A double-clip grounding resistance magnetic flux peak factor optimization method

Abstract

This invention discloses a method for optimizing the peak flux factor of dual-clamp grounding resistance, relating to the field of grounding resistance measurement. The method employs a composite frequency excitation consisting of the fundamental frequency and odd harmonics, using the square wave harmonic ratio as an initial reference to optimize the amplitude ratio and phase of each frequency component. A voltage clamp flux model is established, with the fundamental frequency power factor characterizing the grounding loop resistance-inductance state, establishing the correspondence between voltage clamp flux, grounding loop response, and current clamp flux. The peak flux factor of voltage clamp flux, the maximum value of the peak flux factor of current clamp flux, and the amplitude coefficients of higher-order responses are incorporated into a comprehensive optimization objective function, and the optimal parameters are solved numerically. During measurement, an excitation signal is generated based on the optimized parameters, and the current clamp response is demodulated synchronously at multiple frequencies. The grounding resistance is obtained through impedance fitting or frequency point fusion. This invention can reduce the peak flux factor of dual-clamp grounding resistance, improve core utilization, while retaining the effective response of higher-order components, improving measurement stability. The parameters can be pre-calibrated, facilitating engineering implementation.

Description

Technical Field

[0001] This invention relates to the field of grounding resistance measurement technology, and in particular to a method for optimizing the peak flux factor of dual-clamp grounding resistance. Background Technology

[0002] Grounding resistance is a crucial parameter for evaluating the safety status of transmission towers, substation grounding grids, power distribution equipment, and lightning protection grounding devices. Traditional three-electrode or four-electrode methods require auxiliary electrodes, resulting in significant on-site wiring and electrode placement work. Furthermore, the placement of auxiliary electrodes may be limited in mountainous areas, urban roads, dense power line corridors, and under energized operating conditions. The dual-clamp grounding resistance measurement method eliminates the need to disconnect the grounding leads. Typically, an AC induced electromotive force is applied to the grounding circuit using a voltage clamp, and the circuit response signal is detected by a current clamp to calculate the grounding resistance. This method is convenient to operate, requires no auxiliary electrodes, and is suitable for rapid testing of field objects such as transmission towers.

[0003] Traditional dual-clamp grounding resistance measurements often employ single-frequency sinusoidal excitation. Existing technologies also include composite frequency excitation, multi-frequency measurement, frequency sweep measurement, or heterogeneous frequency injection, but these typically focus on increasing the measurement frequency or improving the signal processing, without fully considering the differences in magnetic flux waveforms between voltage clamp and current clamp in dual-clamp measurements. Furthermore, given certain core material, cross-sectional area, and allowable working magnetic flux, it is necessary to conduct optimization research on the effective utilization rate of the core.

[0004] For example, Chinese Patent CN112505416A discloses a method for measuring grounding impedance. The problem it addresses is that traditional grounding impedance measurements require measuring the phase angle between the injected current and the detection voltage, which limits measurement accuracy. This prior art improves measurement accuracy by eliminating the phase angle measurement step through harmonic superposition, but its harmonic parameter settings do not consider the influence of changes in the grounding loop impedance state on the current clamping flux. Therefore, it cannot solve the problem of waveform distortion of the current clamping flux caused by changes in the grounding loop state in the double-clamp method, which in turn affects the core utilization rate.

[0005] For dual-clamp measurement, the change in voltage clamp flux generates an induced electromotive force, which forms a response current through the grounding loop impedance and is then detected by the current clamp. Obviously, the current clamp side flux is not a simple replication of the voltage clamp side flux.

[0006] Especially for grounded objects on transmission towers, the grounding down conductor, grounding electrode structure, and coupling between adjacent grounding electrodes may cause the measurement circuit to exhibit a weakly inductive state. Different measurement objects may produce different current clamping flux waveforms with the same composite frequency excitation. If peak clipping optimization is performed only based on voltage clamping flux, the peak factor of the current clamping flux may still be relatively high.

