A method and device for locating grounding electrode line fault based on modulus network analysis

Abstract

The present invention relates to the field of power system protection and control, and discloses a method and device for locating grounding electrode line faults based on modulus network analysis, including: S1, collecting electrical quantity data of the measuring end of the grounding electrode line; S2, extracting characteristic harmonic components in the electrical quantity data by using S transformation; S3, combining the characteristic harmonic components with the fault equivalent circuit and fault point boundary conditions of the grounding electrode line to establish a fault modulus network of the grounding electrode line; S4, based on the decoupled fault modulus network, calculating the voltage, current and measurement impedance along the grounding electrode line according to the impedance and admittance parameters of the grounding electrode line; S5, establishing a fault location function, and bringing the calculated voltage and current along the line into the fault location function. The method proposed by the present invention can still ensure high ranging accuracy when a long-distance, high-resistance grounding fault occurs in the grounding electrode line.

Description

Technical Field

[0001] The present invention relates to the field of power system protection and control, and in particular to a method and a device for locating a grounding electrode line fault based on modulus network analysis. Background Art

[0002] The UHV DC transmission system is in a bipolar loop operation mode, and the grounding electrode plays the role of circulating the unbalanced current of the system and clamping the neutral point voltage. If a single-pole fault occurs in the bipolar DC transmission system, the normal pole will operate in a single-pole-earth loop mode, and the operating current of the DC system will flow into the earth through the grounding electrode line. In order to avoid the impact of DC bias magnetism on the converter station equipment and the threat of large current entering the ground to the safety of people and animals, the length of some grounding electrode lines has exceeded 100km. The grounding electrode line is operated in parallel with double-circuit lines on the same tower. As the length of the grounding electrode line increases, it is easy to fail when operating under severe weather and geographical conditions.

[0003] The fault location methods for the grounding electrode lines of the currently built and put into operation UHV DC transmission systems are mainly divided into: pulse injection method, fault traveling wave method and fault analysis method. The pulse injection method is affected by its principle and the injection pulse. This method requires the installation of additional signal injection equipment, and the method is prone to failure when a near-end fault or a transient fault occurs in the grounding electrode line. The algorithm based on traveling waves estimates the fault location according to the time it takes for the fault transient traveling wave to propagate along the grounding electrode line. The positioning accuracy of this algorithm depends on the accurate identification of the traveling wave head and the calculation accuracy of the traveling wave velocity. In addition, the UHV DC transmission system is in a bipolar balanced operation mode, and the traveling wave signal in the grounding electrode line is weak and difficult to detect accurately. The ranging algorithm using the fault transient traveling wave will be difficult to apply. The fault analysis method is based on the line parameters of the grounding electrode line and the measured signals at both ends to obtain the distribution law of the voltage and equivalent impedance along the line, and then use the regular characteristics to obtain the location of the fault point. However, this method has a large positioning result error when a long-distance and high-resistance fault occurs in the grounding electrode line. It does not meet the on-site needs.

[0004] Therefore, it is necessary to propose a method for locating grounding electrode line faults with high precision, which is of great significance for quickly troubleshooting and handling grounding electrode line faults and ensuring safe and stable operation of the system. Summary of the invention

[0005] In order to solve the above problems, the present invention aims at different types of grounding faults occurring in the grounding electrode line, establishes a grounding electrode line fault modulus network by combining the grounding electrode line fault equivalent circuit and the fault point boundary conditions, and on this basis uses the 12th harmonic component contained in the unbalanced current of the grounding electrode line to calculate the electrical quantity distribution along the grounding electrode and measure the impedance, and finally provides a grounding electrode line fault locating method and device based on modulus network analysis based on the feature that the imaginary part of the measured impedance is the smallest at the fault point.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for locating a grounding electrode line fault based on modulus network analysis, comprising:

[0008] S1. Collect electrical quantity data at both ends (the beginning and the end) of the grounding electrode line.

