively, R is the ground impedance; R is the ground impedance; 5) Water ingress failure in the grounding box: The three circuits are short-circuited, and the circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: in, is the induced electromotive force of the metal sheath of sections A1, B2 and C3 in the A1-B2-C3 circuit, are the leakage currents in segments A1, B2, and C3, respectively, and Z mA1 , Z mB2 , Z mC3 is the impedance of the metal sheath of sections A1, B2, and C3 in the A1-B2-C3 loop, and R is the ground impedance; 6) Loose sheath welding point fault: The sheath circuit is open. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: 7) Ground wire theft fault: The sheath is open to the ground. The circuit transfer function is constructed based on the current difference detected by current transformer S1 and current transformer S4 as follows: 8) Sheath connection error fault: The transfer function is constructed based on the single-point sheath current at the beginning and end of the three loops as follows: in, is the sheath current value at the current transformer S1~S6; The induced electromotive force of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively. are the leakage currents of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2, and C3, respectively, mA1 , Z mA2 , Z mA3 , Z mB1 , Z mB2 , Z mB3 , Z mC1 , Z mC2 , Z mC3 They are the impedances of the metal sheaths of sections A1, A2, A3, B1, B2, B3, C1, C2 and C3 respectively; The classification table construction module is specifically used for: The vector difference phase angle of sheath current is used as the fault characteristic quantity, and the fault mode encoding is performed for different types of sheath grounding faults. Calculating the fault characteristic range corresponding to the type of sheath grounding fault according to the circuit transfer function; Construct a typical fault mode classification table according to the fault mode codes, fault characteristic quantities and fault characteristic quantity ranges; The clustering module is specifically used for: Establish a k-means clustering model and generate a random sample set x i As the initial clustering sample, any sample x in the actual sampling is calculated based on the fault mode coding and belongs to the kth type of sheath grounding fault ω k The conditional probability P(x|ω k ,θ k ), then the total probability calculation formula is: Among them, θ k =[θ0,θ1,θ2,θ3,θ4,θ5,θ6,θ7] is a parameter vector, which represents the phase angle of the sheath current phasor difference; According to the actual sample phase difference phase angle θ k The initial phase difference angle θ in the fault mode classification table x The ratio of the conditional probability P(x|ω k ,θ k ), the calculation formula is: Taking the variation range of the fault characteristic quantity as the initial reference quantity, the mean vector μ corresponding to normal sheath grounding and different types of sheath grounding faults is set. i As the initial clustering core, 0≤i≤N, N is the total number of samples, calculate the random sample set x i With all mean vectors μ i The Euclidean distance μ between i , and classify it as the cluster where the core of the cluster with the smallest Euclidean distance is located. The calculation formula is: The Euclidean distance of the probability between the actual sample x and the initial sample is defined as: Among them, j is the number of samples in the cluster; Select the point closest to the average distance of each cluster as the new cluster core, and repeat the above clustering steps until the cluster core and cluster no longer change, and obtain the clustering results of different types of sheath grounding faults; The specific implementation of the calculation and identification module determining the fault type of the target high-voltage cable based on the target fault feature quantity and the clustering result is as follows: Calculating the probability density between the target fault characteristic quantity and different types of sheath grounding faults and normal sheath grounding respectively; When the probability density between the target fault feature and one type of sheath grounding fault is the largest, determining the sheath grounding fault type with the largest probability density between the target fault feature as the fault type of the target high-voltage cable; When the probability density between the target fault characteristic quantity and the normal grounding of the sheath is the largest, the unprotected grounding fault of the target high-voltage cable is determined.

5. A computer-readable storage medium storing a computer program, 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 3 are implemented.

6. A semi-supervised identification device for cross-connected high-voltage cable sheath grounding fault mode, characterized in that: The method comprises the storage medium and a processor as described in claim 5, wherein the processor implements the steps of the method as described in any one of claims 1 to 3 when executing the computer program on the storage medium.

Images