A single-ended ground fault locating method based on signal injection method

Abstract

The present application relates to cable positioning technical field, especially to a kind of unidirectional grounding fault positioning method based on signal injection method.The method includes the following steps: installing impedance detection unit at substation grounding knife gap, by built-in injection coil, controllable ac signal is injected to transmission line, so that line is open circuit state;Current signal after injection is collected and frequency enhancement extracts the amplitude and phase of target frequency component;Zero sequence impedance is calculated based on injection voltage and current, and compared with preset impedance model to judge single-phase grounding;When fault is detected, the fault distance, tower position and grounding phase are determined according to impedance difference matching result, to realize accurate positioning.The present application realizes high sensitivity detection, high stability signal extraction and high precision positioning of single-phase grounding fault by injecting controllable ac signal in transmission line and combining frequency enhancement, phase self-calibration and impedance difference matching analysis.

Description

Technical Field

[0001] This invention relates to the field of cable location technology, and in particular to a method for locating unidirectional grounding faults based on signal injection. Background Technology

[0002] To ensure the safe operation of the power grid, the rapid and accurate location of single-phase grounding faults has always been a crucial issue in power system protection and maintenance. Existing technologies for single-phase grounding fault location mainly include current-voltage ratio methods, zero-sequence current methods, and impedance measurement-based fault location methods. Among these, impedance measurement methods, which determine the fault location by measuring changes in line impedance, are a commonly used method. Traditional impedance measurement methods typically rely on passive acquisition of normal operating current and voltage signals, or on inspection vehicles or portable injection devices for local fault detection. These methods have the following subtle but critical drawbacks: Because traditional methods rely on operating current signals, the zero-sequence current generated by small grounding faults or high-resistance grounding faults is weak and easily masked by normal operating fluctuations or external interference, leading to unstable measurement results. Furthermore, in long-distance transmission lines, due to uneven distribution of line length, capacitance, and inductance, as well as external electromagnetic interference, the phase of the zero-sequence current is prone to shift, affecting the accuracy of impedance calculation and fault location. Summary of the Invention

[0003] Therefore, it is necessary to provide a unidirectional grounding fault location method based on signal injection to solve at least one of the above-mentioned technical problems.

[0004] To achieve the above objectives, a unidirectional ground fault location method based on signal injection is provided, the method comprising the following steps:

[0005] Step S1: Install an impedance detection unit at the grounding switch of the substation of the transmission line, wherein the detection unit has a built-in electromagnetic coupling injection coil and a current sensor;

[0006] Step S2: Inject an AC signal into the transmission line through the injection coil and control the injection amplitude and frequency to make the circuit of the transmission line open.

[0007] Step S3: Acquire the injected current signal based on the open circuit state, and perform frequency enhancement on a specific frequency of the current signal to extract the amplitude and phase of the target frequency component;

[0008] Step S4: Calculate the zero-sequence impedance of the line based on the amplitude and phase of the injected voltage and current, and compare it with the preset line impedance model to determine whether there is a single-phase grounding and obtain the impedance difference matching result.

[0009] Step S5: When a grounding fault is detected, determine the fault distance or tower location based on the impedance difference matching result, and output the grounding phase and location information.

[0010] The present invention has the following beneficial effects:

[0011] I. By installing an impedance detection unit integrating an electromagnetic coupling injection coil and a current sensor at the grounding switch of a substation on a transmission line, a controllable AC signal can be actively injected without interrupting line operation, enabling accurate signal response analysis under open-circuit conditions. By adjusting the amplitude and frequency of the injected signal, the zero-sequence channel exhibits significant impedance change characteristics within a specific frequency range, thereby improving the sensitivity for identifying weak grounding currents or high-resistance grounding faults. Compared with traditional passive detection methods, this method has the advantages of strong anti-interference capability and high measurement accuracy, and can reliably identify single-phase grounding faults under complex operating conditions.

[0012] Second, in the signal acquisition and processing process, this invention achieves self-calibrated amplification and amplitude smoothing of the target frequency component by segmenting and averaging the injected current signal into micro-period segments and constructing an amplification factor based on the phase difference between adjacent period segments. This "frequency enhancement-phase synchronization" mechanism can significantly suppress random noise and instantaneous phase jitter, ensuring stable and reliable current amplitude and phase information at different injection frequencies. Furthermore, when calculating the zero-sequence complex impedance of the line, its zero-sequence resistance and reactance components can maintain continuous characteristics in both the amplitude and phase domains, making the zero-sequence impedance characteristic data have good comparability and anti-interference capabilities, providing high-quality data support for subsequent impedance difference analysis.

[0013] Third, based on zero-sequence impedance analysis, this invention constructs a frequency response direction discrimination model by combining the phase deviation variation law of the injected signal and the returned signal. By detecting the phase response reversal phenomenon in a specific frequency range, and calculating the impedance change rate based on the amplitude difference and frequency interval before and after phase reversal, the existence and specific location of a single-phase ground fault can be intuitively determined. This method can maintain consistent positioning accuracy under different line lengths and different grounding resistances, avoiding the sensitivity of traditional algorithms to line parameter estimation errors. Simultaneously, through a dual verification mechanism of impedance difference matching and phase reversal analysis, rapid identification of fault distance and grounding phase is achieved, significantly improving the reliability and practicality of locating single-phase ground faults. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the steps of a unidirectional grounding fault location method based on signal injection.

[0015] Figure 2 for Figure 1 A detailed flowchart illustrating the implementation steps of step S3.

[0016] Figure 3This is a schematic diagram of the transmission line impedance detection method based on the signal injection method for locating unidirectional grounding faults according to this application.

[0017] Figure 4 This is a flowchart of a transmission line fault location method based on signal injection for unidirectional grounding fault location according to this application.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical method of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor methods and / or microcontroller methods.

[0021] It should be understood that although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are used merely to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] To achieve the above objectives, please refer to Figures 1 to 4 A method for locating unidirectional ground faults based on signal injection, the method comprising the following steps:

[0023] Step S1: Install an impedance detection unit at the grounding switch of the substation of the transmission line, wherein the detection unit has a built-in electromagnetic coupling injection coil and a current sensor;

[0024] In one embodiment, to achieve accurate location of grounding faults in transmission lines, an impedance detection unit can be installed at the grounding switch of the substation of the transmission line to realize signal injection and response signal acquisition.