[0009] The present invention needs to utilize the voltage and current measurement signals of the grounding electrode line, so current measuring points are installed at the beginning and end of the grounding electrode line to obtain the current recording data of the two grounding lines (the first and second circuits arranged in parallel with each other). and Install a voltage measuring point on the neutral busbar of the grounding electrode to obtain the measured voltage at the head end of the grounding electrode line In order to eliminate the reflection of harmonic components at the end of the grounding line and improve the calculation accuracy of the voltage and current distributed along the line, a matching resistor R is installed at the end of the grounding line. p , whose resistance is equal to the wave impedance of the grounding electrode line. In order to reduce the influence of the matching resistance on the actual operation, an LC parallel band-stop filter with a resonant frequency of 600Hz is installed at both ends of the matching resistance, which serves to provide a path for the DC component.

[0010] S2. Extract characteristic harmonic components from the electrical quantity data using S transformation.

[0011] In view of the good time-frequency characteristics of the S transform, the present invention uses the S transform to extract the head-end voltage in the electrical quantity data collected by the grounding electrode line. The 12th harmonic voltage First terminal current The 12th harmonic current The second terminal current The 12th harmonic current and the second terminal current The 12th harmonic current Of course, other harmonic values ​​can also be set according to actual conditions. Since 12-pulse converters are used on both the rectifier and inverter sides of the UHV DC transmission system, 12k harmonic components (k is a natural number) will be generated on the DC side during AC / DC power conversion. When k=1, the 12th harmonic (600Hz) has the largest content, that is, the 12th harmonic component dominates all harmonic components. From a measurement perspective, it is recommended to use the 12th harmonic, which is conducive to measurement and analysis.

[0012] S3. Combine the characteristic harmonic components with the fault equivalent circuit and fault point boundary conditions of the grounding electrode line to establish a fault modulus network of the grounding electrode line.

[0013] When a single-circuit grounding fault occurs in the grounding electrode line, the boundary conditions of the fault point are: the current of the unfaulted branch is 0, and the voltage at the fault point is the transition resistance R g The product of the current flowing through it;

[0014] When a double-circuit grounding fault occurs in the grounding electrode line, the boundary conditions of the fault point are: the voltages at the fault points of the two lines (the first line and the second line) are equal and equal to the voltage drop on the transition resistance, and the fault current flowing into the earth of the two lines is equal to half of the total current flowing through the fault branch.

[0015] After a ground fault occurs in the grounding line, the second-order Karenberg transformation matrix The characteristic harmonic components of the voltage at the beginning and end of the grounding electrode line and the current at the first end First terminal current The second terminal current and the second terminal current The characteristic harmonic components of the fault modulus network are decoupled;

[0016]

[0017] in, is the characteristic harmonic component of the voltage at the head end of the grounding electrode line, is the characteristic harmonic component of the voltage at the end of the grounding electrode line, is the characteristic harmonic component of the current at the head end of the grounding electrode line, is the characteristic harmonic component of the current at the end of the grounding electrode line, is the characteristic harmonic component of the voltage at the first end of the first circuit. is the characteristic harmonic component of the terminal voltage of the first circuit, is the characteristic harmonic component of the voltage at the first end of the second circuit. is the characteristic harmonic component of the terminal voltage of the second circuit, is the voltage at the first end of the grounding electrode line The zero-mode component of the characteristic harmonic component, is the voltage at the first end of the grounding electrode line The line mode components of the characteristic harmonic components, is the voltage at the end of the grounding line The zero-mode component of the characteristic harmonic component, is the voltage at the end of the grounding line The line mode components of the characteristic harmonic components, is the current at the first end of the grounding electrode line The zero-mode component of the characteristic harmonic component, is the current at the first end of the grounding electrode line The line mode components of the characteristic harmonic components, is the current at the end of the grounding electrode line The zero-mode component of the characteristic harmonic component, is the current at the end of the grounding electrode line The line mode component of the characteristic harmonic component of , x is the harmonic order, where,

[0018] That is to say, subscripts I and II represent two grounding electrode lines respectively; subscripts M and N represent the first and last ends of the grounding electrode line respectively; subscripts 0 and 1 represent the zero mode component and the line mode component respectively.

[0019] Furthermore, the second-order Karen Bell transformation matrix can be used The characteristic harmonic components of the voltage and current at the fault point are decoupled; in the present invention, the fault of the grounding electrode line includes a single-circuit grounding fault and a double-circuit grounding fault.

