High-voltage cable defect identification method and system based on cross interconnection grounding ring current

Abstract

The invention discloses a high-voltage cable defect identification method and system based on cross-connected grounding circulating current, and the method comprises the steps: constructing a sheath circulating current equivalent model of a three-phase cable cross-connected grounding system for a single-core cable model in a cross-connected grounding mode, and calculating a sheath circulating current value; based on a field-circuit coupling model of a multi-physical field, metal sheath loss and cable internal temperature of different types of typical defects are obtained, and a typical defect mode classification table of the cross interconnection system is constructed; establishing an integrated learning model based on a LightGBM algorithm, and training the integrated learning model to obtain a trained integrated learning model; and calculating circulation data of the target high-voltage cable, obtaining a target defect characteristic quantity of the target high-voltage cable, and classifying the target high-voltage cable based on the trained integrated learning model to obtain a defect type of the target high-voltage cable. According to the method, the system circulation calculation precision and the high-voltage cable defect identification precision and accuracy are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a method and system for identifying high-voltage cable defects based on cross-connected ground loop currents. Background Art

[0002] High-voltage cross-linked polyethylene (XLPE) cables are widely used in major power transmission projects such as UHV and EHV. Their insulation performance is crucial to the safety and stability of the power system. As the operating life increases, cables are susceptible to various factors and failures, which seriously affect the safe and stable operation of the power grid. Since they are usually laid underground, traditional planned maintenance lacks pertinence, and the diagnosis and treatment of fault defects are difficult. At present, the operating status of the cable is mainly judged by analyzing the sheath circulating current, but most of them only analyze the calculation method of the induced current component in the sheath circulating current, and directly ignore the leakage current component, and do not consider the influence of changes in various parameters of the cross-connected system, resulting in low accuracy, efficiency and accuracy in high-voltage cable defect identification.

[0003] In view of this, this application is hereby filed. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing technology mainly judges the operating status of the cable by analyzing the sheath circulating current, but most of them only analyze the calculation method of the induced current component in the sheath circulating current, and directly ignore the leakage current component, and do not consider the influence of changes in various parameters of the cross-connected system, resulting in low accuracy, efficiency and accuracy in high-voltage cable defect identification. The purpose of the present invention is to provide a high-voltage cable defect identification method and system based on cross-connected grounding loop current, which significantly improves the calculation accuracy of the system circulating current and meets the requirements of circulating current analysis and monitoring of various typical defects. The present invention achieves high-precision high-voltage cable defect identification capability and greatly improves the efficiency and accuracy of defect processing in the cross-connected system of high-voltage cables.

[0005] The present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for identifying high voltage cable defects based on cross-connected ground loop currents, the method comprising:

[0007] According to the single-core cable model of cross-connected grounding, the sheath circulation equivalent model of the three-phase cable cross-connected grounding system is constructed; based on the sheath circulation equivalent model, the sheath circulation value is calculated;

[0008] According to the sheath circulation value, based on the field-circuit coupling model of multi-physics fields, the metal sheath loss and cable internal temperature of different types of typical defects are obtained, and a typical defect mode classification table of the cross-connection system is constructed;

[0009] Establish an integrated learning model based on the LightGBM algorithm, and train the integrated learning model based on the LightGBM algorithm according to the sheath circulation value and the typical defect mode classification table to obtain a trained integrated learning model;

[0010] The circulating current data of the target high-voltage cable is calculated to obtain the target defect characteristic quantity of the target high-voltage cable, and the target high-voltage cable is classified based on the trained ensemble learning model to obtain the defect type of the target high-voltage cable.

[0011] The above technical scheme, considering that the existing technology adopts the circuit method, only analyzes the calculation method of the induced current component in the sheath circulation, and directly ignores the leakage current component; therefore, the present invention solves the problem of ignoring the leakage current component based on the field-circuit coupling idea, solves the field-circuit coupling model of the multi-physical field, and solves the problem of ignoring the leakage current component. Based on the sheath circulation value and the typical defect mode classification table, the present invention considers the influence of the changes in various parameters of the cross-connection system, achieves high-precision high-voltage cable defect identification capability, and greatly improves the efficiency and accuracy of defect handling of the high-voltage cable cross-connection system.

[0012] Furthermore, for the single-core cable model of the cross-connected grounding method, a sheath circulation equivalent model of the three-phase cable cross-connected grounding system is constructed; based on the sheath circulation equivalent model, the sheath circulation value is calculated, including:

[0013] S1.1. Based on the three-phase cross-connected grounding method, each cable part in the single-core cable model is divided into three sections of equal length. Each section is grounded through the sheath protector in the transposition box, and the two terminal metal sheaths of each cross-connected section are directly grounded;

[0014] Among them, the three-phase high-voltage cable is divided into three phases a, b, and c. The a-phase cable is divided into three sections a1, a2, and a3. The b-phase cable is divided into three sections b1, b2, and b3. The c-phase cable is divided into three sections c1, c2, and c3.