[0007] Furthermore, existing composite frequency schemes often use fixed values ​​for harmonic parameters or only optimize the voltage clamp side, lacking collaborative optimization methods that take into account the magnetic flux characteristics on both sides of the clamp. Simply reducing the peak factor without considering the response intensity of higher-order components at the current clamp induction output may lead to excessive compression of the amplitudes of higher-order frequency components such as the third and fifth orders, causing the composite frequency excitation to degenerate into near-single-frequency excitation and lose the advantages of multi-frequency measurement; moreover, the optimization parameters usually need to be calculated online, increasing the complexity of field implementation.

[0008] Therefore, it is necessary to study a method for optimizing the peak factor of the magnetic flux of the dual-clamp grounding resistance. Under the condition of composite frequency excitation, the peak factor of the voltage clamp magnetic flux, the maximum value of the peak factor of the current clamp magnetic flux within the grounding object range, and the response amplitude of the high-order frequency component at the current clamp induction output terminal should be considered simultaneously so that the composite excitation parameters can reduce the peak factor of the dual-clamp magnetic flux while retaining the effective measurement response of the high-order frequency component. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a method for optimizing the peak flux factor of dual-clamp grounding resistance, thereby solving the aforementioned problems.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0011] A method for optimizing the peak flux factor of dual-clamp grounding resistance, applied to the measurement of dual-clamp grounding resistance including voltage clamp and current clamp, includes the following steps: S1: Determine the frequency components contained in the composite frequency excitation, set the amplitude ratio and phase variables to be optimized within the normalized variable range, and use the harmonic ratio corresponding to the square wave as the initial reference for optimization. S2: Establish a voltage clamp target flux model with the amplitude ratio and phase of each frequency component as variables; S3: Determine the loop state range of the grounding object under test, and characterize the loop state range with the fundamental frequency power factor; S4: Establish the correspondence between voltage clamping flux, grounding loop response and current clamping flux, and obtain the current clamping flux model under different loop conditions; S5: Based on the voltage clamp target flux and current clamp flux models, calculate the voltage clamp flux peak factor and the maximum value of the current clamp flux peak factor within the range of the object under test; S6: Calculate the higher frequency response amplitude coefficient based on the higher frequency component response of the current clamp induction output terminal; S7: The voltage clamp flux peak factor, the maximum value of the current clamp flux peak factor, and the higher-order response amplitude coefficient are all incorporated into the comprehensive optimization objective function to solve for the optimized amplitude ratio and optimized phase of each frequency component; S8: Generates a composite frequency excitation signal based on the optimized amplitude ratio and optimized phase, and uses it for dual-clamp grounding resistance measurement.

[0012] Preferably, in step S1, the composite frequency excitation includes the fundamental frequency and its odd harmonics, and the amplitude ratio and phase variable range to be optimized and the reference are as follows: Pick or , where the element m in set M represents the m-th frequency component of the fundamental frequency. For example, These represent the amplitude ratios of the third and fifth order magnetic flux components relative to the fundamental frequency magnetic flux component, respectively. The phases of the third and fifth magnetic flux components are respectively, and the optimization variables are: (1) During the optimization process, the amplitude ratios of the third and fifth components are normalized to a normalized range: (2) The range of phase variables is: (3) The odd harmonic ratio corresponding to the square wave can be used as an initial reference: (4) And take the initial phase value: (5) The initial reference values ​​for the optimization variables are: (6) When the composite frequency set takes When the optimization variables are simplified to: (7) The corresponding initial reference can be taken as follows: (8) Preferably, in step S2, the voltage clamp target flux model is: Let the fundamental frequency be denoted as . ,when At that time, the voltage clamp target flux model is: (9) in, This is the fundamental frequency magnetic flux amplitude. These represent the amplitude ratios of the third and fifth order magnetic flux components relative to the fundamental frequency magnetic flux component, respectively. These are the phases of the third and fifth magnetic flux components, respectively.