[0020] When a single-circuit line fails, the decoupling transformation expression at the fault point is:

[0021]

[0022]

[0023] When a double-circuit line fault occurs, the decoupling transformation expression at the fault point is:

[0024]

[0025]

[0026] In formulas (2) and (3), and are the zero-mode voltage and line-mode voltage at the fault point, respectively. and are the zero-mode current and line-mode current at the fault point, respectively. is the characteristic harmonic component of the voltage of the first circuit when a single-circuit line fails. is the characteristic harmonic component of the voltage of the second circuit when a single-circuit line fails, is the characteristic harmonic component of the current of the first circuit when a single-circuit line fails, is the characteristic harmonic component of the current of the second circuit when a single-circuit line fails. is the characteristic harmonic component of the voltage at the fault point when a double-circuit line fails, It is the characteristic harmonic component of the current at the fault point during a double-circuit line fault.

[0027] Finally, a zero-mode component network and a line-mode component network can be established respectively according to the decoupled zero-mode component and line-mode component. The combination of the zero-mode component network and the line-mode component network is collectively referred to as a fault mode network.

[0028] S4, based on the decoupled fault modulus network, calculating the characteristic harmonic components of the voltage, current and measurement impedance along the grounding electrode line according to the impedance and admittance parameters of the grounding electrode line;

[0029] The long-line equation is used to calculate the voltage, current distribution and measurement impedance along the grounding electrode line:

[0030]

[0031] in, is the characteristic harmonic component of the voltage and current at a certain node in the grounding electrode line, and the subscripts h and k represent any two nodes on the grounding electrode line; is the grounding line wave impedance; is the grounding line wave impedance.

[0032] The expression for calculating the measured impedance at the fault point based on the obtained voltage distribution and current distribution along the grounding electrode is:

[0033]

[0034] in, is the calculated characteristic harmonic component of the voltage at the fault point; is the calculated characteristic harmonic component of the current at the fault point.

[0035] S5. Establishing fault location function Get the fault point location;

[0036] in, They represent the characteristic harmonic components of the voltage and current at the fault point at a distance d from the head end of the grounding electrode line. The fault location function is to locate the fault according to the characteristic that the imaginary part of the impedance measured at the fault point is the smallest, that is, to solve G x The distance d corresponding to the minimum value of (d) is the fault point location.

[0037] The present invention also discloses a grounding electrode line fault location system based on modulus network analysis, comprising:

[0038] A collection module, used to collect electrical quantity data at the measuring end of the grounding electrode line;

[0039] An S transformation module, used for extracting characteristic harmonic components in the electrical quantity data by using S transformation;

[0040] A fault modulus network building module, used to combine the fault of the grounding electrode line with the fault equivalent circuit and fault point boundary conditions of the grounding electrode line to establish a fault modulus network of the grounding electrode line;

[0041] A voltage and current calculation module is used to calculate the characteristic harmonic component of the voltage at the fault point of the grounding line based on the decoupled fault modulus network and the impedance and admittance parameters of the grounding line. and characteristic harmonic components of current Respectively represent the characteristic harmonic components of the voltage and current at the fault point d away from the head end of the grounding electrode line;

[0042] Fault location module, used to locate the fault point according to the established fault location function The fault point location is obtained by calculation and positioning.

[0043] As an optimization, the fault location module performs fault location based on the characteristic that the imaginary part of the impedance measured at the fault point is the smallest, that is, solving G x (d) The distance d corresponding to the minimum value is the fault point location.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] 1. The prior art uses a concentrated parameter line model or a distributed parameter line model that does not consider line coupling, and the positioning accuracy is poor when a long-distance, high-resistance grounding fault occurs in the grounding electrode line. The algorithm proposed in the present invention uses a distributed parameter model that considers line coupling, which is not affected by line distributed capacitance and line coupling in principle, and can still ensure high ranging accuracy when a long-distance, high-resistance grounding fault occurs in the grounding electrode line.