[0025] Preferably, the impedance detection unit is fixedly installed at the connection between the grounding switch and the grounding busbar, and is electrically isolated from the switch body by an insulating mounting bracket to avoid interference to the normal grounding circuit during the signal injection process.

[0026] During installation, firstly, select the matching impedance detection unit model based on the rated voltage level of the transmission line and the impedance range of the grounding loop; secondly, connect the input terminal of the detection unit to the signal injection control terminal of the substation, and connect its output terminal to the grounding lead terminal to ensure the closure of the signal injection path and the return path.

[0027] In some preferred embodiments, the impedance detection unit integrates an electromagnetic coupling injection coil and a current sensor. The electromagnetic coupling injection coil is used to inject a detection signal with a specific frequency or pulse characteristics into the grounding loop of the transmission line; the current sensor is used to monitor the current response signal in the grounding loop in real time so as to calculate the impedance characteristics later.

[0028] Furthermore, the electromagnetic coupling injection coil adopts a toroidal multi-turn winding structure, forming magnetic coupling with the grounding conductor in a non-contact manner, thereby achieving signal injection without disrupting the original grounding continuity state; the current sensor adopts a Hall effect or mutual inductance current detection component, which can perform high-sensitivity sampling of weak signal responses.

[0029] After installation, insulation resistance testing and signal channel calibration are performed on the impedance detection unit to ensure that the injected signal amplitude, frequency, and detection response signal all meet the preset test specifications.

[0030] Step S2: Inject an AC signal into the transmission line through the injection coil and control the injection amplitude and frequency to make the circuit of the transmission line open.

[0031] In one embodiment, in order to perform characteristic detection on the grounding loop of a transmission line, an AC signal is injected into the transmission line using an injection coil. By precisely controlling the signal amplitude and frequency, the loop of the transmission line is made to present a measurable open circuit state, which facilitates subsequent impedance change analysis.

[0032] Preferably, the injection coil is an electromagnetic coupling coil installed at the grounding switch, and is electrically connected to the signal source device through a signal injection control module. The signal source device can output AC detection signals of different amplitudes and frequencies, with its frequency range typically set between tens of hertz and thousands of hertz to meet the detection requirements under different transmission line lengths and impedance characteristics.

[0033] During execution, the signal injection control module first receives system control commands and selects appropriate signal parameters based on the line number, detection mode, and environmental interference. Then, it loads the set signal parameters (including amplitude, frequency, and waveform type) into the injection coil, causing the injection coil to generate a specific magnetic field in a short time. The AC signal is then injected into the grounding circuit of the transmission line through electromagnetic coupling.

[0034] To prevent the injected signal from interfering with the normal operation of the line, a low-energy, short-cycle pulsed AC signal is preferred, and anti-reflection filtering units are set before and after the injected signal to ensure that the injected signal only acts on the detection path and does not feed back to the main power grid.

[0035] During signal injection, the system monitors the changes in loop voltage and current response in real time and calculates the transient impedance of the line through the signal sampling module. When the line impedance reaches the set threshold and the signal waveform shows a stable high-impedance characteristic, it indicates that the transmission line loop is in an open-circuit state, signifying that the injection process has met the detection requirements.

[0036] Furthermore, to ensure testing accuracy, the signal injection amplitude control module can automatically adjust the output voltage amplitude according to the change in line loop impedance, so that the electromagnetic coupling effect of the injected signal is kept in the optimal operating range, avoiding signal distortion due to too low amplitude or misjudgment due to too high amplitude.

[0037] In another embodiment, reference can be made to Figure 4 The injection frequency is set to 50Hz-5KHz, the peak frequency is adjustable, the sampling rate is greater than or equal to 20KHz, and the accuracy requirement is less than or equal to 0.5%.

[0038] Step S3: Acquire the injected current signal based on the open circuit state, and perform frequency enhancement on a specific frequency of the current signal to extract the amplitude and phase of the target frequency component;

[0039] In one embodiment, in order to accurately extract the injection response characteristics of the transmission line in the open-circuit state, the current signal in the open-circuit state can be collected and frequency enhanced based on a preset signal injection method.

[0040] Preferably, when the transmission line is in an open-circuit state, the control signal injection module injects an electromagnetic excitation signal of a specific frequency into the line grounding branch, and the current sensor in the impedance detection unit collects the injected current signal in real time. The current signal is digitized by the analog-to-digital conversion module to form an original current response data sequence.

[0041] During the acquisition process, in order to avoid the influence of electromagnetic interference on the target frequency response, a low-noise filter and sampling synchronization mechanism can be applied to the acquisition channel to make the sampling frequency an integer multiple of the injected signal frequency, so as to ensure frequency resolution and phase accuracy.

[0042] In a preferred embodiment, frequency domain analysis is performed on the acquired current signal. First, a Fast Fourier Transform is performed on the original current signal to obtain the amplitude and phase distribution of each frequency component. Then, frequency enhancement processing is performed on a specific frequency component that matches the frequency of the injected signal. The frequency enhancement processing includes: applying a weighted window function to a narrow band region near the target frequency in the frequency domain to suppress the influence of non-target frequency components; and improving the energy response of the target frequency component through a power spectral density enhancement algorithm, so that the target frequency component exhibits a significant amplitude peak in the spectrum.

[0043] After enhancement, the amplitude and phase information of the enhanced target frequency components are extracted, and the amplitude and phase are sampled and averaged multiple times to eliminate fluctuation errors caused by random noise, and finally stable target frequency amplitude and phase data are generated.

[0044] In practical applications, the amplitude and phase of the extracted target frequency components can be used to characterize the impedance change characteristics of the grounding branch of the transmission line, providing basic frequency characteristic parameters for subsequent unidirectional grounding fault location algorithms.

[0045] Step S4: Calculate the zero-sequence impedance of the line based on the amplitude and phase of the injected voltage and current, and compare it with the preset line impedance model to determine whether there is a single-phase grounding and obtain the impedance difference matching result.

