A method and system for measuring a tower grounding resistance

Abstract

The application belongs to the technical field of power grid power supply, and particularly relates to a measurement method and system for tower grounding resistance, which comprises the following steps: constructing a chain linear network model, setting an engineering typical value of the grounding impedance of each tower, constructing a prior admittance matrix, inverting the prior admittance matrix to obtain a prior impedance matrix, injecting a mixed excitation current signal with multiple different frequencies into the grounding lead of the measured tower, synchronously collecting the measured voltage of all nodes, separating the measured voltage under each frequency, calculating an admittance deviation matrix and an impedance deviation matrix, establishing an approximate linear relationship between the impedance deviation matrix and the admittance deviation matrix and a voltage difference vector, solving the approximate linear relationship, obtaining the impedance deviation of the grounding impedance under each frequency relative to the engineering typical value of the grounding impedance, calculating the actual grounding impedance, and separating the actual grounding impedance to obtain the grounding resistance. The application realizes the inversion of the grounding resistance from the external port measurement value without disassembling any grounding lead.

Description

Technical Field

[0001] This application belongs to the field of power grid supply technology, specifically a method and system for measuring the grounding resistance of power poles and towers. Background Technology

[0002] Power transmission towers are the main carriers of power transmission lines, which are a crucial means of current transmission in the entire power grid system. The towers not only provide mechanical support and grounding protection for the lines, but their grounding protection devices and the towers themselves also provide a channel for current to escape. With the development of the power industry and the expanding coverage of power grids, the requirements for the grounding performance of power transmission towers are becoming increasingly stringent.

[0003] The grounding resistance of a pole grounding device is one of its main parameters. Grounding resistance generally refers to the ratio of the potential at the grounding point of an electrical device to the current after a current is injected into it. This resistance changes with the surrounding environment and the duration of the current flow. Its value can be used to determine whether a grounding device or system meets the standards of the regulations and whether it possesses a certain level of safety and effectiveness. If the grounding resistance is too high, when a system fault occurs or a lightning strike occurs, the potential at the grounding point of the electrical equipment will not only directly threaten the safety of all personnel operating the equipment but will also cause more serious traffic and electrical accidents.

[0004] Currently, the main methods for measuring the grounding resistance of power poles are the three-electrode method and the clamp meter method. Since different power poles are interconnected by ground wires, and typically four grounding leads are connected to the power pole, it is usually necessary to disconnect all grounding leads during measurement to obtain a more accurate grounding resistance value. This significantly reduces the efficiency of measurement projects in practical work. Therefore, how to quickly measure the grounding resistance of power poles without disconnecting the grounding leads has become an important problem that needs to be solved. Summary of the Invention

[0005] This application provides a method for measuring the grounding resistance of a tower, which solves the problem of low work efficiency caused by the need to disassemble four grounding leads to measure the grounding resistance.

[0006] This application provides a method for measuring the grounding resistance of a tower, the method comprising: Construct a chain-like linear network model consisting of N towers and their connecting ground wires, where the grounding lead connection point of each tower is defined as a node, and the nodes are connected through ground wire impedance. Set the typical engineering value of the grounding impedance of each tower, and construct the a priori admittance matrix based on the typical engineering value of the grounding impedance. Invert the a priori admittance matrix to obtain the a priori impedance matrix. Multiple mixed excitation current signals of different frequencies are injected into the grounding lead of the tower under test. The measured voltage of all nodes is collected synchronously using a synchronous vector measurement device. The measured voltage at each frequency is separated by phase-locked amplification technology. The difference between the true admittance matrix and the prior admittance matrix is ​​calculated to obtain the admittance bias matrix; The difference between the true impedance matrix and the prior impedance matrix is ​​calculated to obtain the impedance deviation matrix; An approximate linear relationship is established between the impedance deviation matrix, the admittance deviation matrix, and the voltage difference vector based on the Woodbury matrix identity. The voltage difference vector is the difference between the measured voltage and the prior calculated voltage, and the prior calculated voltage is the product of the prior impedance matrix and the injected excitation current signal. Solve for the approximate linear relationship to obtain the impedance deviation of the grounding impedance relative to the typical engineering value of the grounding impedance at each frequency; calculate the actual grounding impedance based on the impedance deviation of the typical engineering value of the grounding impedance, and separate the actual grounding impedance to obtain the grounding resistance.

