Live-line testing device and method for mutual inductance line parameters and zero-sequence impedance parameters

Abstract

The invention belongs to the field of power transmission line parameter measurement, and discloses a live-line testing device and method for mutual inductance line parameters and zero-sequence impedance parameters. The device comprises a double-circuit line simulation module, a pilot frequency excitation module, a power frequency simulation module, a synchronous acquisition module and a signal processing module. The isolation transformer simulates a double-circuit line, the pilot-frequency power supply provides pilot-frequency excitation signals, the measurement unit realizes synchronous acquisition, and the signal processing module performs anti-interference and amplification processing. The method comprises the steps of line simulation wiring, synchronous time synchronization, pilot frequency signal acquisition, parameter calculation and error verification, and pilot frequency parameters are converted into power frequency parameters by using a frequency conversion formula. According to the invention, power frequency interference can be effectively suppressed in a charged environment, high-precision measurement of zero-sequence impedance and mutual inductance parameters of a mutual inductance line is realized by using pilot frequency excitation and Beidou synchronization technologies, the measurement error is remarkably reduced, the safety and reliability are remarkably improved, and powerful technical support is provided for safe and stable operation of a power system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of transmission line parameter measurement, and particularly relates to a live test device and method for mutual inductance line parameter zero sequence impedance parameters. BACKGROUND

[0002] In the dual-circuit line operation scenario of a high-voltage transmission network, the traditional zero sequence impedance and mutual inductance parameter measurement method faces the bottleneck of serious power frequency interference, insufficient safety, and difficult-to-ensure precision. When one circuit is live and the other circuit is de-energized for maintenance, the power frequency electromagnetic coupling of the live circuit will induce significant interference signals in the de-energized circuit, making the error of the measurement method using power frequency signal injection exceed 5%, and requiring the entire line to be de-energized for the operation, which not only affects the power supply reliability, but also limits the operation and maintenance efficiency.

[0003] At the same time, directly performing power frequency injection and measurement operation under live conditions will increase the risk of electric shock for on-site personnel and may mistakenly trigger protection devices, causing system malfunctions or unplanned shutdowns. In addition, existing synchronous acquisition technologies generally lack high-precision time references, resulting in phase measurement errors greater than 1°, which cannot meet the engineering requirement of controlling impedance measurement error within 1%.

[0004] Although existing research attempts to use an off-frequency excitation method to avoid power frequency interference, the signal conditioning circuit has insufficient anti-interference ability, the off-frequency signal has low synchronization accuracy, and there is a large error when converting off-frequency results to power frequency parameters, which limits the feasibility and popularization of the method in engineering sites. Therefore, there is an urgent need for a device and method that can effectively suppress power frequency interference and achieve high-precision measurement of zero sequence impedance and mutual inductance parameters under de-energized conditions. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a live test device and method for mutual inductance line parameter zero sequence impedance parameters.

[0006] The present application is implemented as follows: a live test device for mutual inductance line parameter zero sequence impedance parameters, characterized in that the live test device for mutual inductance line parameter zero sequence impedance parameters specifically comprises:

[0007] A dual-circuit line simulation module for constructing a simulated dual-circuit transmission line, including an isolation transformer, the primary side and secondary side of the isolation transformer corresponding to the de-energized circuit and the live circuit respectively, the first end and the end of the primary side and the secondary side being provided with taps, and the end taps being grounded;

[0008] An off-frequency excitation module for applying an off-frequency voltage signal to the de-energized circuit, including an off-frequency power supply, the off-frequency power supply outputting a sinusoidal voltage with a frequency of 45Hz and 55Hz;

[0009] A power frequency simulation module, comprising a power frequency power supply and a voltage regulator, wherein the power frequency power supply is used to apply a power frequency voltage signal to the live line;

[0010] A synchronous acquisition module, used for synchronously acquiring the voltage and current signals of the de-energized line and the live line, comprising at least three current-voltage synchronous measurement units, wherein the measurement units are configured with current sensors, voltage sensors and Beidou timing modules;

[0011] A signal processing module, comprising an anti-interference circuit and an amplification circuit, wherein the anti-interference circuit is used to suppress power frequency interference, and the amplification circuit is used to amplify the acquired signals.

[0012] Further, the primary side and the secondary side of the isolation transformer have corresponding line-to-line mutual impedance Z 12 , and the turns ratio of the primary side and the secondary side is 1:1.

[0013] Further, the current sensor is an openable clamp structure, and the voltage sensor is a voltage transformer.

[0014] Further, the anti-interference circuit is a Butterworth wave trap with a center frequency of 50 Hz and an attenuation degree of ≥40 dB; and the amplification circuit is a two-stage programmable gain amplifier with a total amplification multiple of ≤256 times.