[0015] S1.2. According to the equivalent circuit diagram of the single-core cable, the loop current equation for the sheath circulation is obtained. The loop current equation is as follows:

[0016]

[0017] In the formula, They are the induced voltages generated by the currents in the cable core conductors of sections a1, a2, and a3, respectively. is the induced voltage generated by the current in the cable core conductors of sections b1, b2, and b3. The induced voltage generated by the current in the cable core conductors of sections c1, c2 and c3; is the ground circulation, R eqis the equivalent resistance; is the induced voltage on the metal sheath of the i-th section of the land cable of phase a cable generated by the circulating current of the metal sheath of phases b and c, is the induced voltage on the metal sheath of the i-th section of the land cable of phase b cable generated by the circulating current of the metal sheath of phases a and c, is the induced voltage on the metal sheath of the i-th section of the land cable of phase c generated by the circulating current of the metal sheaths of phases a and b; is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; Z ai is the self-impedance of the metal sheath of the i-th section of the a-phase cable, Z bi is the self-impedance of the metal sheath of the i-th section of the b-phase cable, Z ci is the self-impedance of the metal sheath of the i-th section of the c-phase cable.

[0018] Among them, the self-impedance Z of the metal sheath of the i-th section of the a-phase cable, b-phase cable, and c-phase cable is ai , Z bi , Z ci The specific expression is:

[0019]

[0020] In the formula, R ai is the sheath resistance of the i-th section of the a-phase cable, R bi is the sheath resistance of the i-th section of the b-phase cable, R ci is the sheath resistance of the i-th section of the c-phase cable; L aai is the self-inductance per unit length of the loop formed by the metal sheath of the i-th section of the a-phase cable and the ground, L bbi is the self-inductance per unit length of the loop formed by the metal sheath of the i-th section of the b-phase cable and the ground, L cci is the self-inductance per unit length of the loop formed by the metal sheath of the i-th section of the c-phase cable and the ground; l i is the length of the i-th cable line.

[0021] Among them, the induced voltage generated by the current in the core conductor of the i-th section of the three-phase cable a, b, c is The specific expression is:

[0022]

[0023] Where M Ab is the unit mutual inductance between the a-phase cable core and the b-phase cable sheath, M Ac is the unit mutual inductance between the a-phase cable core and the c-phase cable sheath; M Ba is the unit mutual inductance between the b-phase cable core and the a-phase cable sheath, M Bcare the unit mutual inductances between the b-phase cable core and the c-phase cable sheath; M Ca is the unit mutual inductance between the c-phase cable core and the a-phase cable sheath, M Cb are the unit mutual inductances between the c-phase cable core and the b-phase cable sheath; M Aa is the unit mutual inductance between the a-phase cable core and the a-phase cable sheath, M Bb is the unit mutual inductance between the b-phase cable core and the b-phase cable sheath, M Cc is the unit mutual inductance between the c-phase cable core and the c-phase cable sheath; is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase C cable.

[0024] Among them, the induced voltage on the metal sheath of the i-th section of the land cable of the three-phase cable a, b, c is generated by the circulating current of the metal sheath of the other two phases. The calculation formula is

[0025]

[0026] Where M abi is the mutual inductance per unit length of the loop formed by the sheath of the i-th segment of the a-phase and b-phase cables and the ground, M aci is the mutual inductance per unit length of the loop formed by the sheath of the i-th section of the a-phase and c-phase cables and the ground, M bci is the mutual inductance per unit length of the loop formed by the sheath of the i-th section of the b-phase and c-phase cables and the ground; is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; l i is the length of the i-th cable line.

[0027] S1.3. Substitute formula (2) to formula (4) into the loop equation group of formula (1) to derive the grounding circulation matrix equation, and use the grounding circulation matrix equation as the sheath circulation equivalent model; based on the sheath circulation equivalent model, calculate the sheath circulation value.

[0028] The expression of the equivalent model of sheath circulation is:

[0029]

[0030] In the formula, is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; They are the induced voltages generated by the currents in the cable core conductors of sections a1, a2, and a3, respectively. is the induced voltage generated by the current in the cable core conductors of sections b1, b2, and b3. is the induced voltage generated by the current in the cable core conductors of sections c1, c2, and c3; Z 11 To Z 33 is impedance;

[0031] Where, the impedance Z 11 To Z 33 The calculation formula is:

[0032]

[0033] Furthermore, according to the sheath circulation value, based on the field-circuit coupling model of multi-physics fields, the metal sheath loss and internal temperature of the cable due to different types of typical defects are obtained, including:

[0034] Establish a finite element calculation model for the single-core cable model, and perform mesh division on the finite element calculation model;

[0035] The sheath circulation value is input into the finite element calculation model as an excitation source to obtain the internal conductor conductivity and electromagnetic loss distribution results of the cable; the internal temperature field distribution of the cable is calculated based on the electromagnetic loss distribution results;

[0036] The temperature field distribution inside the cable is input into the finite element calculation model, and the electromagnetic loss distribution is recalculated; and the electromagnetic loss distribution results before and after are compared. If the calculation error of the comparison exceeds the set error range, the iteration is repeated until the set error range is met and the metal sheath loss and the internal temperature of the cable are output.