[0007] Furthermore, the chain-like linear network model satisfies the following node voltage phasor equations: First node: The sum of the ground current of the first node and the current flowing through the first node to the second node equals the current injected into the first node; Intermediate node: Node The ground current, through the first branch road from the first Node flow to the first The current through the node, branch road from the first Node flow to the first The sum of the currents at the nodes equals the current injected into the first node. Node current; End node: node The current to ground and the current through the first branch road from the first Node to Node -1 current equals the injection of the first The current at the node.

[0008] Furthermore, the true admittance matrix corresponding to the chain linear network model is decomposed into the sum of the ground network admittance matrix and the ground admittance diagonal matrix; where the diagonal elements of the ground admittance diagonal matrix are the ground admittances of each tower, the non-zero elements of the ground network admittance matrix only appear between adjacent nodes, the diagonal elements are the sum of the admittances of adjacent branches, and the off-diagonal adjacent elements are the negative branch admittances.

[0009] Furthermore, typical engineering values ​​for the grounding impedance of each tower are defined, and a priori admittance matrix is ​​constructed based on these typical engineering values, including: Select typical engineering values ​​of the grounding impedance of each tower and determine them using the average value method for the entire line, the statistical typical value method, or the segmented assignment method; The true grounding impedance is expressed as the sum of the typical engineering value of the grounding impedance and the deviation, and then converted into the form of grounding admittance. Construct the a priori ground admittance, wherein the elements of the a priori ground admittance are the reciprocals of the typical engineering values ​​of each ground impedance; Substituting the a priori ground admittance into the decomposition of the node admittance matrix yields the a priori admittance matrix, which is equal to the sum of the ground network admittance matrix and the diagonal matrix with the a priori ground admittance as its diagonal element.

[0010] Furthermore, the approximate linear relationship can be expressed as: , in, This represents a typical engineering value for grounding impedance. For the prior voltage, The admittance bias matrix, This is a voltage difference vector. This represents the deviation between the actual grounding impedance and the typical engineering value of the grounding impedance. This is the actual grounding impedance. This represents the typical value of average grounding impedance in engineering projects. This is the impedance deviation matrix; A first-order Taylor expansion of the grounding admittance form at the typical engineering value of the grounding impedance yields a linearized relationship between the admittance deviation and the impedance deviation, i.e., the admittance deviation is approximately equal to the negative impedance deviation divided by the square of the typical engineering value of the grounding impedance. Based on the linearization relationship between admittance bias and impedance bias, the linearization relationship between the admittance bias matrix and the impedance bias matrix is ​​as follows: = .

[0011] Furthermore, the actual grounding impedance is separated to obtain the grounding resistance, including: taking the real part of the grounding impedance as the grounding resistance, dividing the imaginary part of the grounding impedance by the angular frequency to obtain the grounding inductance, taking the average value of the calculation results at multiple frequencies, or using the least squares method to fit the data at multiple frequencies to obtain the optimal estimates of the grounding resistance and grounding inductance.

[0012] Furthermore, the real part of the grounding impedance is taken as the grounding resistance, and the imaginary part of the grounding impedance is divided by the angular frequency and taken as the grounding inductance, expressed as: ,in For frequency node grounding impedance, For nodes grounding resistance, For nodes The grounding inductance, It is the imaginary unit.