[0015] Further, the live-line testing device for mutual inductance line parameters and zero sequence impedance parameters further comprises a safety grounding unit, used to set a grounding protection device at the first end and the last end of the de-energized line.

[0016] Another object of the present application is to provide a live-line testing method for mutual inductance line parameters and zero sequence impedance parameters, comprising the following steps:

[0017] S1, line simulation and wiring: the primary side of the isolation transformer is used as the de-energized line, the first end is connected to an alternating frequency power supply, and the last end is grounded; the secondary side is used as the live line, the first end is connected to a power frequency power supply, and the last end is grounded through a current limiting resistor;

[0018] S2, time synchronization: time synchronization is performed on each measurement unit by using a Beidou timing module;

[0019] S3, alternating frequency signal acquisition: 45Hz and 55Hz alternating frequency voltage signals are sequentially applied to the de-energized line by the alternating frequency power supply, and the voltage and current signals of the first end of the de-energized line and the voltage and current signals of the first end and the last end of the live line are synchronously acquired;

[0020] S4, parameter calculation: the self-impedance of the de-energized line and the mutual impedance of the two-line are calculated according to the acquired alternating frequency signals, and the alternating frequency parameters are converted into power frequency parameters;

[0021] S5, error checking: the measured parameters are compared with the preset parameters to check the measurement error.

[0022] Further, the frequency conversion formula is:

[0023] ;

[0024] Wherein, is the inter-frequency impedance, is 45Hz or 55Hz.

[0025] Further, the self-impedance calculation formula is:

[0026] ;

[0027] The mutual impedance is calculated as

[0028] .

[0029] In combination with the above technical solutions and the technical problems solved, the technical solutions to be protected by the application have the following advantages and positive effects:

[0030] The application can effectively suppress the power frequency interference generated by the live line in the live environment of the live operation of one line and the power-off maintenance of the other line in the double circuit line. The frequency conversion formula and the vector algorithm are used to process the collected inter-frequency signals, and the inter-frequency parameters are converted into power frequency parameters, so as to realize the high-precision measurement of the mutual inductance line zero sequence impedance (self-impedance, mutual impedance) and mutual inductance parameters.

[0031] The application does not need to completely stop the line, and through the electrical isolation of the isolation transformer and the design of the safety grounding unit, the risk of electric shock of the operator and the misoperation of the operating line protection device are effectively avoided, and the safety and reliability of the measurement process are significantly improved, which provides strong and reliable technical support for the safe and stable operation, fault analysis and protection device setting of the power system.

[0032] The application provides a solution for high-precision measurement of mutual inductance line zero sequence impedance and mutual inductance parameters in a live environment, which significantly improves the operation stability and safety of the power system, reduces the power-off time and economic loss caused by line maintenance, and has significant economic and social benefits. It is expected that this technology will have a broad market prospect and commercial value in the fields of power grid companies, power equipment manufacturers and power research institutions.

[0033] Currently, there are no mature technical solutions for live measurement of zero-sequence impedance and mutual inductance parameters of mutual inductance lines, either domestically or internationally. Traditional methods rely on a complete line shutdown, which cannot meet the requirements of modern power systems for continuous power supply and high reliability. The technical solution of this invention, through heterogeneous frequency excitation and satellite synchronous time synchronization technology, achieves high-precision measurement of zero-sequence impedance and mutual inductance parameters of mutual inductance lines under energized conditions, filling a technological gap in this field both domestically and internationally, and providing strong technical support for the safe and stable operation of power systems.

[0034] In power systems, parameter measurement of dual-circuit transmission lines under conditions of both energization and de-energization has always been a technical challenge. Traditional methods, due to problems such as power frequency interference, safety risks, and insufficient measurement accuracy, cannot meet practical needs. The technical solution of this invention effectively solves these problems through innovative device design and method steps, achieving high-precision, safe, and reliable measurement, thus resolving a long-standing technical problem that has plagued the power industry.

[0035] Traditionally, it has been believed that high-precision line parameter measurement in energized environments is impossible or would incur extremely high costs and risks. However, the technical solution of this invention, through the innovative application of heterogeneous excitation and satellite synchronous timing technology, demonstrates the feasibility of high-precision measurement in energized environments, overcomes traditional technical biases, and provides new ideas and methods for online monitoring and fault diagnosis of power systems. Attached Figure Description

[0036] Figure 1 This is a wiring diagram of a double-circuit line simulation module for a live testing device and method for zero-sequence impedance parameters of mutual inductance lines provided in an embodiment of the present invention.

[0037] Figure 2 This is a block diagram illustrating the principle of heterogeneous excitation and synchronous acquisition of the live testing device and method for zero-sequence impedance parameters of mutual inductance lines provided in this embodiment of the invention.