[0037] In the above technical scheme, the present invention combines the bidirectional coupling idea of ​​the field path, firstly inputs the sheath circulation value as the excitation source into the finite element calculation model, obtains the cable internal conductor conductivity and electromagnetic loss distribution results; calculates the cable internal temperature field distribution according to the electromagnetic loss distribution results; then inputs the cable internal temperature field distribution into the finite element calculation model, recalculates the electromagnetic loss distribution; and compares the electromagnetic loss distribution results before and after, until the calculation error of the comparison meets the set error range, thereby obtaining the metal sheath loss and the cable internal temperature. The present invention overcomes the original path method that directly ignores the influence of the leakage current component.

[0038] Furthermore, a typical defect mode classification table of the cross-connection system is constructed, including:

[0039] Taking the metal sheath loss and the internal temperature of the cable as defect characteristic quantities, the typical defects of different types of cross-connection systems are coded to obtain the defect type coding;

[0040] According to the defect characteristic quantity and defect type coding, a typical defect mode classification table of the cross-connection system is constructed.

[0041] Furthermore, according to the sheath circulation value and the typical defect mode classification table, the integrated learning model based on the LightGBM algorithm is trained to obtain the trained integrated learning model, including:

[0042] According to the typical defect pattern classification table, a sample set for defect classification training and testing is constructed;

[0043] Standardize the defect feature quantities in the sample set, and divide the sample set into a training set and a validation set according to a preset ratio;

[0044] Set the hyperparameter range of the integrated learning model based on the LightGBM algorithm, use the fuzzy entropy algorithm to pre-train the integrated learning model based on the LightGBM algorithm, and use data augmentation technology to simulate different cable detection environments and conditions to find the optimal hyperparameter combination;

[0045] The optimal hyperparameter combination is used as the final model parameters, and the training set is reused to train the ensemble learning model based on the LightGBM algorithm to obtain a trained ensemble learning model.

[0046] Furthermore, it also includes:

[0047] Based on the validation set, the trained ensemble learning model is verified to obtain a verified ensemble learning model.

[0048] Furthermore, the target high-voltage cable is classified based on the trained ensemble learning model, including:

[0049] Judge whether the target high-voltage cable is operating normally: if the cable status is predicted to be normal by the input defect feature quantity, there is no response; if the cable status is predicted to be abnormal by the input defect feature quantity, the trained ensemble learning model is used to classify the target high-voltage cable to obtain a specific defect category recognition result.

[0050] In a second aspect, the present invention further provides a high voltage cable defect identification system based on cross-connected ground loop current, the system comprising:

[0051] The circulating current calculation unit is used to construct a sheath circulating current equivalent model of a three-phase cable cross-connected grounding system for a single-core cable model of a cross-connected grounding method; based on the sheath circulating current equivalent model, the sheath circulating current value is calculated;

[0052] The field-circuit coupling unit is used to obtain the metal sheath loss and cable internal temperature of different types of typical defects according to the sheath circulation value and the field-circuit coupling model based on multi-physics fields, and to build a typical defect mode classification table for the cross-connection system;

[0053] The model building and training unit is used to establish an integrated learning model based on the LightGBM algorithm, and train the integrated learning model based on the LightGBM algorithm according to the sheath circulation value and the typical defect mode classification table to obtain a trained integrated learning model;

[0054] The defect type identification unit is used to calculate the circulating current data of the target high-voltage cable, obtain the target defect characteristic quantity of the target high-voltage cable, and classify the target high-voltage cable based on the trained integrated learning model to obtain the defect type of the target high-voltage cable.

[0055] Furthermore, the field-circuit coupling unit includes:

[0056] The finite element model building subunit is used to build a finite element calculation model for a single-core cable model and to perform meshing on the finite element calculation model;

[0057] The bidirectional coupling subunit is used to input the sheath circulating current value as an excitation source into the finite element calculation model to obtain the distribution results of the internal conductor conductivity and electromagnetic loss of the cable; calculate the internal temperature field distribution of the cable according to the electromagnetic loss distribution results; input the internal temperature field distribution of the cable into the finite element calculation model to recalculate the electromagnetic loss distribution;

[0058] The comparison subunit is used to compare the electromagnetic loss distribution results of the two times before and after. If the calculation error of the comparison exceeds the set error range, it will be iterated again until the set error range is met and the metal sheath loss and the internal temperature of the cable are output.