[0046] In one embodiment, in order to accurately determine a single-phase grounding fault in a transmission line, the zero-sequence impedance of the line can be calculated based on the amplitude and phase information of the injected voltage and current signals collected by the detection unit, and then compared and analyzed in conjunction with a preset line impedance model.

[0047] Preferably, during the detection phase, the signal injection control device periodically injects a detection voltage signal of a specific frequency into the grounding loop of the transmission line, while the impedance detection unit simultaneously measures the corresponding current response signal. By synchronously sampling the amplitude and phase of the voltage and current signals, the phase difference and amplitude ratio of the voltage and current are obtained, thereby calculating the actual zero-sequence impedance of the line.

[0048] To ensure calculation accuracy, the acquired signals are denoised and phase reference corrected before calculation. The denoising method uses bandpass filtering to eliminate power frequency interference and high-frequency noise, while the reference correction uses a reference signal source to ensure the consistency of voltage and current sampling phase.

[0049] In a preferred embodiment, after the zero-sequence impedance of the line is calculated, it is compared and analyzed with a preset line impedance model stored in the control unit. The preset line impedance model is established based on the line length, conductor cross-section, ground resistivity, and grounding device parameters under normal operating conditions, and is used to reflect the zero-sequence impedance distribution characteristics under fault-free conditions.

[0050] During the comparison process, when the amplitude or phase of the actual zero-sequence impedance deviates from the threshold range of the preset line impedance model, it is determined that the line has a tendency to experience a single-phase ground fault. Furthermore, by calculating the impedance difference between the two, impedance difference matching result data is obtained.

[0051] In some preferred embodiments, the impedance difference matching results include the difference amplitude, phase offset, and matching confidence index, where the matching confidence index is used to quantify the reliability of the detection results. When the matching confidence index is higher than a preset reliability threshold, a single-phase ground fault determination result can be output.

[0052] In another embodiment, reference can be made to Figure 3 At the substation at the transmitting end of the transmission line, the control device injects a specific frequency detection voltage signal into the line grounding circuit through switches such as QS12, QF1, and QS11. At the substation at the receiving end of the transmission line, a switch such as QS20 ensures the closure of the injection circuit, and an impedance detection unit is simultaneously connected to measure the line current response signal. Meanwhile, at intermediate nodes of the transmission line, an impedance detection unit connected to the grounding wire via QS10 collects current signals to ensure that the measured voltage and current signals cover the entire line.

[0053] The acquired voltage and current signals are synchronously sampled to obtain amplitude and phase information, thereby calculating the phase difference and amplitude ratio between voltage and current. To ensure calculation accuracy, the acquired signals are denoised (e.g., using bandpass filtering to eliminate power frequency interference and high-frequency noise) and phase reference is corrected (using a reference signal source to ensure that the voltage and current sampling phases are consistent).

[0054] Based on the processed voltage and current signals, the actual zero-sequence impedance of the transmission line is calculated. The calculated zero-sequence impedance is then compared and analyzed with a preset line impedance model stored in the control unit. This model, based on line length, conductor cross-section, ground resistivity, and grounding device parameters, reflects the zero-sequence impedance characteristics of the line under fault-free conditions.

[0055] When the amplitude or phase of the actual zero-sequence impedance deviates from the threshold range of the preset line impedance model, it is determined that the transmission line has a tendency to experience a single-phase grounding fault. The impedance difference is further calculated to generate impedance difference matching results, including the difference amplitude, phase offset, and matching confidence index. If the matching confidence is higher than the preset reliability threshold, the single-phase grounding fault determination result can be output to the output line status determination terminal.

[0056] Step S5: When a grounding fault is detected, determine the fault distance or tower location based on the impedance difference matching result, and output the grounding phase and location information.

[0057] In one embodiment, when the impedance detection unit of the transmission line detects a ground fault signal, the system can perform a difference matching analysis based on the pre-collected normal operating impedance reference value and the impedance measurement value under the current fault state to determine the fault location.

[0058] Preferably, the current response signal collected by the impedance detection unit at the grounding switch is first obtained, and the zero-sequence impedance change is calculated based on the characteristics of the injected signal; by comparing the change with the preset impedance reference model between different towers, the impedance difference matching result is generated.

[0059] In some preferred embodiments, impedance difference matching results can be mapped to tower distances or specific tower numbers to determine the approximate location of a ground fault. For example, the matching results can be converted into tower distances or fault tower numbers calculated from the substation, based on the linear or nonlinear characteristics of impedance increments with distance.

[0060] At the same time, you can refer to Figure 4 Based on the impedance differences of conductors in different phases, the phase information of the grounding fault can be determined, including single-phase grounding faults of phase A, phase B, or phase C. The impedance detection unit can simultaneously acquire the response signals of each phase through multi-channel sampling, thus achieving phase identification.

[0061] Furthermore, to improve positioning accuracy, impedance difference matching results can be jointly analyzed with historical fault data, line topology information, and tower spacing data. A weighted algorithm or least-squares fitting method can be used to optimize fault location estimation, yielding precise tower locations. Finally, the fault phase, tower location, or fault distance information is output through the monitoring or control terminal, providing operators with real-time ground fault location results for rapid troubleshooting and handling of ground faults.

[0062] As an example of the present invention, reference is made to Figure 2 As shown, step S3 in this example includes:

[0063] Step S31: Acquire the injected current signal based on the open-circuit state to obtain open-circuit current signal data;

[0064] Step S32: Divide the open-circuit current signal data into several micro-period segments according to the injection time, and average and superimpose the open-circuit current signal data in each micro-period segment to obtain the periodic average current signal data.

[0065] Step S33: Perform self-calibration amplification on specific frequency components of the periodic average current signal data based on the phase difference of open-circuit currents in adjacent micro-period segments to generate frequency-enhanced signal data.

[0066] Step S34: Extract the amplitude and phase of the target frequency component from the frequency enhancement signal data.

[0067] In one embodiment, the impedance detection unit is installed at the grounding switch of the transmission line substation, and incorporates a current sensor and a data acquisition module. In the open-circuit state, the impedance detection unit continuously samples the injected current signal and converts the sampled analog current signal into a digital signal, generating open-circuit current signal data. During the acquisition process, each sampling point is accompanied by a timestamp to record the sampling time. After data acquisition is complete, the open-circuit current signal can be processed for baseline drift correction, noise filtering, and transient spike smoothing to generate an open-circuit current signal set for subsequent analysis.