[0013] A second aspect of this application provides a system for measuring the grounding resistance of a tower, comprising: The network model construction module is used to construct a chain-like linear network model consisting of N towers and their connecting ground wires, where the grounding lead connection point of each tower is defined as a node, and the nodes are connected through ground wire impedance. The prior parameter setting module is used to set the typical engineering value of the grounding impedance of each tower, and to construct the prior admittance matrix based on the typical engineering value of the grounding impedance. The prior impedance matrix is ​​obtained by inverting the prior admittance matrix. The hybrid excitation injection and measurement module is used to inject multiple hybrid excitation current signals of different frequencies into the grounding lead of the tower under test. The synchronous vector measurement device is used to synchronously collect the measured voltage of all nodes, and the phase-locked amplification technology is used to separate the measured voltage at each frequency. The admittance bias calculation module is used to calculate the difference between the true admittance matrix and the prior admittance matrix to obtain the admittance bias matrix. The impedance deviation calculation module is used to calculate the difference between the actual impedance matrix and the prior impedance matrix to obtain the impedance deviation matrix. The linear relationship approximation module is used to establish an approximate linear relationship between the impedance deviation matrix, the admittance deviation matrix, and the voltage difference vector based on the Woodbury matrix identity. The voltage difference vector is the difference between the measured voltage and the prior calculated voltage, and the prior calculated voltage is the product of the prior impedance matrix and the injected excitation current signal. The impedance deviation calculation module is used to solve the approximate linear relationship and obtain the impedance deviation of the grounding impedance relative to the typical engineering value of the grounding impedance at each frequency; the grounding resistance extraction module is used to calculate the actual grounding impedance based on the impedance deviation of the typical engineering value of the grounding impedance and separate the actual grounding impedance to obtain the grounding resistance.

[0014] Compared with the prior art, the advantages of this application are as follows: The method of this application enables the direct inversion of grounding resistance from external port measurements without removing any grounding leads, avoiding the cumbersome operation and safety risks of removing leads in traditional methods; By establishing a chain-like linear network model with the ground wire impedance as a known network parameter, and solving it by decomposing and linearizing the node admittance matrix, the grounding impedance of each tower can be accurately separated, effectively eliminating the measurement error caused by the parallel ground wire loop in the traditional method. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a chain-like linear network model provided in an embodiment of this application; Figure 2 This is a flowchart illustrating a method for measuring the grounding resistance of a tower, as provided in an embodiment of this application. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0017] For a power transmission system consisting of multiple towers, its internal impedance mainly includes: the grounding resistance of the towers themselves, the resistance and inductance of the towers themselves, and the resistance and inductance of the connecting wires. Compared with the magnitude of the grounding resistance, the resistance of the towers themselves and the resistance of the connecting wires are negligible, and the inductive effect of the towers themselves is also very weak. Therefore, in the embodiments of this application, the resistance of the towers themselves and the resistance of the connecting wires are ignored, and the combined effect of the grounding resistance of the towers and the inductance of the connecting wires is mainly considered.

[0018] At the measurement frequency, the ground wire and grounding device are both linear lumped parameter elements, without nonlinearity or dispersion abrupt change; the tower grounding impedance is the node-to-ground complex impedance, which includes grounding resistance, grounding inductance and soil frequency variation effect; The N-base towers form a chain-like linear network (see [link]). Figure 1 As shown, node Indicates pole tower The grounding lead connection point, the nodes are connected through the ground impedance Connection, number Node voltage is defined as Inject the first The current at a node is defined as , No. Node grounding impedance is defined as .

[0019] based on Figure 1 The established chain-like linear network model consisting of N base towers is shown in [reference]. Figure 2 The present application provides a method for measuring the grounding resistance of a tower, the method comprising: S101, Construct a chain-like linear network model consisting of N base towers and their connecting ground wires (see...). Figure 1 The grounding lead connection point of each tower is defined as a node, and the nodes are connected through ground impedance. Based on Kirchhoff's current law, the node voltage phasor equations of the chain topology are established. The chain linear network model satisfies the following node voltage phasor equations: First node: The sum of the ground current of the first node and the current flowing through the first node to the second node equals the current injected into the first node; expressed as: ,in, This represents the node voltage of the first node. The grounding impedance of the first node is... This represents the node voltage of the second node. The ground impedance of the first branch; For the current injected into the first node. Intermediate nodes: nodes The ground current, through the first branch road from the first Node flow to the first The current through the node, branch road from the first Node flow to the first The sum of the currents at the nodes equals the current injected into the first node. The current at the node is represented as: ,in, For the first Node voltage, For the first Node voltage, branch road ground impedance, branch road ground impedance, For the injection of the first The current at the node, For the first The grounding impedance of the node.