[0046] 2. The positioning method of the present invention does not require additional high-frequency signal injection and has good engineering practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0048] Figure 1 This is a simplified schematic diagram of a circuit including a grounding electrode;

[0049] Figure 2 It is the equivalent circuit of single-circuit grounding fault of grounding pole line;

[0050] Figure 3 It is a single-circuit ground fault modulus network of the grounding pole line;

[0051] Figure 4 It is the equivalent circuit of double-circuit grounding fault of grounding pole line;

[0052] Figure 5 It is a double-circuit ground fault modulus network of the grounding pole line;

[0053] Figure 6 Single-circuit line ground fault location results. DETAILED DESCRIPTION

[0054] 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.

[0055] Example 1

[0056] The fault location algorithm proposed in the present invention is based on the modulus network after the grounding electrode line is decoupled, and the 12th harmonic component of the grounding electrode line measurement end is extracted to obtain the voltage distribution and current distribution along the grounding electrode line. Then, the voltage and current of the grounding electrode line fault point can be obtained by phase modulus inverse transformation, and then the measured impedance at the fault point can be obtained. Finally, the fault location is performed according to the characteristic that the imaginary part of the measured impedance at the fault point is the smallest, and the algorithm includes the following steps:

[0057] S1. Collect electrical quantity data at the measuring end of the grounding electrode line.

[0058] like Figure 1 The figure is a simplified schematic diagram of the grounding electrode line of the embodiment of the present invention. The grounding electrode line is a double-circuit line on the same tower (the first circuit I and the second circuit II) running in parallel, and current measuring points are installed at the first and last ends of the grounding electrode line to obtain the current recording data of the two circuits respectively. and (in, is the first end current of the first circuit, is the second head end current at the head end of the second circuit, is the first end current at the end of the first circuit and is the second end current at the end of the second circuit ), the voltage measuring point is installed on the neutral busbar of the grounding pole to obtain the measured voltage at the head end of the line In order to eliminate the reflection of harmonic components at the end of the grounding line and improve the calculation accuracy of the voltage and current distributed along the line, a matching resistor R is installed at the end of the grounding line. p, whose resistance is equal to the wave impedance of the grounding electrode line. In order to reduce the influence of the matching resistance on the actual operation, an LC parallel band-stop filter with a resonant frequency of 600Hz is installed at both ends of the matching resistance, which serves to provide a path for the DC component.

[0059] S2. Extract characteristic harmonic components from the electrical quantity data using S transformation.

[0060] In view of the good time-frequency characteristics of the S transform, taking the 12th harmonic of the electrical quantity data as an example, the present invention uses the S transform to extract the head-end voltage in the electrical quantity data collected by the grounding electrode line The 12th harmonic voltage First terminal current The 12th harmonic current The second terminal current The 12th harmonic current and the second terminal current The 12th harmonic current

[0061] S3. Combine the characteristic harmonic components with the fault equivalent circuit and fault point boundary conditions of the grounding electrode line to establish a fault modulus network of the grounding electrode line.

[0062] The equivalent circuit of a single-circuit grounding fault in the grounding electrode line is as follows: Figure 2 As shown in the figure, assume that the fault occurs in line II (the second circuit), the distance between the fault point and the head end M is d, and the transition resistance is R g , the length of the grounding electrode line is l, and the boundary conditions of the fault point are:

[0063] The equivalent circuit of a double-circuit grounding fault in the grounding electrode line is as follows Figure 4 As shown in the figure, the distance between the fault point and the head end M is d, and the transition resistance is R g , the line length is l, and the boundary conditions of the fault point are: is the characteristic harmonic component of the voltage at the fault point, is the characteristic harmonic component of the total current flowing through the fault point of the two loop lines, is the characteristic harmonic component of the current flowing through the fault point in loop line I, is the characteristic harmonic component of the current flowing through the fault point in loop line II, is the characteristic harmonic component of the voltage at the fault point in loop line I, It is the characteristic harmonic component of the voltage at the fault point in loop line II.