[0013] Preferably, in step S3, the loop state range of the grounded object under test is represented as follows: The equivalent impedance of the grounding loop at the m-th frequency is expressed as: (10) Where R is the equivalent resistance of the grounding loop, L is the equivalent inductance of the grounding loop, and the power factor describes the resistive-inductive state of the grounding loop: (11) In the embodiment of the grounding object of the transmission tower, take The scope of the grounding loop object for optimized coverage; for other grounding objects, the The range is reset according to the characteristics of the corresponding circuit.

[0014] Preferably, in step S4, a current clamping flux model is established under impedance mode normalization conditions: make but: (12) The current clamping flux amplitude term corresponding to the m-th frequency component is: (13) The phase lag corresponding to the m-th frequency component is: (14) The current clamping flux model is represented as: (15) in, This is the normalized proportionality coefficient.

[0015] Preferably, in step S5, for any periodic signal Its peak factor is defined as: (16) in The voltage clamp flux peak factor is: (17) The maximum value of the current clamp flux peak factor is: (18) in, This is the minimum fundamental frequency power factor corresponding to the range of the grounding object under test.

[0016] Preferably, in step S6, the higher-order response amplitude coefficient is determined based on the higher-order frequency component response of the current clamp induction output terminal. For the m-th frequency component, the amplitude ratio of the higher-order response to the fundamental frequency response is defined as follows: (19) in, Let be the amplitude of the m-th frequency component in the current clamp flux; This represents the amplitude of the fundamental frequency component of the current clamp flux; for the range of the grounding object under test. The amplitude coefficient of the m-th higher-order response is: (20) in, (twenty one) (twenty two) The lower and upper reference values ​​for the m-th high-order response are respectively... (twenty three) The saturation function sat is (twenty four) The lower limit of the target weight, and satisfying In one implementation, take When the higher-order response is lower than When the higher-order response amplitude coefficient decreases; when the higher-order response is located at and When the order is between a certain value and a certain value, the amplitude coefficient of the higher-order response is larger; when the higher-order response exceeds a certain value... At that time, the amplitude coefficient of higher-order responses decreases.

[0017] Preferably, when the composite frequency set is At that time, the combined higher-order response amplitude coefficient of the third and fifth frequency components is: (25) in: (26) The larger the value, the more fully and effectively the third and fifth frequency components respond relative to the fundamental frequency component at the current clamp induction output terminal; in one embodiment, take... When the composite frequency set is When, the comprehensive higher-order inductive response coefficient is taken .

[0018] Preferably, in step S7, the comprehensive optimization objective function is: (27) in, These are the weighting coefficients for the voltage clamp flux peak factor, the maximum value of the current clamp flux peak factor, and the amplitude coefficient of the higher-order response, respectively, and they satisfy the following: (28) In one implementation, it is preferable to .

[0019] Preferably, in step S7, a numerical optimization algorithm is used to comprehensively optimize the objective function. By performing a minimization solution, the optimal parameters are obtained: (29) The numerical optimization algorithm includes particle swarm optimization, genetic algorithm, differential evolution algorithm, simulated annealing algorithm, pattern search algorithm, grid search algorithm, or a combination of the above algorithms.