[0020] End node: node The current to ground and the current through the first branch road from the first Node to Node -1 current equals the injection of the first The current at the node.

[0021] The formula is expressed as: ,in, For the first Node voltage, For the first The grounding impedance of the node, branch road ground impedance, For the first Node voltage, For the injection of the first The current at the node.

[0022] The true admittance matrix corresponding to the chain linear network model is decomposed into the sum of the ground network admittance matrix and the ground admittance diagonal matrix; where the diagonal elements of the ground admittance diagonal matrix are the ground admittances of each tower, the non-zero elements of the ground network admittance matrix only appear between adjacent nodes, the diagonal elements are the sum of the admittances of adjacent branches, and the off-diagonal adjacent elements are the negative branch admittances.

[0023] The true admittance matrix is ​​represented as: , For node voltage, Inject current into the node.

[0024] For an N×N true admittance matrix It can be decomposed into the ground network admittance matrix. Diagonal matrix of ground admittance sum: , For the ground network admittance matrix to lie on the matrix diagonal: , in, These are the diagonal elements of the ground network admittance matrix. Represents a node The set of adjacent nodes, Represents a node The ground impedance between node j and node j.

[0025] Off-diagonal lines of the grounding network admittance matrix, when towers are adjacent: , in, These are the off-diagonal elements of the ground network admittance matrix.

[0026] When they are not adjacent, the value is 0.

[0027] Then for the true admittance matrix Its diagonal admittance element: , in, These are the diagonal elements of the true admittance matrix. This represents the actual grounding impedance.

[0028] Define the true grounding impedance matrix Z as: Therefore: ; During the measurement process, an excitation current is first injected into the i-th tower. By simultaneously measuring the voltage of all nodes, the following can be found in the branch under test: ,in Indicates the actual grounding impedance. This represents the voltage at the i-th node.

[0029] However, obtaining only one column does not allow for direct solutions for all towers.

[0030] S102, Set the typical engineering values ​​of the grounding impedance for each tower, and construct a priori admittance matrix based on the typical engineering values ​​of the grounding impedance. Invert the priori admittance matrix to obtain the priori impedance matrix; including: Typical engineering values ​​for the grounding impedance of each tower are selected, determined using the full-line average method, the statistical typical value method, or the segmented assignment method. The typical engineering value for grounding impedance refers to the range of standard resistance values ​​specified for grounding devices in design and acceptance codes for power systems, building lightning protection, and communication engineering projects, to ensure safety and normal equipment operation. The full-line average method assigns a uniform, single value to the grounding impedance of all towers along the entire line. The statistical typical value method assigns different typical impedance values ​​to towers based on statistical patterns from a large amount of measured data. The segmented assignment method divides the entire line into several sections based on terrain, soil conditions, and tower type, using a uniform standard value within each section.

[0031] The actual grounding impedance is expressed as the sum of the typical engineering value and the deviation of the grounding impedance, and then converted into the form of grounding admittance. Based on the typical engineering value of the grounding impedance, the average grounding impedance value of the entire line can be obtained. Assuming the typical engineering value of the average grounding impedance is... The deviation between the actual grounding impedance and the typical engineering value of the grounding impedance is set as follows: Then we have: , in, For the true grounding impedance, the corresponding true grounding admittance is: , in, For nodes True ground admittance, For nodes The prior grounding admittance, This is the deviation between the actual ground admittance and the a priori ground admittance.