[0038] Figure 3 This is a schematic diagram of the signal conditioning circuit principle of the live testing device and method for zero-sequence impedance parameters of mutual inductance lines provided in an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] Symbol definition:

[0041] Voltage at the beginning of the power outage line: ;

[0042] Current at the beginning of the power outage line: ;

[0043] Phase difference between voltage and current at the beginning of the power outage line: ;

[0044] Voltage at the beginning of the live line: ;

[0045] Current at the beginning of a live line: ;

[0046] Phase difference between voltage and current at the beginning of a live line: ;

[0047] Voltage at the end of the live line: ;

[0048] Self-impedance of the power outage line: ;

[0049] Mutual impedance of the two circuits: ;

[0050] Power frequency impedance parameters: .

[0051] Under the operating conditions of double-circuit lines in high-voltage transmission networks, electromagnetic coupling between energized and de-energized circuits is an inherent phenomenon. Especially in zero-sequence paths, power frequency induction is directly superimposed on the test signal, amplifying impedance measurement errors. Existing measurement methods using power frequency signal injection cannot distinguish between the test signal and interference components, and can only be implemented with the entire line de-energized, significantly impacting the operation and scheduling of the transmission system and power supply reliability. In uninterrupted measurement scenarios, the voltage and current components of power frequency interference typically have higher amplitudes than the inter-frequency test signal, resulting in a lower signal-to-noise ratio. This directly affects the high-precision acquisition of phase and amplitude, a bottleneck that traditional power frequency measurement schemes struggle to overcome.

[0052] This invention constructs a double-circuit line simulation module, using the primary and secondary sides of an isolation transformer to simulate de-energized and energized lines respectively. The inductive reactance values ​​of the primary and secondary sides correspond proportionally to the mutual impedance between the lines, thus equivalently reproducing the coupling characteristics of the actual power grid in the experimental system. The 1:1 turns ratio design of the isolation transformer ensures that the amplitude ratio of the injected and induced signals is consistent with the field conditions, and the actual grounding operation state is simulated through the arrangement of taps at the beginning and end points and the grounding at the end. This physical modeling method ensures that the subsequent evaluation of anti-interference and measurement methods under experimental conditions has engineering equivalence.

[0053] For the introduction of test signals, a heterogeneous frequency excitation module applies sinusoidal voltages of 45Hz and 55Hz to the power outage circuit. These frequencies are staggered from the 50Hz power frequency, allowing for selective retention of the test signal components and attenuation of power frequency interference during subsequent frequency domain filtering. The heterogeneous frequency power supply features programmable frequency and voltage control. Combined with a step-up transformer, it can provide test signals with sufficient amplitude under different line voltage levels and coupling conditions, ensuring a high signal-to-noise ratio for the measurement system under various operating conditions. This process avoids the difficulty of directly extracting signals against a power frequency background, improving anti-interference capabilities from the signal source design perspective.

[0054] To reproduce the actual power frequency coupling effect of a live line on a de-energized line, the power frequency simulation module adjusts the power frequency power supply to the required amplitude and applies it to the secondary side of the isolation transformer via a voltage regulator, effectively simulating the operating voltage of a live line. Therefore, the de-energized circuit, while receiving inter-frequency excitation, is also subjected to power frequency interference signals induced through the isolation transformer. The signal composition under these conditions more closely resembles the complex interference environment in an engineering field. Accurately reproducing this superposition effect under experimental conditions verifies the effectiveness and robustness of the anti-interference circuit and signal processing algorithm.

[0055] The signal acquisition section employs a multi-channel synchronous acquisition system with a BeiDou time synchronization module, ensuring that the sampling time difference between voltage and current measurements across different measurement units is controlled within 100ns, thereby compressing the phase error to the order of 0.01°. Clamp-on current sensors and high-precision voltage transformers perform proportional transformation and isolated output for current and voltage, respectively, guaranteeing measurement accuracy and system safety. This high-precision synchronous acquisition system effectively reduces amplitude and phase errors caused by sampling time differences during impedance calculation, ensuring that the calculation accuracy of zero-sequence impedance and mutual inductance parameters meets the engineering requirement of an error of less than 1%.

[0056] The acquired signal is filtered by a Butterworth notch filter in the signal processing module to remove the 50Hz power frequency component, and then its amplitude is boosted by a two-stage programmable gain amplifier circuit to ensure sufficient resolution for weak heterogeneous signals in subsequent digital processing. The notch filter's center frequency is perfectly matched to the power frequency, with an attenuation greater than 40dB, significantly reducing power frequency interference to background noise levels. The two-stage amplifier circuit dynamically adjusts the gain according to the input signal amplitude, avoiding overload distortion while maximizing the signal-to-noise ratio. The combined effect of these components enables high-precision, safe, and repeatable measurement of the zero-sequence impedance and mutual inductance parameters of a double-circuit line under uninterrupted power conditions.