[0064] Using the second-order Karen Bell transformation matrix The characteristic harmonic component of the voltage at the beginning and end of the grounding electrode line (x=12, that is, the characteristic harmonic component takes the 12th harmonic, and the same applies to the following) and the first end current First terminal current The second terminal current and the second terminal current The characteristic harmonic components of are decoupled to obtain the fault modulus network (zero mode component network and line mode component network);

[0065]

[0066] in, is the 12th harmonic value of the voltage at the head end of the grounding electrode line, is the 12th harmonic value of the voltage at the end of the grounding electrode line, is the 12th harmonic value of the current at the head end of the grounding electrode line, is the 12th harmonic value of the current at the end of the grounding electrode line, is the 12th harmonic value of the voltage at the first end of the first circuit, is the 12th harmonic value of the terminal voltage of the first circuit, is the 12th harmonic value of the voltage at the first end of the second circuit. is the 12th harmonic value of the terminal voltage of the second circuit, is the voltage at the first end of the grounding electrode line The zero-mode component of the 12th harmonic value, is the voltage at the first end of the grounding electrode line The line mode component of the 12th harmonic value, is the voltage at the end of the grounding line The zero-mode component of the 12th harmonic value, is the voltage at the end of the grounding line The line mode component of the 12th harmonic value, is the current at the first end of the grounding electrode line The zero-mode component of the 12th harmonic value, is the current at the first end of the grounding electrode line The line mode component of the 12th harmonic value, is the current at the end of the grounding electrode line The zero-mode component of the 12th harmonic value, is the current at the end of the grounding electrode line The line mode component of the 12th harmonic value, where

[0067] That is, subscripts I and II represent two grounding electrode lines respectively; subscripts M and N represent the first and last ends of the grounding electrode line respectively; subscripts 0 and 1 represent the zero mode component and the line mode component respectively.

[0068] Furthermore, the second-order Karenberg transformation matrix can be used Decouple the 12th harmonic values ​​of voltage and current at the fault point;

[0069] When a single-circuit line fails, the decoupling transformation expression at the fault point is:

[0070]

[0071]

[0072] When a double-circuit line fault occurs, the decoupling transformation expression at the fault point is:

[0073]

[0074]

[0075] From equations (1) and (2), it can be seen that when a single-circuit grounding fault occurs in the grounding electrode line, the line mode voltage corresponding to the 12th harmonic value of the head-end voltage is The zero-mode voltage corresponding to the 12th harmonic value of the first-end voltage However, the line mode voltage and zero mode voltage at the fault point are not zero.

[0076] It can be seen from formula (3) that when a double-circuit grounding fault occurs in the grounding electrode line, all the line mode components at the fault point are 0, and only the zero mode component exists.

[0077] Furthermore, a corresponding fault modulus network can be established according to the decoupled zero mode component and line mode component, and the fault modulus network includes a zero mode component network and a line mode component network. Figure 3 As shown, the double-circuit grounding fault modulus network is as follows Figure 5 shown.

[0078] S4, based on the decoupled fault modulus network, calculating the characteristic harmonic components of the voltage, current and measurement impedance along the grounding electrode line according to the impedance and admittance parameters of the grounding electrode line;

[0079] For a single-circuit grounding fault, the zero-mode voltage at the fault point is calculated based on the decoupled fault modulus network. and line mode voltage

[0080]

[0081] in, is the propagation constant of the grounding electrode line corresponding to the zero-mode component network; is the propagation constant of the grounding electrode line corresponding to the line mode component network; is the wave impedance of the grounding electrode line corresponding to the zero-mode component network; is the wave impedance of the grounding electrode line corresponding to the line mode component network; Z0 is the zero mode impedance per unit length of the grounding electrode line; Z1 is the line mode impedance per unit length of the grounding electrode line; Y0 is the zero mode admittance per unit length of the grounding electrode line; Y1 is the line mode admittance per unit length of the grounding electrode line, d is the distance from the fault point to the head end of the grounding electrode line,

[0082] In a line mode component network with a single-circuit ground fault, for the two lines divided by the fault point, the voltages on the M side (head end) and the N side (end) can be listed as follows:

[0083]

[0084] Wherein, x is the distance from the fault point to the N side, that is, x+d=l.

[0085] By solving equation (5), we can get:

[0086]

[0087] in, They are respectively the currents in the grounding electrode lines before and after the fault point in the line mode component network.