[0020] Compared to existing technologies, this invention discloses a method for optimizing the peak flux factor of dual-clamp grounding resistance. ① Traditional dual-clamp methods often employ single-frequency sinusoidal excitation. Under certain conditions of material, cross-sectional area, and allowable working magnetic flux, the utilization rate of the iron core is limited. This invention, by optimizing the amplitude ratio and phase of each component in the composite frequency excitation, effectively reduces the peak flux factor of the voltage clamp and current clamp, making the magnetic flux waveform flatter. Under the same conditions, the iron core can carry a higher effective magnetic flux, thereby improving the iron core utilization rate. The reduction in peak flux factor also improves the dynamic range and anti-interference capability of the measurement, making the measurement results more stable and reliable. ② Existing composite frequency excitation schemes mostly focus on increasing measurement frequency points or improving signal processing, without fully considering the differences in magnetic flux waveforms between voltage clamp and current clamp in dual-clamp measurement. In other words, the magnetic flux on the current clamp side is not a simple copy of the magnetic flux on the voltage clamp side. This invention establishes the correspondence between voltage clamp magnetic flux, ground loop response and current clamp magnetic flux, and incorporates the magnetic flux characteristics on both sides into the optimization considerations at the same time, so that the composite excitation parameters can take into account the working characteristics of each clamp, and avoid optimizing only one side and causing the performance of the other side to degrade. ③ The circuits of grounding objects such as transmission towers are not purely resistive, but are affected by the grounding down conductor, the structure of the grounding body and the coupling of adjacent grounding bodies, exhibiting a certain degree of weak inductance. Moreover, the degree of inductance varies among different measurement objects. This invention uses the fundamental frequency power factor to characterize the resistive and inductive state of the grounding circuit, and covers the circuit state range of the target object during the optimization process, so that the optimized excitation parameters can adapt to different grounding objects and ensure the effectiveness of on-site measurements. ④ Simply pursuing a reduction in peak factor may lead to excessive compression of the amplitude of higher frequency components such as the third and fifth orders, causing the composite frequency excitation to degenerate into a near-single frequency excitation, thus losing the advantage of multi-frequency measurement. This invention incorporates the higher response amplitude coefficient into the optimization objective, ensuring that the higher frequency components have sufficient response intensity at the current clamp induction output while reducing the peak factor, thereby preserving the rich information required for multi-frequency fusion measurement. ⑤ The optimization process can be completed in advance during the product factory calibration stage. The optimized parameters are stored in the controller. During field measurement, the instrument directly calls the stored parameters to generate a composite frequency excitation signal without the need for online real-time optimization. This reduces the complexity of field implementation and is conducive to engineering promotion and application. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the method for optimizing the peak flux factor of dual-clamp grounding resistance according to the present invention. Figure 2 The waveforms of voltage clamping flux and current clamping flux under different power factor states of the present invention are shown. Figure 3 This is a convergence curve of the comprehensive optimization objective function of this invention; Figure 4 The waveforms of voltage clamping flux and current clamping flux under different power factor states after optimization according to the present invention are shown.

[0022] Figure 5 This is a performance comparison chart of the three schemes of the present invention: single-frequency, square wave harmonic reference, and comprehensive optimization. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] The dual-clamp grounding resistance measurement includes a voltage clamp and a current clamp. The voltage clamp is used to apply induced excitation to the grounding loop under test, and the current clamp is used to collect the response signal in the grounding loop. The controller generates an excitation signal based on the optimized composite frequency parameters and samples, synchronously demodulates, and calculates the grounding resistance from the current clamp response.

[0025] The complete implementation process of this invention is attached. Figure 1 As shown, it includes the following steps: S1: Determine the frequency components contained in the composite frequency excitation, set the amplitude ratio and phase variables to be optimized within the normalized variable range, and use the harmonic ratio corresponding to the square wave as the initial reference for optimization. S2: Establish a voltage clamp target flux model with the amplitude ratio and phase of each frequency component as variables; S3, determine the loop state range of the grounding object under test, and characterize the loop state range with the fundamental frequency power factor; S4. Establish the correspondence between voltage clamping flux, grounding loop response and current clamping flux to obtain current clamping flux models under different loop conditions. S5. Based on the voltage clamp target flux and current clamp flux models, calculate the voltage clamp flux peak factor and the maximum value of the current clamp flux peak factor within the range of the object under test. S6. Calculate the higher frequency response amplitude coefficient based on the higher frequency component response of the current clamp induction output terminal. S7, the voltage clamp flux peak factor, the maximum value of the current clamp flux peak factor, and the higher-order response amplitude coefficient are all incorporated into the comprehensive optimization objective function to solve for the optimized amplitude ratio and optimized phase of each frequency component; S8 generates a composite frequency excitation signal based on the optimized amplitude ratio and optimized phase, and uses it for dual-clamp grounding resistance measurement.