[0059] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0060] 1. The present invention provides a high-voltage cable defect identification method and system based on cross-connected grounding loop currents. The present invention is based on the field-circuit coupling concept, solves the field-circuit coupling model of multi-physical fields, and solves the problem of ignoring leakage current components; the present invention is based on the sheath circulating current values ​​and the typical defect mode classification table, and takes into account the influence of changes in various parameters of the cross-connected system. The method significantly improves the calculation accuracy of the system circulating current and meets the requirements of circulating current analysis and monitoring of various typical defects; it achieves high-precision high-voltage cable defect identification capabilities and greatly improves the efficiency and accuracy of defect processing in the high-voltage cable cross-connected system.

[0061] 2. The present invention provides a method for calculating the ground loop current loss of cross-connection of high-voltage cables based on the field-circuit coupling concept, which has the characteristics of high precision, simple operation, good reliability, etc. By performing parameter setting operations in the field-circuit coupling model, there is no need for repeated modeling and input, and more complex analysis and judgment can be performed.

[0062] 3. The present invention constructs a typical defect recognition model based on the LightGBM algorithm (i.e., an integrated learning model based on the LightGBM algorithm) for detecting the operating status of cross-connected grounded high-voltage cables. The LightGBM algorithm shows better classification and recognition effects in this field, and can efficiently analyze multi-dimensional feature data; it has distributed support and has great advantages in processing multi-classification problems of large-capacity data samples.

[0063] 4. The technical method of the present invention fills the technical gap in the industry at home and abroad: At present, the typical defect identification methods for cross-connected grounded high-voltage cables are mostly focused on online monitoring to judge the operating status of the cable, and the online monitoring system mainly includes online temperature monitoring, online partial discharge monitoring and online sheath circulation monitoring. However, the current online monitoring methods are mostly limited to over-limit threshold judgment and local defect identification, which limits its ability to accurately determine the defect location and quickly identify the defect type. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0065] Figure 1 It is a flow chart of a high voltage cable defect identification method based on cross-connected ground loop current of the present invention;

[0066] Figure 2 It is a schematic diagram of the sheath circulating current equivalent model of the three-phase cable cross-interconnected grounding system of the present invention;

[0067] Figure 3 The present invention is a structural block diagram of a high-voltage cable defect identification system based on cross-connected ground loop currents. DETAILED DESCRIPTION

[0068] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0069] The existing technology mainly judges the operation status of the cable by analyzing the sheath circulation, but most of them only analyze the calculation method of the induced current component in the sheath circulation, and directly ignore the leakage current component, and do not consider the influence of the changes in various parameters of the cross-connection system, resulting in low accuracy, low efficiency and accuracy in the identification of high-voltage cable defects. Therefore, the present invention designs a high-voltage cable defect identification method and system based on the cross-connection grounding circulation. The present invention is based on the field-circuit coupling concept, solves the field-circuit coupling model of the multi-physical field, and solves the problem of ignoring the leakage current component; based on the sheath circulation value and the typical defect mode classification table, the present invention considers the influence of the changes in various parameters of the cross-connection system, achieves high-precision high-voltage cable defect identification capability, and greatly improves the efficiency and accuracy of defect processing in the cross-connection system of high-voltage cables.

[0070] Example 1

[0071] like Figure 1 As shown, the present invention provides a method for identifying high voltage cable defects based on cross-connected ground loop currents, the method comprising:

[0072] S1. For the single-core cable model of the cross-connected grounding method, a sheath circulation equivalent model of the three-phase cable cross-connected grounding system is constructed; based on the sheath circulation equivalent model, the sheath circulation value is calculated;

[0073] S2. According to the sheath circulation value, based on the field-circuit coupling model of multi-physics fields, the metal sheath loss and cable internal temperature of different types of typical defects are obtained, and a typical defect mode classification table of the cross-connection system is constructed;

[0074] S3. Establish an integrated learning model based on the LightGBM algorithm, and train the integrated learning model based on the LightGBM algorithm according to the sheath circulation value and the typical defect mode classification table to obtain a trained integrated learning model;

[0075] S4. Calculate the circulating current data of the target high-voltage cable, obtain the target defect characteristic quantity of the target high-voltage cable, and classify the target high-voltage cable based on the trained integrated learning model to obtain the defect type of the target high-voltage cable.

[0076] The above technical scheme, considering that the existing technology adopts the circuit method, only analyzes the calculation method of the induced current component in the sheath circulation, and directly ignores the leakage current component; therefore, the present invention solves the problem of ignoring the leakage current component based on the field-circuit coupling idea, solves the field-circuit coupling model of the multi-physical field, and solves the problem of ignoring the leakage current component. Based on the sheath circulation value and the typical defect mode classification table, the present invention considers the influence of the changes in various parameters of the cross-connection system, achieves high-precision high-voltage cable defect identification capability, and greatly improves the efficiency and accuracy of defect handling of the high-voltage cable cross-connection system.