[0068] During the acquisition process, current signals can be repeatedly acquired at different injection frequencies to form a multi-frequency signal dataset, and the sensor status can be recorded in real time, marking abnormal data points. The acquired open-circuit current signals can be used for periodic averaging, frequency enhancement, and amplitude and phase analysis.

[0069] In some embodiments, the open-circuit current signal obtained in step S31 is divided into several micro-period segments according to the injection signal period, with each micro-period segment covering a complete injection period. The sampling points within the micro-period segments are processed by averaging or weighted averaging to generate periodic average current signal data. During the processing, abnormal sampling points can be removed or corrected according to the amplitude fluctuation range, and the periodic average signals of different frequency bands can be processed independently.

[0070] During the micro-period division and averaging process, the amplitude, phase, and timestamp information of each period segment are recorded for subsequent phase self-calibration and frequency enhancement processing. The period-averaged signal can be referenced and calibrated using historical data to ensure the consistency of the period-averaging results in continuous sampling.

[0071] In some embodiments, the target frequency component in the periodically averaged signal is identified by analyzing the open-circuit current phase difference between adjacent micro-period segments, and then self-calibrated and amplified. For different frequency components, a gain coefficient can be set and adaptively adjusted according to the amplitude and phase deviation, thereby enhancing the stability of the target frequency component signal. The self-calibration amplification process can be performed iteratively and combined with multi-point spatial acquisition data for calibration to reduce the impact of local interference or sensor errors.

[0072] During frequency enhancement processing, non-target frequency components can be further filtered and denoised, and amplitude and phase changes over time can be recorded for subsequent amplitude and phase extraction. The enhanced signal can be corrected by combining historical frequency characteristics to form frequency-enhanced signal data.

[0073] In some embodiments, the amplitude and phase of the target frequency component are extracted from the frequency enhancement signal obtained in step S33. The amplitude and phase information are timestamped at each sampling point and can be used to analyze current response characteristics. Multi-cycle statistics can be performed on the amplitude and phase data, including calculating the average, maximum, standard deviation, and trend changes, and generating spatial distribution data. The extracted amplitude and phase data can be matched with a preset impedance model for analysis, and information related to the ground fault phase and tower location can be recorded to form a complete amplitude and phase dataset.

[0074] Preferably, the specific frequency is a pre-set critical operating frequency of the current signal, and the target frequency is the signal component corresponding to the specific frequency. Step S33 includes:

[0075] The instantaneous phase shift is calculated by performing differential analysis on the current phase change between adjacent micro-period segments.

[0076] An amplification factor is constructed based on the instantaneous phase offset, where the amplification factor is used to characterize the magnitude amplification and phase synchronization correction of the target frequency component.

[0077] The amplitude of the target frequency component in the periodic average current signal is phase-synchronized and corrected to obtain the corrected frequency signal.

[0078] The frequency signal after correction is amplified by an amplification factor to obtain frequency-enhanced signal data.

[0079] In one embodiment, and in some embodiments, in the open-circuit state, the impedance detection unit first acquires the current signal injected by the injection coil in real time using a built-in current sensor. The acquisition process includes the following operations: setting the sampling frequency to at least 10 times the target frequency to ensure complete capture of high-frequency and low-frequency component variations; setting the sampling accuracy to 16 bits or higher; and including current amplitude and phase data in the sampling channel. During sampling, each sampling point is accompanied by timestamp information for subsequent micro-period division and phase calculation of the signal. The acquired raw current signal is saved as open-circuit current signal data at microsecond intervals. During the acquisition process, high-frequency interference is attenuated by a built-in filter, and the influence of environmental interference on the signal amplitude is reduced using a differential amplifier circuit. The acquired open-circuit current signal data is saved as a structured data file that can be used for subsequent processing, including current amplitude, phase, and timestamp information.

[0080] Based on the injected signal frequency, the micro-cycle length is set to 1 / 10 to 1 / 5 of the signal period to ensure that each micro-cycle segment can cover the complete cycle of the target frequency. The open-circuit current signal is divided according to the micro-cycle, with each micro-cycle segment including multiple sampling points, retaining amplitude and phase information. Within each micro-cycle segment, the amplitude of the sampling points is averaged, and the average phase is calculated simultaneously to reduce random noise interference. The average amplitude and average phase of each micro-cycle segment are integrated to generate periodic average current signal data, and the corresponding time node information is recorded to prepare for the phase self-calibration in step S33.

[0081] Differential analysis is performed on the current phase change between adjacent micro-period segments to calculate the instantaneous phase offset at each sampling point, and a phase change curve is formed by combining the timestamp. Based on the instantaneous phase offset, an amplitude amplification factor and a phase synchronization correction factor are constructed. The amplitude amplification factor is used to amplify the amplitude of the target frequency signal to ensure signal measurability; the phase synchronization correction factor is used to fine-tune the phase of the target frequency component in each micro-period segment to keep it consistent. The phase of the target frequency component in the periodically averaged current signal is corrected with the amplification factor, and the phase of each micro-period segment is corrected point by point to ensure the continuity of the target frequency signal between each micro-period segment. The corrected frequency signal is amplified point by point using the amplitude amplification factor in the amplification factor to generate frequency-enhanced signal data, while recording the timestamp, amplitude, and phase data. For outliers or noise peaks, weighted averaging or median filtering can be used to ensure that the frequency-enhanced signal data is smooth and continuous.

[0082] Based on the preset target frequency range, a set of corresponding sampling points is selected from the frequency enhancement signal data. The amplitudes of the sampling points for the target frequency components are statistically analyzed, calculating the average amplitude, maximum amplitude, and minimum amplitude, and timestamp information is retained. The phase data of the target frequency components is smoothed, the average phase of each micro-period is calculated, and the phase change trend throughout the entire period is recorded. The amplitude and phase information are integrated to form the target frequency component data, providing a basic input for subsequent ground fault location, including fault distance and grounding phase information.