[0026] Composite frequency set can be taken or , where the element m in set M represents the m-th frequency component of the fundamental frequency. For example, These represent the amplitude ratios of the third and fifth order magnetic flux components relative to the fundamental frequency magnetic flux component, respectively. The phases of the third and fifth magnetic flux components are respectively, and the optimization variables are: (1) During the optimization process, the amplitude ratios of the third and fifth components are normalized to a normalized range: (2) The range of phase variables is: (3) The odd harmonic ratio corresponding to the square wave can be used as an initial reference: (4) And take the initial phase value: (5) Therefore, the initial candidate solution for the optimization variable can be taken as follows: (6) It should be noted that the initial references mentioned above are only used to provide initial candidate solutions or initial good value paths for optimization, and do not limit the final amplitude ratios and final phases of the cubic and quintic components. The final parameters are determined by the subsequent comprehensive optimization objective function.

[0027] When the composite frequency set takes When the optimization variables are simplified to: (7) The corresponding initial reference can be taken as follows: (8) Determine the fundamental frequency In the field of grounding resistance measurement, it is generally necessary to avoid major power frequency interference. Let its angular frequency be: ,when At that time, the voltage clamp target flux model is: (9) in, The fundamental frequency magnetic flux amplitude To avoid saturation of the double-clamp core, the cross-section of the measuring clamp should be designed based on the peak magnetic flux. Let the effective cross-sectional area of ​​the voltage clamp core be... The maximum permissible operating magnetic flux density is Then its allowable peak magnetic flux is:

[0028] For any periodic signal Its peak factor is defined as: (16) in The peak factor of magnetic flux can be expressed as: Therefore, to ensure that the iron core does not saturate, the following should be true: Therefore, it can be seen that the maximum effective magnetic flux that the iron core can carry is inversely proportional to the peak flux factor; and under the same effective magnetic flux requirement, the required iron core cross-sectional area is directly proportional to the peak flux factor. Thus, reducing the peak flux factor of the voltage clamp can improve the effective magnetic flux utilization level without increasing the iron core cross-sectional area, or reduce the required iron core cross-sectional area under the same effective magnetic flux requirement. For dual-clamp grounding resistance measurement, the above relationship also applies to current clamp iron cores. However, the current clamp is mainly used to detect the response current in the grounding loop, and its magnetic flux waveform is not only related to the composite frequency excitation parameters but also affected by the resistance and inductance state of the grounding loop under test.

[0029] For grounding objects on transmission towers, the grounding loop under test not only includes the equivalent resistance but may also be affected by the grounding down conductor, the structure of the grounding electrode, and the coupling of adjacent grounding electrodes, exhibiting a certain degree of weak inductance. To describe the state of this loop, the equivalent impedance of the grounding loop at the m-th frequency is expressed as: (10) Where R is the equivalent resistance of the grounding loop, and L is the equivalent inductance of the grounding loop. The fundamental frequency power factor is used to represent the resistance-inductance state of the loop. (11) In the embodiment of the grounding object of the transmission tower, take The scope of the grounding loop object for optimized coverage. Among them, This indicates that the grounding loop is approximately purely resistive. This indicates the presence of a certain equivalent inductive component in the grounding loop. For other grounding objects, such as substation grounding grids, power distribution equipment grounding, or lightning protection grounding devices, the setting can be reset according to their loop characteristics. The range.

[0030] A current-clamping flux model is established under the condition of normalization of the fundamental frequency impedance mode. Let but: (12) The current clamping flux amplitude term corresponding to the m-th frequency component is: (13) The phase lag corresponding to the m-th frequency component is: (14) The current clamping flux model is represented as: (15) in, This represents the normalized scaling factor. The above expression shows that the current clamping flux and the voltage clamping flux are not the same. The change in voltage clamping flux first generates an induced electromotive force (EMF), which then passes through the grounding loop impedance to form a response current, finally creating a flux at the current clamping side. Therefore, the amplitude and phase of the third and fifth components at the current clamping side are both affected by the state of the grounding loop.

[0031] Appendix Figure 2 The voltage clamp flux of the approximate square wave is shown with different The waveform differences between the current clamping flux under different conditions are shown in the figure. It can be seen that under the same composite frequency excitation parameters, different grounding loop conditions will change the waveform of the current clamping flux. Obviously, peak clipping optimization based solely on voltage clamping flux cannot guarantee that the peak factor of the current clamping flux will also be in an optimal state.