[0077] In this embodiment, step S1 specifically includes:

[0078] S1.1. Based on the three-phase cross-interconnection grounding method, each large section (i.e., cable section) in the single-core cable model is divided into three sections of equal length. Each section is grounded through the sheath protector in the transposition box, and the two terminal metal sheaths of each group of cross-interconnection sections are directly grounded;

[0079] Among them, the three-phase high-voltage cable is divided into three phases a, b, and c. The a-phase cable is divided into three sections a1, a2, and a3. The b-phase cable is divided into three sections b1, b2, and b3. The c-phase cable is divided into three sections c1, c2, and c3.

[0080] S1.2. According to the equivalent circuit diagram of the single-core cable, the loop current equation for the sheath circulation is obtained. The loop current equation is as follows:

[0081]

[0082] In the formula, They are the induced voltages generated by the currents in the cable core conductors of sections a1, a2, and a3, respectively. is the induced voltage generated by the current in the cable core conductors of sections b1, b2, and b3. The induced voltage generated by the current in the cable core conductors of sections c1, c2 and c3; is the ground circulation, R eq is the equivalent resistance; is the induced voltage on the metal sheath of the i-th section of the land cable of phase a cable generated by the circulating current of the metal sheath of phases b and c, is the induced voltage on the metal sheath of the i-th section of the land cable of phase b cable generated by the circulating current of the metal sheath of phases a and c, is the induced voltage on the metal sheath of the i-th section of the land cable of phase c generated by the circulating current of the metal sheaths of phases a and b; is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; Z ai is the self-impedance of the metal sheath of the i-th section of the a-phase cable, Z bi is the self-impedance of the metal sheath of the i-th section of the b-phase cable, Z ci is the self-impedance of the metal sheath of the i-th section of the c-phase cable.

[0083] Among them, the self-impedance Z of the metal sheath of the i-th section of the a-phase cable, b-phase cable, and c-phase cable is ai , Z bi , Z ci The specific expression is:

[0084]

[0085] In the formula, R ai is the sheath resistance of the i-th section of the a-phase cable, R bi is the sheath resistance of the i-th section of the b-phase cable, R ci is the sheath resistance of the i-th section of the c-phase cable; L aai is the self-inductance per unit length of the loop formed by the metal sheath of the i-th section of the a-phase cable and the ground, L bbi is the self-inductance per unit length of the loop formed by the metal sheath of the i-th section of the b-phase cable and the ground, L cci is the self-inductance per unit length of the loop formed by the metal sheath of the i-th section of the c-phase cable and the ground; l i is the length of the i-th cable line.

[0086] Among them, the induced voltage generated by the current in the core conductor of the i-th section of the three-phase cable a, b, c is The specific expression is:

[0087]

[0088] Where M Ab is the unit mutual inductance between the a-phase cable core and the b-phase cable sheath, M Ac is the unit mutual inductance between the a-phase cable core and the c-phase cable sheath; M Ba is the unit mutual inductance between the b-phase cable core and the a-phase cable sheath, M Bc are the unit mutual inductances between the b-phase cable core and the c-phase cable sheath; M Ca is the unit mutual inductance between the c-phase cable core and the a-phase cable sheath, M Cb are the unit mutual inductances between the c-phase cable core and the b-phase cable sheath; M Aa is the unit mutual inductance between the a-phase cable core and the a-phase cable sheath, M Bb is the unit mutual inductance between the b-phase cable core and the b-phase cable sheath, M Cc is the unit mutual inductance between the c-phase cable core and the c-phase cable sheath; is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase C cable.

[0089] Among them, the induced voltage on the metal sheath of the i-th section of the land cable of the three-phase cable a, b, c is generated by the circulating current of the metal sheath of the other two phases. The calculation formula is

[0090]

[0091] Where M abiis the mutual inductance per unit length of the loop formed by the sheath of the i-th segment of the a-phase and b-phase cables and the ground, M aci is the mutual inductance per unit length of the loop formed by the sheath of the i-th section of the a-phase and c-phase cables and the ground, M bci is the mutual inductance per unit length of the loop formed by the sheath of the i-th section of the b-phase and c-phase cables and the ground; is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; l i is the length of the i-th cable line.

[0092] S1.3. Substitute formula (2) to formula (4) into the loop equation group of formula (1) to derive the grounding circulation matrix equation, and use the grounding circulation matrix equation as the sheath circulation equivalent model; based on the sheath circulation equivalent model, calculate the sheath circulation value.