[0032] For the above formula Perform a first-order Taylor expansion at this point: , Construct the a priori ground admittance, where the elements of the a priori ground admittance are the reciprocals of the typical engineering values ​​of each ground impedance; expressed as: Substituting these values ​​into the admittance matrix decomposition formula, we obtain the prior admittance matrix for the typical engineering case as follows: , in, Let be the prior admittance matrix. The admittance matrix of the ground network. For prior ground admittance. Typical engineering impedance matrix. Represented as: , The a priori admittance matrix is ​​equal to the sum of the ground network admittance matrix and the diagonal matrix with the a priori ground admittance as its diagonal element.

[0033] S103 injects multiple mixed excitation current signals of different frequencies into the grounding lead of the tower under test, uses a synchronous vector measurement device to synchronously collect the measured voltage of all nodes, and uses lock-in amplification technology to separate the measured voltage at each frequency. S104, calculate the difference between the true admittance matrix and the prior admittance matrix to obtain the admittance bias matrix; expressed as: , in, The admittance bias matrix, The true admittance matrix, Let be the prior admittance matrix.

[0034] S105, calculate the difference between the true impedance matrix and the prior impedance matrix to obtain the impedance deviation matrix; expressed as: , S106, establish an approximate linear relationship between the impedance deviation matrix, the admittance deviation matrix, and the voltage difference vector based on the Woodbury matrix identity. The voltage difference vector is the difference between the measured voltage and the prior calculated voltage, and the prior calculated voltage is the product of the prior impedance matrix and the injected excitation current signal. The process of establishing an approximate linear relationship between the impedance deviation matrix, the admittance deviation matrix, and the voltage difference vector using the Woodbury matrix identity is expressed as follows: , in, This represents a typical engineering value for grounding impedance. For the prior voltage, The admittance bias matrix, This is a vector of voltage differences; A first-order Taylor expansion of the grounding admittance form at the typical engineering value yields a linearized relationship between admittance deviation and impedance deviation, i.e., the admittance deviation is approximately equal to the negative impedance deviation divided by the square of the typical engineering value. Based on the linearization relationship between admittance bias and impedance bias, the linearization relationship between the admittance bias matrix and the impedance bias matrix is ​​as follows: = , This is the impedance deviation matrix.

[0035] S107, solve for the approximate linear relationship to obtain the impedance deviation of the grounding impedance relative to the typical engineering value of the grounding impedance at each frequency; S108, Calculate the actual grounding impedance based on the impedance deviation of the typical engineering value of the grounding impedance, and separate the actual grounding impedance to obtain the grounding resistance. Separating the actual grounding impedance to obtain the grounding resistance includes: taking the real part of the grounding impedance as the grounding resistance, dividing the imaginary part of the grounding impedance by the angular frequency to obtain the grounding inductance, taking the average of the calculation results at multiple frequencies, or using the least squares method to fit the data at multiple frequencies to obtain the optimal estimates of the grounding resistance and grounding inductance.

[0036] For a given frequency, after completing the linearized approximation of the grounding impedance, the complex form of the grounding impedance at that frequency has been obtained. This complex number contains two parts: a real part and an imaginary part. The real part reflects the portion of active power consumed in the grounding path, whose main physical source is the grounding resistance. Therefore, this real part can be directly taken as the estimated value of the grounding resistance at that frequency. The imaginary part reflects the portion of magnetic field energy stored in the grounding path, whose main physical source is the inductive reactance generated by the grounding inductance. The magnitude of the inductive reactance is equal to the angular frequency multiplied by the inductance value. Therefore, in order to deduce the inductance value from the imaginary part, it is necessary to divide the imaginary part by the angular frequency corresponding to the current frequency. The angular frequency is equal to two times pi multiplied by the frequency. The result obtained in this way is the estimated value of the grounding inductance at that frequency. Taking the real part of the grounding impedance as the grounding resistance and dividing the imaginary part of the grounding impedance by the angular frequency as the grounding inductance, it can be expressed as: ,in For frequency node grounding impedance, For nodes grounding resistance, For nodes The grounding inductance, It is the imaginary unit.