[0088] By combining equations (4) and (6), and using phase inverse transformation, we can get the voltage and current at the fault point after a single-circuit grounding fault occurs in the grounding electrode line:

[0089]

[0090] in, is the 12th harmonic value of the fault point voltage, It is the 12th harmonic value of the current at the fault point.

[0091] For a double-circuit grounding fault, the decoupled modulus network only has zero-mode components. Based on this, the voltage and current at the fault point in the zero-mode component network are:

[0092]

[0093]

[0094] Where x represents the distance from the fault point to the end of the grounding electrode line in the zero-mode component network;

[0095] Therefore, by combining equations (8) and (9), the 12th harmonic value of the voltage at the fault point after a double-circuit grounding fault occurs in the grounding electrode line can be obtained by using phase inverse transformation: and current The 12th harmonic value:

[0096]

[0097] in, is the 12th harmonic voltage value at the fault point, It is the 12th harmonic current value at the fault point.

[0098] The voltage at the fault point calculated based on equations (7) (single-circuit fault) and (10) (double-circuit fault) is and fault point current The expression for the measured impedance at the fault point is:

[0099]

[0100] S5. Establishing fault location function (12), get the fault point location;

[0101] in, They represent the 12th harmonic values ​​of the voltage and current at the fault point d away from the head end of the grounding electrode line. The fault location function is to locate the fault according to the characteristic that the imaginary part of the impedance measured at the fault point is the smallest, that is, to solve G 12 (d) The distance d corresponding to the minimum value is the fault point location.

[0102] After a line fault occurs, the 12th harmonic component of the grounding electrode line measurement end is extracted, and the voltage and current distribution of the entire line are calculated based on the grounding electrode line impedance and admittance parameters to solve G 12 (d) The distance d corresponding to the minimum value is the fault point location.

[0103] Example 2

[0104] This embodiment obtains other harmonics of the electrical quantity data, and the remaining steps are the same as those of the first embodiment.

[0105] Example 3

[0106] The present invention also discloses a grounding electrode line fault location system based on modulus network analysis, comprising:

[0107] A collection module, used to collect electrical quantity data at the measuring end of the grounding electrode line;

[0108] An S transformation module, used for extracting characteristic harmonic components in the electrical quantity data by using S transformation;

[0109] A fault modulus network building module, used to combine the fault of the grounding electrode line with the fault equivalent circuit and fault point boundary conditions of the grounding electrode line to establish a fault modulus network of the grounding electrode line;

[0110] A voltage and current calculation module is used to calculate the characteristic harmonic component of the voltage at the fault point of the grounding line based on the decoupled fault modulus network and the impedance and admittance parameters of the grounding line. and characteristic harmonic components of current Respectively represent the characteristic harmonic components of the voltage and current at the fault point d away from the head end of the grounding electrode line;

[0111] Fault location module, used to locate the fault point according to the established fault location function The fault point location is obtained by calculation and positioning.

[0112] In this embodiment, the fault location module performs fault location based on the characteristic that the imaginary part of the impedance measured at the fault point is the smallest, that is, solving G x (d) The distance d corresponding to the minimum value is the fault point location.

[0113] Simulation verification:

[0114] The present invention builds a simulation model of a bipolar UHV DC transmission system with a grounding electrode line based on PSCAD / EMTDC software, and uses MATLAB to verify the accuracy and effectiveness of the proposed fault location method. The rated transmission capacity of the DC system in bipolar operation mode is 8000MW. The unbalanced current flowing through the grounding electrode line is about 45A, and the line length is 101km.

[0115] Based on the simulation model constructed by the present invention, a single-circuit grounding fault occurs on the grounding electrode line l2 at 75 km from the head end through a 200Ω transition resistor. In this paper, the 12th harmonic component of the voltage and current after the fault is extracted by S transform in MATLAB to verify the fault location algorithm. The results are as follows: Figure 6 As shown (more results for double-circuit and single-circuit faults are given in Tables 1 and 2, Figure 6 This is just an example of a single-circuit fault at 75 km. ). It can be seen that the positioning function G x (d) The minimum values ​​are obtained at 75.1 km and 101 km, corresponding to the fault point and the pole point respectively. The absolute error of ranging at this time is 0.1 km.