[0093] The expression of the equivalent model of sheath circulation is:

[0094]

[0095] In the formula, is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; They are the induced voltages generated by the currents in the cable core conductors of sections a1, a2, and a3, respectively. is the induced voltage generated by the current in the cable core conductors of sections b1, b2, and b3. is the induced voltage generated by the current in the cable core conductors of sections c1, c2, and c3; Z 11 To Z 33 is impedance;

[0096] Where, the impedance Z 11 To Z 33 The calculation formula is:

[0097]

[0098] like Figure 2 As shown, Figure 2 It is a sheath circulating current equivalent model of a three-phase cable cross-interconnected grounding system. Figure 2 middle, is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; is the ground circulation, R eq is the equivalent resistance value, represents the induced voltage generated by the current in the core conductor of the i-th section, represents the induced voltage on the metal sheath of the i-th section of the land cable caused by the circulating current of the other two phases of the metal sheath; Z ai , Z bi , Z ci They represent the self-impedance of the i-th section metal sheath of phase a cable, phase b cable, and phase c cable respectively.

[0099] In this embodiment, step S2 specifically includes:

[0100] S2.1. Establish a finite element calculation model for the single-core cable model and perform mesh division on the finite element calculation model;

[0101] S2.2. Input the sheath circulation value as an excitation source into the finite element calculation model to obtain the internal conductor conductivity and electromagnetic loss distribution results of the cable; calculate the internal temperature field distribution of the cable based on the electromagnetic loss distribution results;

[0102] S2.3. Input the temperature field distribution inside the cable into the finite element calculation model, and recalculate the electromagnetic loss distribution; and compare the electromagnetic loss distribution results before and after. If the calculation error of the comparison exceeds the set error range, iterate again until the set error range is met and the metal sheath loss and the internal temperature of the cable are output;

[0103] S2.4. Taking the metal sheath loss and the internal temperature of the cable as defect characteristic quantities, the typical defects of different types of cross-connection systems are encoded to obtain defect type codes; according to the defect characteristic quantities and defect type codes, a typical defect mode classification table of the cross-connection system is constructed, as shown in Table 1:

[0104] Table 1 Typical defect mode classification table

[0105]

[0106] In the above technical scheme, the present invention combines the bidirectional coupling idea of ​​the field path, firstly inputs the sheath circulation value as the excitation source into the finite element calculation model, obtains the cable internal conductor conductivity and electromagnetic loss distribution results; calculates the cable internal temperature field distribution according to the electromagnetic loss distribution results; then inputs the cable internal temperature field distribution into the finite element calculation model, recalculates the electromagnetic loss distribution; and compares the electromagnetic loss distribution results before and after, until the calculation error of the comparison meets the set error range, thereby obtaining the metal sheath loss and the cable internal temperature. The present invention overcomes the original path method that directly ignores the influence of the leakage current component.

[0107] In this embodiment, in step S3, the integrated learning model based on the LightGBM algorithm is trained according to the sheath circulation value and the typical defect mode classification table to obtain a trained integrated learning model, which specifically includes:

[0108] S3.1. Based on the typical defect pattern classification table, the defect feature quantities and their corresponding defect category codes are used as the sample set for defect classification training and testing; in order to reduce the impact of data differences on the diagnosis effect, the defect feature quantities in the sample set are standardized, and the sample set is divided into a training set and a validation set according to a preset ratio;

[0109] S3.2. Set the hyperparameter range of the integrated learning model based on the LightGBM algorithm, use the fuzzy entropy algorithm to pre-train the integrated learning model based on the LightGBM algorithm, and use data augmentation technology to simulate different cable detection environments and conditions to find the optimal hyperparameter combination;

[0110] S3.3. Use the optimal hyperparameter combination as the final model parameters, reuse the training set to train the ensemble learning model based on the LightGBM algorithm, and obtain a trained ensemble learning model;

[0111] S3.4. Based on the validation set, the trained ensemble learning model is verified to obtain a verified ensemble learning model, thereby verifying the accuracy of the model.

[0112] In this embodiment, the target high-voltage cable is classified based on the trained integrated learning model, including:

[0113] Judge whether the target high-voltage cable is operating normally: if the cable status is predicted to be normal by the input defect feature quantity, there is no response; if the cable status is predicted to be abnormal by the input defect feature quantity, the trained ensemble learning model is used to classify the target high-voltage cable to obtain a specific defect category recognition result.

[0114] In this embodiment, in step S4, the circulating current data of the target high-voltage cable may be calculated using a method similar to that in step S1.

[0115] The method of the present invention significantly improves the calculation accuracy of the system circulation and meets the requirements of circulation analysis and monitoring of various typical defects; the present invention achieves high-precision high-voltage cable defect identification capability and also greatly improves the efficiency and accuracy of defect processing in the high-voltage cable cross-connection system.