[0037] Through the above steps, each frequency corresponds to an observed value for grounding resistance and an observed value for grounding inductance. In actual measurement or identification processes, multiple different frequencies are usually selected, such as the power frequency and its harmonics, or multiple frequency points evenly distributed within a certain range. Each frequency point can independently obtain a grounding resistance value and a grounding inductance value by following the above process.

[0038] Due to random measurement errors, external interference, or minor deviations caused by model linearization approximations, the grounding resistance values ​​obtained at different frequencies will fluctuate slightly. Similarly, the grounding inductance values ​​may also differ. To obtain a more stable and reliable estimate, the arithmetic mean of the grounding resistance values ​​at all frequencies can be taken as the final grounding resistance value. Likewise, the arithmetic mean of the grounding inductance values ​​at all frequencies can be taken as the final grounding inductance value.

[0039] The advantages of the averaging method are its simplicity in calculation, ease of implementation, and ability to offset the effects of random errors to some extent. Its disadvantage is that it cannot identify and eliminate frequency-related trends or systematic biases.

[0040] A more accurate and scientific method than the averaging method is to use the least squares method to fit data at multiple frequencies. This method not only provides optimal estimates of grounding resistance and grounding inductance, but also fully utilizes the linear relationship between frequency and reactance to suppress measurement noise.

[0041] In least squares fitting, the relationship between the real part of the grounding impedance and frequency is treated as a constant function, meaning the resistance does not change with frequency. The real part observations at all frequency points are used as samples to fit a horizontal straight line; the ordinate of this line represents the optimal estimate of the grounding resistance. In practice, this is equivalent to taking a weighted average of the real parts at each frequency, but the least squares method can conveniently handle situations where the confidence level differs at different frequencies.

[0042] For estimating the grounding inductance, the inductance observation value obtained by dividing the imaginary part by the angular frequency is used. Since the grounding inductance is ideally a constant independent of frequency, the inductance observation values ​​calculated at each frequency can also be fitted to a constant, which is the optimal estimate of the grounding inductance.

[0043] On the other hand, embodiments of this application provide a system for measuring the grounding resistance of a tower, comprising: The network model construction module is used to construct a chain-like linear network model consisting of N towers and their connecting ground wires, where the grounding lead connection point of each tower is defined as a node, and the nodes are connected through ground wire impedance. The prior parameter setting module is used to set the typical engineering value of the grounding impedance of each tower, and to construct the prior admittance matrix based on the typical engineering value of the grounding impedance. The prior impedance matrix is ​​obtained by inverting the prior admittance matrix. The hybrid excitation injection and measurement module is used to inject multiple hybrid excitation current signals of different frequencies into the grounding lead of the tower under test. The synchronous vector measurement device is used to synchronously collect the measured voltage of all nodes, and the phase-locked amplification technology is used to separate the measured voltage at each frequency. The admittance bias calculation module is used to calculate the difference between the true admittance matrix and the prior admittance matrix to obtain the admittance bias matrix. The impedance deviation calculation module is used to calculate the difference between the actual impedance matrix and the prior impedance matrix to obtain the impedance deviation matrix. The linear relationship approximation module is used to establish an approximate linear relationship between the impedance deviation matrix, the admittance deviation matrix, and the voltage difference vector based on the Woodbury matrix identity. The voltage difference vector is the difference between the measured voltage and the prior calculated voltage, and the prior calculated voltage is the product of the prior impedance matrix and the injected excitation current signal. The impedance deviation calculation module is used to solve for an approximate linear relationship and obtain the impedance deviation of the grounding impedance relative to the typical engineering value of the grounding impedance at each frequency; the grounding resistance extraction module is used to calculate the actual grounding impedance based on the impedance deviation of the typical engineering value of the grounding impedance and separate the actual grounding impedance to obtain the grounding resistance.