[0083] Preferably, the frequency signal amplified and corrected by the amplification factor includes:

[0084] The amplitude component is separated from the corrected target frequency signal;

[0085] Multiply the amplitude component by the magnification factor to obtain the magnified amplitude;

[0086] The amplified amplitude is recombined with the phase of the corrected frequency signal to form the amplified frequency signal;

[0087] Amplified frequency signals are smoothed to obtain frequency-enhanced signal data.

[0088] In one embodiment, the instantaneous amplitude of the corrected target frequency signal is extracted to generate an amplitude sequence; simultaneously, the phase information of the corresponding sampling points is retained for subsequent combination. The amplitude of each sampling point in the amplitude sequence is multiplied by a pre-constructed amplification factor to obtain an amplified data sequence. The amplification factor can be calculated based on the instantaneous phase offset of the target frequency signal to ensure consistency between amplitude enhancement and phase synchronization correction. The amplified amplitude sequence is combined point-by-point with the phase data of the corrected target frequency signal to generate an amplified frequency signal sequence, maintaining the original timestamp correspondence. The generated amplified frequency signal sequence is smoothed, for example using a moving average, weighted moving average, or median filtering method, to eliminate amplitude abrupt changes or noise peaks, obtaining the final frequency-enhanced signal data.

[0089] In some embodiments, the window length for amplitude smoothing can be set according to the sampling rate and the target frequency period, for example, to 1 / 5 to 1 / 10 of the target frequency period, in order to balance the smoothing effect and the signal response speed.

[0090] Preferably, recombinating the amplified amplitude with the phase of the corrected frequency signal includes:

[0091] Identify the time axis of the corrected frequency signal and divide the corrected frequency signal into several continuous time windows according to the time axis, where the amplitude change within each time window is regarded as a segment;

[0092] A time window is randomly selected as the first time window, and the peak position of the frequency signal amplitude within the first time window is aligned with the local maximum or minimum value of the phase of the frequency signal in that segment to obtain the first segment fine-tuning result;

[0093] The second time window is obtained by using the adjacent window of the first time window as the second time window and adjusting the phase of the frequency signal in the second time window by using the amplified amplitude.

[0094] The phase of the corrected frequency signal is recombined with the results of the first and second segment fine-tuning to obtain the amplified frequency signal.

[0095] In one embodiment, the time axis of the corrected frequency signal is first confirmed, and the signal is divided into several continuous time windows according to the time axis. Each time window corresponds to a relatively stable segment of the signal amplitude. The specific steps are as follows: the corrected frequency signal is divided into multiple continuous time windows according to a preset sampling rate and target frequency period. The amplitude change within each window is regarded as a single segment for fine-tuning.

[0096] A random time window is selected as the first time window. Within this window, the peak position of the frequency signal amplitude is identified, and this peak position is aligned with the local phase extrema (maximum or minimum value) of the corresponding segment, generating the first segmental fine-tuning result. This operation ensures that the amplified signal remains synchronized with the original phase information. The adjacent time window of the first time window is used as the second time window. By referring to the first segmental fine-tuning result, the amplified amplitude is applied to the phase adjustment of the frequency signal in the second window, obtaining the second segmental fine-tuning result. This step can be performed sequentially for subsequent time windows in chronological order.

[0097] The fine-tuning results of all time windows are combined according to the original time series, and the amplitude and corresponding phase information of each time window are reintegrated to form a complete amplified frequency signal, maintaining time continuity and amplitude-phase consistency.

[0098] In some embodiments, the combined frequency signals may be further smoothed to reduce amplitude and phase abrupt changes across the window, generating final frequency-enhanced signal data for subsequent target frequency component extraction and fault analysis.

[0099] Preferably, step S4 includes the following steps:

[0100] Step S41: Calculate the corresponding complex impedance components based on the amplitude and phase of the injected voltage and current, and decompose the complex impedance components into zero-sequence resistance components and zero-sequence reactance components.

[0101] Step S42: Generate line zero-sequence impedance characteristic data based on the ratio of zero-sequence resistance component to zero-sequence reactance component;

[0102] Step S43: Perform differential comparison between the zero-sequence impedance characteristic data of the line and the preset line impedance model in the amplitude domain and phase domain respectively to obtain impedance offset data;

[0103] Step S44: Determine whether there is a single-phase grounding based on the impedance offset data and obtain the impedance difference matching result.

[0104] In one embodiment, based on the amplitude and phase information of the injected voltage and current signals, the acquired voltage and current waveforms are first synchronously sampled and their amplitude and phase extracted. Then, the corresponding complex impedance component is calculated based on the voltage-to-current ratio. The complex impedance component is then decomposed into a zero-sequence resistance component and a zero-sequence reactance component, where the zero-sequence resistance component represents the resistance characteristics of the grounding path, and the zero-sequence reactance component represents the reactance characteristics of the grounding path. The decomposed zero-sequence resistance and zero-sequence reactance can be arranged into a time-series data sequence according to the sampling time order, which serves as the input for subsequent feature analysis.

[0105] By proportionally calculating the zero-sequence resistance and zero-sequence reactance components, characteristic data of the line's zero-sequence impedance is generated. For example, the ratio of zero-sequence resistance to zero-sequence reactance, and the combined characteristics of amplitude and phase can be calculated to characterize the impedance variation of the line under different grounding conditions. The generated characteristic data of the line's zero-sequence impedance can include information such as amplitude sequence, phase sequence, and phase angle variation trend, providing basic data for grounding fault identification.

[0106] The zero-sequence impedance characteristic data of the line is differentially compared with the preset line impedance model. The differential comparison includes calculating the offset between the actual measured data and the model data in the amplitude domain and the phase domain, respectively, to obtain the impedance amplitude offset sequence and the phase offset sequence; the offset sequence is statistically or smoothly processed to reduce the influence of measurement noise, thereby obtaining stable impedance offset data for judging line anomalies.

[0107] Single-phase grounding is determined based on impedance offset data. The specific operation includes: analyzing whether the amplitude and phase changes of the impedance offset data exceed preset thresholds; if so, a single-phase grounding is determined. Simultaneously, impedance difference matching results can be generated based on the amplitude deviation and phase difference to further locate the faulty tower or line segment. The impedance difference matching results may include the single-phase grounding phase, the fault distance range, and the faulty tower number, for subsequent alarm or fault handling.