[0116] Example 2

[0117] like Figure 3As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides a high-voltage cable defect identification system based on a cross-connected ground loop current, the system uses the high-voltage cable defect identification method based on a cross-connected ground loop current of embodiment 1, and the system corresponds to the high-voltage cable defect identification method based on a cross-connected ground loop current of embodiment 1 in one-to-one function; the system includes:

[0118] The circulating current calculation unit is used to construct a sheath circulating current equivalent model of a three-phase cable cross-connected grounding system for a single-core cable model of a cross-connected grounding method; based on the sheath circulating current equivalent model, the sheath circulating current value is calculated;

[0119] The field-circuit coupling unit is used to obtain the metal sheath loss and cable internal temperature of different types of typical defects according to the sheath circulation value and the field-circuit coupling model based on multi-physics fields, and to build a typical defect mode classification table for the cross-connection system;

[0120] The model building and training unit is used to establish an integrated learning model based on the LightGBM algorithm, and train the integrated learning model based on the LightGBM algorithm according to the sheath circulation value and the typical defect mode classification table to obtain a trained integrated learning model;

[0121] The defect type identification unit is used to calculate the circulating current data of the target high-voltage cable, obtain the target defect characteristic quantity of the target high-voltage cable, and classify the target high-voltage cable based on the trained integrated learning model to obtain the defect type of the target high-voltage cable.

[0122] As a further implementation, the field-circuit coupling unit includes:

[0123] The finite element model building subunit is used to build a finite element calculation model for a single-core cable model and to perform meshing on the finite element calculation model;

[0124] The bidirectional coupling subunit is used to input the sheath circulating current value as an excitation source into the finite element calculation model to obtain the distribution results of the internal conductor conductivity and electromagnetic loss of the cable; calculate the internal temperature field distribution of the cable according to the electromagnetic loss distribution results; input the internal temperature field distribution of the cable into the finite element calculation model to recalculate the electromagnetic loss distribution;

[0125] The comparison subunit is used to compare the electromagnetic loss distribution results of the two times before and after. If the calculation error of the comparison exceeds the set error range, it will be iterated again until the set error range is met and the metal sheath loss and the internal temperature of the cable are output.

[0126] Among them, the execution process of each unit can be executed according to the process steps of the high-voltage cable defect identification method based on cross-connected ground loop current in Example 1, and will not be repeated one by one in this embodiment.

[0127] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0128] 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.

[0129] 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 including 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.

[0130] 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.

[0131] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high voltage cable defect identification method based on cross-connected ground loop current, characterized in that: The method includes: For the single-core cable model of the cross-connected grounding method, a sheath circulation equivalent model of the three-phase cable cross-connected grounding system is constructed; based on the sheath circulation equivalent model, the sheath circulation value is calculated; According to the sheath circulation value, based on the field-circuit coupling model of multi-physics fields, the metal sheath loss and the internal temperature of the cable of different types of typical defects are obtained, and a typical defect mode classification table of the cross-connection system is constructed; Establishing an integrated learning model based on the LightGBM algorithm, and training the integrated learning model based on the LightGBM algorithm according to the sheath circulation value and the typical defect mode classification table to obtain a trained integrated learning model; The circulating current data of the target high-voltage cable is calculated to obtain the target defect characteristic quantity of the target high-voltage cable, and the target high-voltage cable is classified based on the trained integrated learning model to obtain the defect type of the target high-voltage cable.

2. The high voltage cable defect identification method based on cross-connected ground loop current according to claim 1 is characterized in that: According to the single-core cable model of cross-connected grounding, the sheath circulation equivalent model of the three-phase cable cross-connected grounding system is constructed; Based on the sheath circulation equivalent model, the sheath circulation value is calculated, including: Based on the three-phase cross-interconnection grounding method, each cable part in the single-core cable model is divided into three sections of equal length. Each section is grounded through the sheath protector in the transposition box, and the two terminal metal sheaths of each cross-interconnection section are directly grounded. According to the equivalent circuit diagram of the single-core cable, the loop current equation about the sheath circulating current is obtained; Substitute the self-impedance of the i-th section of the metal sheath, the induced voltage and the induced voltage formed by the metal sheath circulating current of the remaining two phases into the loop current equation, derive the grounding circulation current matrix equation, and use the grounding circulation current matrix equation as the sheath circulating current equivalent model; Based on the sheath circulation equivalent model, the sheath circulation value is calculated.

3. The high voltage cable defect identification method based on cross-connected ground loop current according to claim 2 is characterized in that: The expression of the sheath circulation equivalent model is: In the formula, is the ground loop current of phase a cable, is the ground loop current of phase b cable, is the ground loop current of phase c cable; They are the induced voltages generated by the currents in the cable core conductors of sections a1, a2, and a3, respectively. is the induced voltage generated by the current in the cable core conductors of sections b1, b2, and b3. is the induced voltage generated by the current in the cable core conductors of sections c1, c2, and c3; Z 11 To Z 33 For impedance.