[0032] For a set of optimization variables The voltage clamp flux peak factor is: (17) The peak factor of the current clamp flux varies with the circuit state of the object under test. Therefore, its maximum value within the range of the object under test is taken as the maximum value of the peak factor of the current clamp flux. (18) in, This represents the minimum fundamental frequency power factor corresponding to the range of the grounding object under test. In the embodiment of the grounding object on a transmission tower, =0.85. Based on the above definition, Used to evaluate the peak clipping effect of voltage clamp flux waveform. Used to evaluate the worst-case scenario of the current clamping flux waveform within the grounded object range.

[0033] However, simply reducing the flux peak factor may result in excessively small amplitudes for the third and fifth components, causing the composite frequency excitation to degenerate into near-single-frequency excitation. To avoid this problem, this embodiment introduces a higher-order response amplitude coefficient to evaluate the effective response of higher-order frequency components at the current-clamp induction output.

[0034] For the m-th frequency component, the amplitude ratio of the higher-order response to the fundamental frequency response is defined as follows: (19) in, Let be the amplitude of the m-th frequency component in the current clamp flux; This represents the amplitude of the fundamental frequency component of the current clamp flux; for the range of the grounding object under test. The amplitude coefficient of the m-th higher-order response is: (20) in, (twenty one) (twenty two) The lower and upper reference values ​​for the m-th high-order response are respectively... (twenty three) The saturation function sat is (twenty four) The lower limit of the target weight, and satisfying In one implementation, take When the higher-order response is lower than When the higher-order response amplitude coefficient decreases; when the higher-order response is located at and When the order is between a certain value and a certain value, the amplitude coefficient of the higher-order response is larger; when the higher-order response exceeds a certain value... At this time, the amplitude coefficient of higher-order responses decreases. (Higher-order response amplitude coefficient) The design philosophy is that when the high-order response is controlled within... and The value should be higher if it falls within a reasonable range, and lower if it falls outside the range.

[0035] for In this case, the comprehensive higher-order response amplitude coefficient is: (25) in: (26) The larger the value, the more fully and effectively the third and fifth frequency components respond relative to the fundamental frequency component at the current clamp induction output terminal; in one embodiment, take... When the composite frequency set is When, the comprehensive higher-order inductive response coefficient is taken This coefficient is used to prevent the optimization results from excessively reducing the high-frequency components.

[0036] In obtaining and Then, construct the comprehensive optimization objective function: (27) in, These are the weighting coefficients for the voltage clamp flux peak factor, the maximum value of the current clamp flux peak factor, and the amplitude coefficient of the higher-order response, respectively, and they satisfy the following: (28) In one implementation, it is preferable to In this objective function, the first two terms are used to reduce the peak flux factor of the voltage clamp and current clamp, while the last term is used to maintain the effective response of high-order frequency components at the current clamp induction output.

[0037] This embodiment can employ a particle swarm optimization algorithm. Minimization can be achieved using genetic algorithms, differential evolution algorithms, simulated annealing algorithms, pattern search algorithms, grid search algorithms, or combinations of these algorithms. After optimization, the following result is obtained: (29) Figure 3 The convergence curve of the objective function synthesized using the particle swarm optimization algorithm is shown. Figure 3 As can be seen, with each iteration, the objective function gradually decreases and tends to stabilize, indicating that the optimization method can obtain stable composite frequency excitation parameters. (See figure.) and The lower the better; a higher H indicates a more reasonable higher-order response. The voltage clamping flux corresponding to the optimization results is related to different... The waveform difference between the current clamp flux under the state is as follows Figure 4 As shown.

[0038] Optimized parameters This can be calculated and stored in the controller during the product's factory calibration phase. During field measurements, the controller calls upon the optimized amplitude ratio and optimized phase to generate a composite frequency excitation reference signal. At that time, the composite frequency excitation reference signal can be expressed as: (30) in, The amplitude coefficient is determined based on the dual-clamp structure and driving capability. The controller generates the actual drive signal based on the overall excitation amplitude coefficient and applies it to the voltage clamp via the power drive module. The voltage clamp induces a composite frequency electromotive force in the grounding loop under test, causing a response current of the corresponding frequency component to be generated in the grounding loop.