[0108] Preferably, step S42 includes:

[0109] Based on the proportional relationship between the zero-sequence resistance component and the zero-sequence reactance component, the amplitude of the zero-sequence resistance component is adjusted, and the phase of the zero-sequence reactance component is corrected.

[0110] The proportionality coefficient is calculated based on the adjusted zero-sequence resistance component and the corrected zero-sequence reactance component to obtain the zero-sequence impedance ratio.

[0111] The stable range of the proportional relationship is determined based on the continuous change of the zero-sequence impedance ratio, and representative impedance characteristics are extracted within this stable range to obtain the zero-sequence impedance characteristic data of the line.

[0112] In one embodiment, the amplitude of the zero-sequence resistance component is first adjusted based on the ratio between the zero-sequence resistance component and the zero-sequence reactance component, and the phase of the zero-sequence reactance component is corrected to ensure a more accurate relationship between the amplitude and phase of the zero-sequence impedance. The specific implementation steps are as follows: acquire the signal data of the zero-sequence resistance component and the zero-sequence reactance component of the current line; calculate the adjustment amount of the resistance amplitude according to the theoretical ratio between the zero-sequence resistance and the zero-sequence reactance, and apply it to the zero-sequence resistance component to reduce the amplitude deviation; correct the phase of the zero-sequence reactance component to correct the phase drift caused by line parameters or measurement noise, ensuring that the amplitude and phase of the zero-sequence impedance remain consistent.

[0113] The ratio of the adjusted zero-sequence resistance component to the corrected zero-sequence reactance component is calculated to obtain the zero-sequence impedance ratio, which is the amplitude proportionality coefficient of the zero-sequence impedance. The change of the ratio value over time or at sampling points is recorded to facilitate subsequent analysis of the stability of the proportional relationship.

[0114] The continuous variation trend of the zero-sequence impedance ratio is analyzed to determine the interval in which it remains relatively stable over time or in the sampling sequence. Representative impedance characteristics, including amplitude characteristics, phase characteristics and their variation range, are extracted within the stable interval to generate zero-sequence impedance characteristic data of the line, which is used for subsequent fault judgment or line status analysis.

[0115] In some embodiments, the zero-sequence impedance ratio may be smoothed or outliers may be removed to ensure that the extracted impedance feature data is more accurate and stable.

[0116] Preferably, decomposing the complex impedance component into a zero-sequence resistance component and a zero-sequence reactance component includes: performing polar coordinate decomposition on the complex impedance component and extracting the zero-sequence resistance component and the zero-sequence reactance component respectively.

[0117] In one embodiment, the complex impedance component data of the transmission line is first acquired. This complex impedance component data can be measured in real time by an impedance detection unit or obtained through signal processing. Then, the complex impedance components are decomposed into polar coordinates. The specific steps are as follows: the measured complex impedance signal data, including amplitude and phase information, is acquired; the complex impedance signal is filtered and denoised to remove measurement noise and high-frequency interference, ensuring the stability and accuracy of the signal.

[0118] The complex impedance is expressed in polar coordinates as amplitude and phase. Based on the relationship between the amplitude and phase of the complex impedance, the corresponding real and imaginary parts are decomposed using trigonometric functions. The real part corresponds to the zero-sequence resistance component, and the imaginary part corresponds to the zero-sequence reactance component.

[0119] The real part of the data is marked as the zero-sequence resistance component, and the imaginary part of the data is marked as the zero-sequence reactance component. The zero-sequence resistance component and the zero-sequence reactance component obtained by decomposition are recorded in time series for subsequent impedance ratio calculation, amplitude adjustment and phase correction.

[0120] In some embodiments, the zero-sequence resistance component and the zero-sequence reactance component may be normalized to maintain comparability under different sampling conditions and reduce deviations caused by measurement errors.

[0121] Preferably, determining whether a single-phase ground fault exists and obtaining the impedance difference matching result further includes:

[0122] The return current signal is synchronously acquired at the impedance detection unit, and the phase deviation between the injected AC signal and the return current signal is calculated.

[0123] The presence of a single-phase ground fault in the line is determined by the change in directional characteristics between the phase deviation and the injection frequency, and the impedance difference matching result is obtained.

[0124] In one embodiment, after the impedance detection unit is installed at the grounding switch of the transmission line substation, it can simultaneously excite the injected signal and collect the return current signal. The specific steps are as follows: an AC injection signal of a preset frequency is applied to the impedance detection unit, and the return current signal is collected in real time in the loop; the collected return current signal is filtered in the time domain and frequency domain to remove noise and high-frequency interference; the return current signal and the injected AC signal are synchronized in time to ensure accurate phase comparison.

[0125] By representing the injected signal and the returned current signal in complex numbers, the amplitude and phase information of the two are compared; the instantaneous phase deviation between the two is calculated, and the phase difference curve changes over time; repeated sampling can be performed at different injection frequencies to form a correspondence between phase deviation and frequency.

[0126] The directional characteristics of phase deviation as a function of injection frequency are analyzed. When the phase deviation shows a specific regularity, it is determined that there is a single-phase grounding in the line. Based on the changes in the amplitude and directional characteristics of the phase deviation, the impedance difference between each phase is calculated to obtain the impedance difference matching result. The impedance difference matching result is recorded as the basis for fault diagnosis of the line and is used to further determine the faulty phase and location information.

[0127] In some embodiments, the measurement error can be reduced and the accuracy of single-phase grounding determination can be improved by repeatedly injecting signal samples and calculating the average phase deviation.

[0128] Preferably, determining whether a single-phase ground fault exists in the line based on the change in directional characteristics between the phase deviation and the injection frequency change, and obtaining the impedance difference matching result, further includes:

[0129] Based on the directional characteristic changes between phase deviation and injection frequency, the phase response direction sequence at each injection frequency is extracted.

[0130] By comparing the continuity of the phase response direction corresponding to adjacent injection frequencies, it can be determined whether the phase response direction is reversed within a specific frequency range.

[0131] When a phase response direction reversal is detected within a specific frequency range and the reversal amplitude exceeds a preset phase reversal threshold, it is determined that the line has a single-phase grounding characteristic.