[0116] To further verify the effectiveness of the algorithm, the grounding fault is set to occur at different fault locations in the grounding electrode line for testing, and the maximum transition resistance considered is 200Ω. The specific simulation results are shown in Tables 1 and 2.

[0117] Table 1 Single-circuit ground fault location results

[0118]

[0119] Table 2 Test results of grounding line disconnection fault

[0120]

[0121] It can be seen from the simulation results that the proposed fault location algorithm can achieve accurate fault location within the entire length of the grounding electrode line, and the ranging error does not exceed 1% of the entire length of the grounding electrode line, which meets the engineering requirements.

[0122] 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 method for locating grounding electrode line faults based on modulus network analysis, characterized in that: include: S1. Collect electrical quantity data at the beginning and end of the grounding electrode line; S2. Extracting characteristic harmonic components in the electrical quantity data by using S transformation; S3, combining the characteristic harmonic component with the fault equivalent circuit and fault point boundary conditions of the grounding electrode line to establish a fault modulus network of the grounding electrode line; S4, based on the fault modulus network, calculating the characteristic harmonic components of the voltage, current and measurement impedance along the grounding electrode line according to the impedance and admittance parameters of the grounding electrode line; For a single-circuit grounding fault, the zero-mode voltage at the fault point is calculated based on the fault modulus network. and line mode voltage : ；（1） in, , is the propagation constant of the grounding electrode line corresponding to the zero-mode component network; is the propagation constant of the grounding electrode line corresponding to the line mode component network; , is the wave impedance of the grounding electrode line corresponding to the zero-mode component network; , is the wave impedance of the grounding electrode line corresponding to the line mode component network; is the zero-mode impedance per unit length of the grounding electrode line; is the line mode impedance per unit length of the grounding electrode line; is the zero mode admittance per unit length of the grounding electrode line; is the line mode admittance per unit length of the grounding electrode line, d is the distance between the fault point and the head end of the grounding electrode line, Indicates the voltage at the beginning of the grounding line The zero-mode component of the 12th harmonic component, is the current at the first end of the grounding electrode line The zero mode component of the 12th harmonic component; Represents the line mode component of the 12th harmonic component of the fault point current; In a line mode component network with a single-circuit ground fault, for the two lines divided by the fault point, the voltages at the beginning and end can be expressed as follows: ；（2） in, x is the distance from the fault point to the end, that is x+d=l , l is the length of the grounding electrode line; By solving equation (2), we can get: ；（3） in, , They are the 12th harmonic components of the current in the grounding electrode line before and after the fault point in the line mode component network; By combining equations (1) and (3), and using phase inverse transformation, we can obtain that after a single-circuit grounding fault occurs in the grounding electrode line, the voltage and current at the fault point are: ；（4） in, is the 12th harmonic component of the voltage at the fault point located in the second loop line, is the 12th harmonic component of the current at the fault point located in the second loop line; Indicates the 12th harmonic component of the fault point voltage, Indicates the 12th harmonic component of the fault point current; For a double-circuit grounding fault, the fault modulus network only has a zero-mode component. Based on this, the voltage and current at the fault point in the zero-mode component network are: ；（5） ；（6） in, x Indicates the distance from the fault point to the end of the grounding electrode line. d is the distance between the fault point and the beginning of the grounding electrode line, that is, x+d=l , l is the length of the grounding electrode line; The zero-mode component of the 12th harmonic component of the fault point voltage is represented by It represents the 12th harmonic component of the current in the grounding electrode line passing through the fault point in the zero-mode component network. , They are the 12th harmonic components of the current in the grounding electrode line before and after the fault point in the zero-mode component network, , is the propagation constant of the grounding electrode line corresponding to the zero-mode component network; , is the wave impedance of the grounding electrode line corresponding to the zero-mode component network; Indicates the voltage at the beginning of the grounding line The zero-mode component of the 12th harmonic component, is the current at the first end of the grounding electrode line The zero mode component of the 12th harmonic component; is the current at the end of the grounding electrode line The zero mode component of the 12th harmonic component; represents transition resistance; Therefore, by combining equations (5) and (6), the 12th harmonic component of the voltage at the fault point of the second circuit line after a double-circuit grounding fault occurs in the grounding electrode line can be obtained by using phase inverse transformation: and the 12th harmonic component of the current : ；（7） in, is the 12th harmonic component of the fault point current, is the 12th harmonic component of the fault point voltage; The fault point voltage calculated based on equations (4) and (7) is and fault point current , the expression of measured impedance at the fault point is: （8）； S5. Establishing fault location function , and bring the calculated voltage and current along the line into the fault location function to obtain the fault point location.