[0044] The following is a specific example: Set up a system with three towers. Assume the ground wire resistance is 0.5Ω, and the actual grounding resistances of towers 1-3 are 8Ω, 13Ω, and 9Ω respectively. The typical engineering value is set to 10Ω. Set the excitation current amplitude to 1A and input the excitation current to tower 2. Build the equivalent model of the three towers in Sinmulink simulation.

[0045] The ground network admittance matrix can be obtained as follows: , The prior admittance matrix is: , The true admittance matrix obtained from the test: , Based on the above voltage values ​​and typical current values ​​in engineering projects, the voltage difference vector is calculated as follows: , , This is the measured voltage.

[0046] After rearranging the Woodbury matrix identity, we get: , get: , , , Using the formula: , Find: , , , Solving for: , , .

[0047] In the above simulation, inductance is ignored, so the obtained grounding impedance is the grounding resistance, which is 8Ω, 13Ω and 9Ω respectively, compared with the actual grounding resistance. It can be seen that the three obtained grounding resistances are close to the actual grounding resistance.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for measuring the grounding resistance of a tower, characterized in that, The method includes: Construct a chain-like linear network model consisting of N towers and their connecting ground wires, where the grounding lead connection point of each tower is defined as a node, and the nodes are connected through ground wire impedance. Set the typical engineering values ​​of the grounding impedance of each tower, and construct the a priori admittance matrix based on the typical engineering values ​​of the grounding impedance. Invert the a priori admittance matrix to obtain the a priori impedance matrix. This includes: selecting the typical engineering values ​​of the grounding impedance of each tower and determining them using the full-line average method, the statistical typical value method, or the segmented assignment method. The true grounding impedance is expressed as the sum of the typical engineering value of the grounding impedance and the deviation, and then converted into the form of grounding admittance. Construct the a priori ground admittance, wherein the elements of the a priori ground admittance are the reciprocals of the typical engineering values ​​of each ground impedance; Substituting the a priori ground admittance into the decomposition of the node admittance matrix yields the a priori admittance matrix, which is equal to the sum of the ground network admittance matrix and the diagonal matrix with the a priori ground admittance as its diagonal element. Multiple mixed excitation current signals of different frequencies are injected into the grounding lead of the tower under test. The measured voltage of all nodes is collected synchronously using a synchronous vector measurement device. The measured voltage at each frequency is separated by phase-locked amplification technology. The difference between the true admittance matrix and the prior admittance matrix is ​​calculated to obtain the admittance bias matrix; The difference between the true impedance matrix and the prior impedance matrix is ​​calculated to obtain the impedance deviation matrix; An approximate linear relationship is established between the impedance deviation matrix, the admittance deviation matrix, and the voltage difference vector based on the Woodbury matrix identity. The voltage difference vector represents the difference between the measured voltage and the prior calculated voltage, where the prior calculated voltage is the product of the prior impedance matrix and the injected excitation current signal. The approximate linear relationship is expressed as: ， in, This represents a typical engineering value for grounding impedance. For the prior voltage, The admittance bias matrix, This is a voltage difference vector. This represents the deviation between the actual grounding impedance and the typical engineering value of the grounding impedance. This is the actual grounding impedance. This represents the typical value of average grounding impedance in engineering projects. This is the impedance deviation matrix; A first-order Taylor expansion of the grounding admittance form at the typical engineering value of the grounding impedance yields a linearized relationship between the admittance deviation and the impedance deviation, i.e., the admittance deviation is approximately equal to the negative impedance deviation divided by the square of the typical engineering value of the grounding impedance. Based on the linearization relationship between admittance bias and impedance bias, the linearization relationship between the admittance bias matrix and the impedance bias matrix is ​​as follows: = ; Solve for the approximate linear relationship to obtain the impedance deviation of the grounding impedance relative to the typical engineering value of the grounding impedance at each frequency; calculate the actual grounding impedance based on the impedance deviation of the typical engineering value of the grounding impedance, and separate the actual grounding impedance to obtain the grounding resistance.