[0039] Depend on Figure 5 It is evident that while the approximate square wave harmonic reference scheme reduces the voltage clamping flux peak factor to approximately 1.23, its current clamping flux peak factor within the grounded object range remains high. The maximum value is approximately 2.45, indicating that peak clipping based solely on voltage clamping flux cannot guarantee optimal utilization of the current clamping side core. After optimization, Approximately 1.4882, It drops to approximately 1.5897. Considering the positive correlation between the core cross-sectional area and the peak flux factor, and taking the same weights for the effective flux demand and allowable flux density on both sides, the total equivalent cross-sectional area requirement of the dual-clamp core is... + Proportional to this, the optimized scheme reduces the equivalent cross-sectional area requirement of the double clamp by approximately 19.6% compared to the approximate square wave harmonic reference scheme. Simultaneously, the higher-order response amplitude coefficient H only decreases from approximately 0.56 to 0.556, indicating that the optimization results effectively reduce the current clamp flux peak factor while maintaining a good high-order frequency response. The optimized scheme effectively controls the response of higher-order frequency components by reducing the flux peak factor.

[0040] After the current clamp acquires the response signal, it can synchronously demodulate the fundamental frequency, third frequency, and fifth frequency components to obtain the response results of each frequency component. Subsequently, the corresponding equivalent impedance is calculated based on the response at each frequency point, and the grounding resistance is obtained through frequency point fusion or impedance-inductance fitting.

[0041] The above measurement output process can be achieved using conventional multi-frequency synchronous demodulation and impedance calculation methods. The focus of this invention is on optimizing the peak flux factor of the composite frequency excitation parameters. Through this optimization process, the dual-clamp grounding resistance measurement can reduce the peak flux factor of the voltage clamp and current clamp while retaining the effective response at higher frequencies, thereby improving core utilization and measurement stability.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for optimizing the peak flux factor of dual-clamp grounding resistance, applied to the measurement of dual-clamp grounding resistance including voltage clamp and current clamp, characterized in that, Includes the following steps: S1: Determine the frequency components contained in the composite frequency excitation, set the amplitude ratio and phase variables to be optimized within the normalized variable range, and use the harmonic ratio corresponding to the square wave as the initial reference for optimization. S2: Establish a voltage clamp target flux model with the amplitude ratio and phase of each frequency component as variables; S3: Determine the loop state range of the grounding object under test, and characterize the loop state range with the fundamental frequency power factor; S4: Establish the correspondence between voltage clamping flux, grounding loop response and current clamping flux, and obtain the current clamping flux model under different loop conditions; S5: Based on the voltage clamp target flux and current clamp flux models, calculate the voltage clamp flux peak factor and the maximum value of the current clamp flux peak factor within the range of the object under test; S6: Calculate the higher frequency response amplitude coefficient based on the higher frequency component response of the current clamp induction output terminal; S7: The voltage clamp flux peak factor, the maximum value of the current clamp flux peak factor, and the higher-order response amplitude coefficient are all incorporated into the comprehensive optimization objective function to solve for the optimized amplitude ratio and optimized phase of each frequency component; S8: Generates a composite frequency excitation signal based on the optimized amplitude ratio and optimized phase, and uses it for dual-clamp grounding resistance measurement.

2. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 1, characterized in that, In step S1, the composite frequency excitation includes the fundamental frequency and its odd harmonics. The amplitude ratio and phase variable range to be optimized and the reference are as follows: Pick or In set M, element m represents the m-th frequency component of the fundamental frequency. For example, These represent the amplitude ratios of the third and fifth order magnetic flux components relative to the fundamental frequency magnetic flux component, respectively. The phases of the third and fifth magnetic flux components are respectively, and the optimization variables are: （1） During the optimization process, the amplitude ratios of the third and fifth components are normalized to a normalized range: （2） The range of phase variables is: （3） The odd harmonic ratio corresponding to the square wave can be used as an initial reference: （4） And take the initial phase value: （5） The initial reference values ​​for the optimization variables are: （6） When the composite frequency set takes When the optimization variables are simplified to: （7） The corresponding initial reference can be taken as follows: （8）。 3. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 2, characterized in that, In step S2, the voltage clamp target flux model is: Let the fundamental frequency be denoted as . ,when At that time, the voltage clamp target flux model is: （9） in, This is the fundamental frequency magnetic flux amplitude. These represent the amplitude ratios of the third and fifth order magnetic flux components relative to the fundamental frequency magnetic flux component, respectively. These are the phases of the third and fifth magnetic flux components, respectively.

4. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 1, characterized in that, In step S3, the loop state range of the grounded object under test is represented as follows: The equivalent impedance of the grounding loop at the m-th frequency is expressed as: （10） Where R is the equivalent resistance of the grounding loop, L is the equivalent inductance of the grounding loop, and the power factor describes the resistive-inductive state of the grounding loop: 11） In the embodiment of the grounding object of the transmission tower, take The scope of the grounding loop object for optimized coverage; for other grounding objects, the The range is reset according to the characteristics of the corresponding circuit.

5. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 4, characterized in that, In step S4, a current clamping flux model is established under the condition of impedance mode normalization: make but: （12） The current clamping flux amplitude term corresponding to the m-th frequency component is: （13） The phase lag corresponding to the m-th frequency component is: （14） The current clamping flux model is represented as: （15） in, This is the normalized proportionality coefficient.

6. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 1, characterized in that, In step S5, for any periodic signal Its peak factor is defined as: （16） in The voltage clamp flux peak factor is: （17） The maximum value of the current clamp flux peak factor is: （18） in, This is the minimum fundamental frequency power factor corresponding to the range of the grounding object under test.

7. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 5, characterized in that, In step S6, the higher-order response amplitude coefficient is determined based on the higher-order frequency component response of the current clamp induction output terminal. For the m-th frequency component, the amplitude ratio of the higher-order response to the fundamental frequency response is defined as follows: （19） in, Let be the amplitude of the m-th frequency component in the current clamp flux; This represents the amplitude of the fundamental frequency component of the current clamp flux; for the range of the grounding object under test. The amplitude coefficient of the m-th higher-order response is: (20) in, (twenty one) （22） The lower and upper reference values ​​for the m-th high-order response are respectively... （23） The saturation function sat is (twenty four) The lower limit of the target weight, and satisfying In one implementation, take When the higher-order response is lower than When the higher-order response amplitude coefficient decreases; when the higher-order response is located at and When the order is between 1 and 2, the amplitude coefficient of the higher-order response is larger; when the higher-order response exceeds 1 / 2, the amplitude coefficient of the higher-order response is larger. At that time, the amplitude coefficient of higher-order responses decreases.

8. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 7, characterized in that, When the composite frequency set is At that time, the combined higher-order response amplitude coefficient of the third and fifth frequency components is: （25） in: (26) The larger the value, the more fully and effectively the third and fifth frequency components respond relative to the fundamental frequency component at the current clamp induction output terminal; when the composite frequency set is... When, the comprehensive higher-order inductive response coefficient is taken .

9. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 1, characterized in that, In step S7, the comprehensive optimization objective function is: （27） in, These are the weighting coefficients for the voltage clamp flux peak factor, the maximum value of the current clamp flux peak factor, and the amplitude coefficient of the higher-order response, respectively, and they satisfy the following: （28） In one implementation, it is preferable to .

10. The method for optimizing the peak flux factor of dual-clamp grounding resistance according to claim 9, characterized in that, In step S7, a numerical optimization algorithm is used to comprehensively optimize the objective function. By performing a minimization solution, the optimal parameters are obtained: （29） The numerical optimization algorithm includes particle swarm optimization, genetic algorithm, differential evolution algorithm, simulated annealing algorithm, pattern search algorithm, grid search algorithm, or a combination of the above algorithms.

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