4. The high voltage cable defect identification method based on cross-connected ground loop current according to claim 1 is characterized in that: According to the sheath circulation value, based on the field-circuit coupling model of multi-physics fields, the metal sheath loss and cable internal temperature of different types of typical defects are obtained, including: Establishing a finite element calculation model for the single-core cable model, and performing meshing on the finite element calculation model; Input the sheath circulation value as an excitation source into the finite element calculation model to obtain the internal conductor conductivity and electromagnetic loss distribution results of the cable; calculate the internal temperature field distribution of the cable according to the electromagnetic loss distribution results; The temperature field distribution inside the cable is input into the finite element calculation model, and the electromagnetic loss distribution is recalculated; and the electromagnetic loss distribution results before and after are compared. If the calculation error of the comparison exceeds the set error range, the iteration is repeated until the set error range is met and the metal sheath loss and the internal temperature of the cable are output.

5. The high voltage cable defect identification method based on cross-connected ground loop current according to claim 1 or 4, characterized in that: Construct a taxonomy of typical defect modes for cross-connect systems, including: Taking the metal sheath loss and the internal temperature of the cable as defect characteristic quantities, the typical defects of different types of cross-connection systems are coded to obtain the defect type coding; According to the defect characteristic quantity and the defect type code, a typical defect mode classification table of the cross-connection system is constructed.

6. The high voltage cable defect identification method based on cross-connected ground loop current according to claim 1 is characterized in that: According to the sheath circulation value and the typical defect mode classification table, the integrated learning model based on the LightGBM algorithm is trained to obtain a trained integrated learning model, including: According to the typical defect mode classification table, a sample set for defect classification training and testing is constructed; Standardizing the defect feature quantities in the sample set, and dividing the sample set into a training set and a validation set according to a preset ratio; Setting the hyperparameter range of the integrated learning model based on the LightGBM algorithm, pre-training the integrated learning model based on the LightGBM algorithm using the fuzzy entropy algorithm, and using data augmentation technology to simulate different cable detection environments and conditions to find the optimal hyperparameter combination; The optimal hyperparameter combination is used as the final model parameters, and the training set is reused to train the integrated learning model based on the LightGBM algorithm to obtain a trained integrated learning model.

7. The high voltage cable defect identification method based on cross-connected ground loop current according to claim 4 is characterized in that: Also includes: Based on the validation set, the trained ensemble learning model is validated to obtain a validated ensemble learning model.

8. The high voltage cable defect identification method based on cross-connected ground loop current according to claim 1 is characterized in that: Classifying the target high-voltage cable based on the trained integrated learning model includes: It is judged whether the target high-voltage cable is operating normally: if the cable status is predicted to be normal by the input defect feature quantity, there is no response; if the cable status is predicted to be abnormal by the input defect feature quantity, the trained ensemble learning model is used to classify the target high-voltage cable to obtain a specific defect category recognition result.

9. A high voltage cable defect identification system based on cross-connected ground loop current, characterized in that: The system includes: A circulating current calculation unit is used to construct a sheath circulating current equivalent model of a three-phase cable cross-connected grounding system for a single-core cable model of a cross-connected grounding mode; and calculate a sheath circulating current value based on the sheath circulating current equivalent model; A field-circuit coupling unit is used to obtain the metal sheath loss and the internal temperature of the cable of different types of typical defects according to the sheath circulating current value and based on the field-circuit coupling model of multi-physical fields, and to construct a typical defect mode classification table of the cross-connection system; A model building and training unit, used for establishing an integrated learning model based on the LightGBM algorithm, and training the integrated learning model based on the LightGBM algorithm according to the sheath circulation value and the typical defect mode classification table to obtain a trained integrated learning model; The defect type identification unit is used to calculate the circulating current data of the target high-voltage cable, obtain the target defect characteristic quantity of the target high-voltage cable, and classify the target high-voltage cable based on the trained integrated learning model to obtain the defect type of the target high-voltage cable.

10. The high voltage cable defect identification system based on cross-connected ground loop current according to claim 9 is characterized in that: The field-circuit coupling unit comprises: A finite element model building subunit is used to build a finite element calculation model for the single-core cable model and to perform meshing on the finite element calculation model; A bidirectional coupling subunit is used to input the sheath circulating current value as an excitation source into the finite element calculation model to obtain the conductivity of the cable internal conductor and the electromagnetic loss distribution results; calculate the temperature field distribution inside the cable according to the electromagnetic loss distribution results; input the temperature field distribution inside the cable into the finite element calculation model to recalculate the electromagnetic loss distribution; The comparison subunit is used to compare the electromagnetic loss distribution results of the two times before and after. If the calculation error of the comparison exceeds the set error range, it will be iterated again until the set error range is met and the metal sheath loss and the internal temperature of the cable are output.

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