2. The method for measuring the grounding resistance of a tower according to claim 1, characterized in that, The chain-linear network model satisfies the following node voltage phasor equations: First node: The sum of the ground current of the first node and the current flowing through the first node to the second node equals the current injected into the first node; Intermediate node: Node The ground current, through the first branch road from the first Node flow to the first The current through the node, branch road from the first Node flow to the first The sum of the currents at the nodes equals the current injected into the first node. Node current; End node: node The current to ground and the current through the first branch road from the first Node to Node -1 current equals the injection of the first The current at the node.

3. The method for measuring the grounding resistance of a tower according to claim 1, characterized in that, The true admittance matrix corresponding to the chain linear network model is decomposed into the sum of the ground network admittance matrix and the ground admittance diagonal matrix; where the diagonal elements of the ground admittance diagonal matrix are the ground admittances of each tower, the non-zero elements of the ground network admittance matrix only appear between adjacent nodes, the diagonal elements are the sum of the admittances of adjacent branches, and the off-diagonal adjacent elements are the negative branch admittances.

4. The method for measuring the grounding resistance of a tower according to claim 1, characterized in that, Separating the actual grounding impedance to obtain the grounding resistance includes: taking the real part of the grounding impedance as the grounding resistance, dividing the imaginary part of the grounding impedance by the angular frequency to obtain the grounding inductance, taking the average value of the calculation results at multiple frequencies, or using the least squares method to fit the data at multiple frequencies to obtain the optimal estimates of the grounding resistance and grounding inductance.

5. The method for measuring the grounding resistance of a tower according to claim 4, characterized in that, Taking the real part of the grounding impedance as the grounding resistance and dividing the imaginary part of the grounding impedance by the angular frequency as the grounding inductance, it can be expressed as: ,in For frequency node grounding impedance, For nodes grounding resistance, For nodes The grounding inductance, It is the imaginary unit.

6. A system for measuring the grounding resistance of a tower, used to perform the method for measuring the grounding resistance of a tower as described in any one of claims 1-5, characterized in that, include: The network model construction module is used to construct a chain-like linear network model consisting of N towers and their connecting ground wires, where the grounding lead connection point of each tower is defined as a node, and the nodes are connected through ground wire impedance. The prior parameter setting module is used to set the typical engineering value of the grounding impedance of each tower, and to construct the prior admittance matrix based on the typical engineering value of the grounding impedance. The prior impedance matrix is ​​obtained by inverting the prior admittance matrix. The hybrid excitation injection and measurement module is used to inject multiple hybrid excitation current signals of different frequencies into the grounding lead of the tower under test. The synchronous vector measurement device is used to synchronously collect the measured voltage of all nodes, and the phase-locked amplification technology is used to separate the measured voltage at each frequency. The admittance bias calculation module is used to calculate the difference between the true admittance matrix and the prior admittance matrix to obtain the admittance bias matrix. The impedance deviation calculation module is used to calculate the difference between the actual impedance matrix and the prior impedance matrix to obtain the impedance deviation matrix. The linear relationship approximation module is used to establish an approximate linear relationship between the impedance deviation matrix, the admittance deviation matrix, and the voltage difference vector based on the Woodbury matrix identity. The voltage difference vector is the difference between the measured voltage and the prior calculated voltage, and the prior calculated voltage is the product of the prior impedance matrix and the injected excitation current signal. The impedance deviation calculation module is used to solve for an approximate linear relationship and obtain the impedance deviation of the grounding impedance relative to the typical engineering value of the grounding impedance at each frequency. The grounding resistance extraction module is used to calculate the actual grounding impedance based on the impedance deviation of the typical engineering value of the grounding impedance, and to separate the actual grounding impedance to obtain the grounding resistance.

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