2. A method for locating grounding electrode line faults based on modulus network analysis according to claim 1, characterized in that: The grounding electrode line includes a first circuit and a second circuit connected in parallel with each other, and the electrical quantity data includes a head-end voltage at the head end of the grounding electrode line. , the first head end current of the first circuit head end , the first end current at the end of the first circuit , the second first-end current of the first end of the second circuit and the second end current at the end of the second circuit .

3. A method for locating grounding electrode line faults based on modulus network analysis according to claim 2, characterized in that: In S3, using the Karen Bell transformation matrix S= The characteristic harmonic components of the voltage at the beginning and end of the grounding electrode line and the current at the first end , first terminal current , the second first-end current and the second terminal current The characteristic harmonic components of are decoupled to obtain the fault modulus network, and the calculation formula of the fault modulus network is: ； in, is the characteristic harmonic component of the voltage at the head end of the grounding electrode line, is the characteristic harmonic component of the voltage at the end of the grounding electrode line, is the characteristic harmonic component of the current at the head end of the grounding electrode line, is the characteristic harmonic component of the current at the end of the grounding electrode line, is the characteristic harmonic component of the voltage at the first end of the first circuit. is the characteristic harmonic component of the terminal voltage of the first circuit, is the characteristic harmonic component of the voltage at the first end of the second circuit. is the characteristic harmonic component of the terminal voltage of the second circuit, is the voltage at the first end of the grounding electrode line The zero-mode component of the characteristic harmonic component, is the voltage at the first end of the grounding electrode line The line mode components of the characteristic harmonic components, is the voltage at the end of the grounding line The zero-mode component of the characteristic harmonic component, is the voltage at the end of the grounding line The line mode components of the characteristic harmonic components, is the current at the first end of the grounding electrode line The zero-mode component of the characteristic harmonic component, is the current at the first end of the grounding electrode line The line mode components of the characteristic harmonic components, is the current at the end of the grounding electrode line The zero-mode component of the characteristic harmonic component, is the current at the end of the grounding electrode line The line mode component of the characteristic harmonic component of , x is the harmonic order, where, 。 4. A method for locating grounding electrode line faults based on modulus network analysis according to claim 3, characterized in that: The fault equivalent circuit includes a single-circuit grounding fault equivalent circuit and a double-circuit grounding fault equivalent circuit.

5. The method for locating grounding electrode line fault based on modulus network analysis according to claim 2, characterized in that: When a single-circuit grounding fault occurs in the grounding electrode line, the boundary conditions of the fault point are: the current of the unfaulted branch is 0, and the voltage at the fault point is the transition resistance. R g The product of the current flowing through it; When a double-circuit grounding fault occurs in the grounding electrode line, the boundary conditions of the fault point are: the voltages at the fault points of the first and second circuits are equal and equal to the voltage drop on the transition resistance, and the fault current flowing into the earth of the first and second circuits is equal to half of the total current flowing through the fault branch.

6. A method for locating grounding electrode line faults based on modulus network analysis according to claim 1, characterized in that: In S5, the fault location function is to locate the fault according to the characteristic that the imaginary part of the impedance measured at the fault point is the smallest, that is, to solve The distance d corresponding to the minimum value is the fault point location.

7. A method for locating grounding electrode line faults based on modulus network analysis according to claim 2, characterized in that: The characteristic harmonic components include the first-end voltage The 12th harmonic voltage , the first head end current The 12th harmonic current , the first terminal current The 12th harmonic current , the second first end current The 12th harmonic current and the second terminal current The 12th harmonic current .

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