[0132] Based on the amplitude difference and frequency interval before and after the phase reversal, the impedance change rate of each phase segment is calculated.

[0133] Based on the sign and magnitude of the rate of change of impedance, impedance difference matching results are generated.

[0134] In one embodiment, the impedance detection unit can apply an AC injection signal within a preset frequency range at the grounding switch of the transmission line and simultaneously acquire the return current signal. The specific steps are as follows: perform amplitude and phase analysis on the injection signal and return current signal at each injection frequency; extract the phase response direction at each injection frequency based on the change of phase deviation with frequency to form a phase response direction sequence; the phase response direction can be discretized into angle values ​​or direction signs for subsequent continuity analysis.

[0135] The phase response directions of adjacent injection frequencies are continuously compared to determine whether a direction reversal occurs within a specific frequency range. When a significant reversal occurs in the phase response direction within a continuous frequency range, the reversal frequency and reversal amplitude are recorded. A preset phase reversal threshold is set. If the reversal amplitude exceeds the threshold, it is marked as a single-phase grounding characteristic range.

[0136] Before and after phase reversal, the change in current amplitude and frequency interval at the corresponding frequency are extracted; based on the amplitude difference and frequency interval, the impedance change rate of each phase segment is calculated to characterize the rapid change of line impedance; the sign and amplitude of the impedance change rate are used to quantify the line impedance characteristics.

[0137] The impedance change rate of each phase segment is integrated to form zero-sequence and phase impedance change characteristic data; based on the sign, amplitude and continuity of the impedance change characteristics, impedance difference matching results are generated for single-phase grounding determination and fault location analysis.

[0138] In some embodiments, the stability and accuracy of phase reversal detection can be improved by scanning different injection frequency points multiple times and taking the average value, thereby obtaining more reliable impedance difference matching results.

[0139] Of particular importance, step S5 includes:

[0140] When a ground fault is detected, the line segment where the fault occurred is determined based on the impedance difference matching results;

[0141] Phase sequence mapping is performed based on the characteristic of impedance difference changing with line length to obtain the distance of the fault point from the measuring end or the corresponding tower position.

[0142] The grounding phase is determined by identifying the distance from the fault point to the measuring end or the corresponding tower position based on the zero-sequence impedance of the line.

[0143] Integrate the distance from the fault point to the measuring end or the corresponding tower location and the fault grounding phase, and output the grounding phase and location information.

[0144] In one embodiment, when the impedance detection unit detects a ground fault in the transmission line, the fault location can be analyzed based on the impedance difference matching results. The specific implementation steps are as follows: Based on the impedance difference matching results, the impedance characteristic data of each measuring point or monitoring point is extracted, including the zero-sequence impedance amplitude, phase, and impedance change rate; the impedance characteristic data of each line segment are compared with a preset reference characteristic template to identify line segments with significant impedance anomalies and mark them as candidate fault line segments; weighted statistics can be performed using multi-frequency injected signal scanning results to improve the accuracy of fault line segment identification.

[0145] Based on the characteristic of impedance difference changing with line length, the phase sequence mapping method is used to calculate the distance from the fault point to the measuring end. For tower-type lines, the fault distance can be mapped to the corresponding tower position to obtain the accurate tower number or fault interval. In some embodiments, historical impedance data and line topology information can be combined to improve the fault point location accuracy.

[0146] By utilizing the zero-sequence impedance characteristics of the line, the distribution relationship between the phase current and the zero-sequence current at the fault point is analyzed; the analysis results are compared with the line phase sequence information to confirm the phase of the fault grounding; the reliability of the grounding phase can be further verified through multiple measurements or multi-frequency analysis.

[0147] The distance from the fault point to the measuring end or the corresponding tower location is integrated with the faulty grounding phase to form complete grounding fault information, including the faulty line segment, specific tower location, and faulty phase; this information is then output to the monitoring terminal or recording device so that maintenance personnel can handle the fault or perform further analysis.

[0148] In some embodiments, impedance data can be continuously collected immediately after a fault is detected, and combined with phase sequence analysis methods, the fault location and grounding phase can be dynamically updated and confirmed.

[0149] Of particular importance is the phase sequence projection based on the characteristics of impedance difference variation with line length, which includes:

[0150] Obtain the impedance differences recorded along the line and arrange them in line order;

[0151] Analyze the amplitude and phase variation characteristics of impedance difference with line length to identify key points of variation;

[0152] Based on the changing trends of key points, determine the range of possible fault locations;

[0153] By combining the continuity of impedance difference and the phase sequence relationship within the interval, the distance from the final fault point to the measuring end or the corresponding tower position is confirmed, and the fault phase and location information are output.

[0154] In one embodiment, impedance difference data at various measuring points along the transmission line can be acquired by an impedance detection unit, and these data can be arranged sequentially according to the line direction to form a line impedance difference sequence. The specific steps are as follows: each detection unit along the line synchronously collects impedance difference data, including zero-sequence resistance component, zero-sequence reactance component, and amplitude and phase information; according to the actual arrangement sequence of the line, the impedance difference data at each measuring point are arranged sequentially to form a continuous impedance difference curve for subsequent analysis.

[0155] The amplitude and phase changes of the impedance difference curve are analyzed to extract abrupt change points or locations of significant amplitude / phase changes as key points. By combining preset thresholds or change rate judgment methods, the locations of impedance abrupt changes or phase reversals can be identified, thereby marking the line sections where faults may occur.

[0156] Based on the changing trends of key points, the impedance difference sequence is segmented and analyzed to determine the faulty line section. In some embodiments, impedance continuity and multi-frequency injected signal characteristics can be combined to narrow down the fault range and improve the positioning accuracy.

[0157] Within the fault zone, by analyzing the continuity of impedance difference and the phase sequence relationship of the line, the distance from the final fault point to the measuring end or the corresponding tower position is calculated; the fault grounding phase is determined according to the phase sequence relationship, and the fault point distance and grounding phase are integrated and output to form complete fault location information.

[0158] In some embodiments, the results of multiple measurements along the line can be averaged or filtered to reduce measurement errors and improve the accuracy of fault location.

[0159] Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the application are intended to be included within the invention.

[0160] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for locating unidirectional grounding faults based on signal injection, characterized in that, Includes the following steps: Step S1: Install an impedance detection unit at the grounding switch of the substation of the transmission line, wherein the detection unit has a built-in electromagnetic coupling injection coil and a current sensor; Step S2: Inject an AC signal into the transmission line through the injection coil and control the injection amplitude and frequency to make the circuit of the transmission line open. Step S3: Acquire the injected current signal based on the open-circuit state, and perform frequency enhancement on a specific frequency of the current signal to extract the amplitude and phase of the target frequency component; wherein, step S3 includes the following steps: Step S31: Acquire the injected current signal based on the open-circuit state to obtain open-circuit current signal data; Step S32: Divide the open-circuit current signal data into several micro-period segments according to the injection time, and average and superimpose the open-circuit current signal data in each micro-period segment to obtain the periodic average current signal data. Step S33: Perform self-calibration amplification on specific frequency components of the periodic average current signal data based on the phase difference of open-circuit currents in adjacent micro-period segments to generate frequency-enhanced signal data. Step S34: Extract the amplitude and phase of the target frequency component from the frequency enhancement signal data; wherein, the specific frequency is the pre-set key operating frequency of the current signal, and the target frequency is the signal component corresponding to the specific frequency. Step S33 includes: The instantaneous phase shift is calculated by performing differential analysis on the current phase change between adjacent micro-period segments. An amplification factor is constructed based on the instantaneous phase offset, where the amplification factor is used to characterize the magnitude amplification and phase synchronization correction of the target frequency component. The amplitude of the target frequency component in the periodic average current signal is phase-synchronized and corrected to obtain the corrected frequency signal. The frequency signal after amplification and correction is amplified by an amplification factor to obtain frequency-enhanced signal data; wherein the frequency signal after amplification and correction by the amplification factor includes: The amplitude component is separated from the corrected target frequency signal; Multiply the amplitude component by the magnification factor to obtain the magnified amplitude; The amplified amplitude is recombined with the phase of the corrected frequency signal to form the amplified frequency signal; Amplified frequency signals are smoothed to obtain frequency-enhanced signal data; this includes recombination of the amplified amplitude with the phase of the corrected frequency signals. Identify the time axis of the corrected frequency signal and divide the corrected frequency signal into several continuous time windows according to the time axis, where the amplitude change within each time window is regarded as a segment; A time window is randomly selected as the first time window, and the peak position of the frequency signal amplitude within the first time window is aligned with the local maximum or minimum value of the phase of the frequency signal in that segment to obtain the first segment fine-tuning result; The second time window is obtained by using the adjacent window of the first time window as the second time window and adjusting the phase of the frequency signal in the second time window by using the amplified amplitude. The phase of the corrected frequency signal is recombined with the results of the first and second segment fine-tuning to obtain the amplified frequency signal. Step S4: Calculate the zero-sequence impedance of the line based on the amplitude and phase of the injected voltage and current, and compare it with the preset line impedance model to determine whether there is a single-phase grounding and obtain the impedance difference matching result. Step S5: When a grounding fault is detected, determine the fault distance or tower location based on the impedance difference matching result, and output the grounding phase and location information.

2. The unidirectional grounding fault location method based on signal injection as described in claim 1, characterized in that, Step S4 includes the following steps: Step S41: Calculate the corresponding complex impedance components based on the amplitude and phase of the injected voltage and current, and decompose the complex impedance components into zero-sequence resistance components and zero-sequence reactance components. Step S42: Generate line zero-sequence impedance characteristic data based on the ratio of zero-sequence resistance component to zero-sequence reactance component; Step S43: Perform differential comparison between the zero-sequence impedance characteristic data of the line and the preset line impedance model in the amplitude domain and phase domain respectively to obtain impedance offset data; Step S44: Determine whether there is a single-phase grounding based on the impedance offset data and obtain the impedance difference matching result.

3. The unidirectional grounding fault location method based on signal injection as described in claim 2, characterized in that, Step S42 includes: Based on the proportional relationship between the zero-sequence resistance component and the zero-sequence reactance component, the amplitude of the zero-sequence resistance component is adjusted, and the phase of the zero-sequence reactance component is corrected. The proportionality coefficient is calculated based on the adjusted zero-sequence resistance component and the corrected zero-sequence reactance component to obtain the zero-sequence impedance ratio. The stable range of the proportional relationship is determined based on the continuous change of the zero-sequence impedance ratio, and representative impedance characteristics are extracted within this stable range to obtain the zero-sequence impedance characteristic data of the line.

4. The unidirectional grounding fault location method based on signal injection as described in claim 2, characterized in that, Decomposing the complex impedance component into zero-sequence resistance and zero-sequence reactance components involves performing polar coordinate decomposition on the complex impedance component and extracting the zero-sequence resistance and zero-sequence reactance components respectively.

5. The unidirectional grounding fault location method based on signal injection according to claim 2, characterized in that, Determining whether a single-phase ground fault exists and obtaining impedance difference matching results also includes: The return current signal is synchronously acquired at the impedance detection unit, and the phase deviation between the injected AC signal and the return current signal is calculated. The presence of a single-phase ground fault in the line is determined by the change in directional characteristics between the phase deviation and the injection frequency, and the impedance difference matching result is obtained.

6. The unidirectional grounding fault location method based on signal injection according to claim 5, characterized in that, Determining whether a single-phase ground fault exists in a line and obtaining impedance difference matching results based on the directional characteristic change between phase deviation and injection frequency variation also includes: Based on the directional characteristic changes between phase deviation and injection frequency, the phase response direction sequence at each injection frequency is extracted. By comparing the continuity of the phase response direction corresponding to adjacent injection frequencies, it can be determined whether the phase response direction is reversed within a specific frequency range. When a phase response direction reversal is detected within a specific frequency range and the reversal amplitude exceeds a preset phase reversal threshold, it is determined that the line has a single-phase grounding characteristic. Based on the amplitude difference and frequency interval before and after the phase reversal, the impedance change rate of each phase segment is calculated. Based on the sign and magnitude of the rate of change of impedance, impedance difference matching results are generated.

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