[0057] like Figure 1 As shown, this embodiment of the invention provides a live-line testing device for the zero-sequence impedance parameter of mutually inducted lines, comprising:

[0058] Double-circuit line simulation module: An isolation transformer is used to simulate a double-circuit transmission line. The primary side of the isolation transformer simulates a de-energized line, and the secondary side simulates a energized line. Taps are set at the beginning and end of both the primary and secondary sides, with the end tap grounded to simulate the grounding conditions of an actual line. The transformation ratio of the primary to secondary sides of the isolation transformer is 1:1, and the inductive reactance values ​​of the primary and secondary sides correspond to the mutual impedance between the lines.

[0059] Inter-frequency excitation module: The inter-frequency power supply is used to apply inter-frequency voltage signals to the de-energized line, with output frequencies of 45Hz and 55Hz. The output voltage can be boosted by a step-up transformer to meet the needs of different testing scenarios. The inter-frequency power supply communicates with the main control unit via an RS-485 interface to achieve programmable adjustment of the output frequency and voltage.

[0060] Power frequency simulation module: The power frequency power supply adopts a 50Hz power frequency power supply. The output voltage is adjusted to 220V by the voltage regulator and then applied to the secondary side of the isolation transformer to simulate the power frequency voltage of the actual operating line.

[0061] Synchronous Acquisition Module: The current and voltage synchronous measurement unit is equipped with an openable clamp-on current sensor and a high-precision voltage transformer. The current sensor is used to acquire the current signal on the secondary side of the current transformer, with a measurement range of 0-30A, and the output voltage is proportional to the current. The voltage transformer is used to acquire the voltage signal of the line, with an accuracy of up to 0.01%. The measurement unit has a built-in Beidou time synchronization module, which uses pulse-per-second (PPS) signals to achieve multi-unit synchronous sampling, and the synchronization time difference can be controlled within 100ns to ensure that the phase measurement error meets the requirements.

[0062] Signal processing module: The anti-interference circuit uses a Butterworth notch filter with a center frequency of 50Hz, which can effectively suppress power frequency interference and attenuate the power frequency signal to a low level. The amplifier circuit adopts a two-stage programmable gain amplifier structure, which can adjust the amplification factor according to the magnitude of the input signal, with a total amplification factor of up to 256 times, ensuring that weak signals can be effectively acquired and processed.

[0063] The device operates on the principle of high-precision measurement of zero-sequence impedance and mutual inductance parameters of a double-circuit transmission line under uninterrupted power conditions, through heterogeneous frequency excitation and precise synchronous acquisition technology. First, the double-circuit line simulation module uses an isolation transformer to simulate both the de-energized and energized circuits, with a 1:1 transformation ratio between the primary and secondary sides, ensuring a proportional mapping of electrical parameters on both sides. The inductive reactance of the isolation transformer is designed to correspond to the mutual impedance of the actual line, thus accurately reproducing the electromagnetic coupling characteristics between the lines under experimental conditions. The tap design at the beginning and end of the primary and secondary sides, as well as the grounding setting at the end, ensure that the simulated environment is consistent with the actual power grid operation, providing reliable equivalent conditions for measurement.

[0064] During the measurement process, the frequency-differentiated excitation module applies an AC voltage signal different from the power frequency to the simulated de-energized line (primary side), commonly at frequencies of 45Hz and 55Hz. Because the excitation frequency differs consistently from the power frequency, subsequent signal processing can effectively distinguish the excitation signal from power frequency interference components in the frequency domain. The frequency-differentiated power supply communicates with the main control unit via RS-485, allowing for dynamic adjustment of the output frequency and amplitude according to test requirements. Furthermore, the voltage can be boosted using a step-up transformer to match the impedance characteristics of lines at different voltage levels.

[0065] The power frequency effects of live lines are reproduced using a power frequency simulation module. This module applies a 50Hz power frequency supply to the secondary side of an isolation transformer after adjusting it to 220V via a voltage regulator, creating an inductive environment consistent with the actual operating line. Under these conditions, the de-energized line contains both test signals injected by the different frequency power supply and power frequency interference signals coupled in through the isolation transformer, fully simulating the complex interference background of the engineering site.

[0066] To accurately extract inter-frequency signals amidst complex interference, the synchronous acquisition module plays a crucial role. Equipped with an openable clamp-on current sensor and a high-precision voltage transformer, the module acquires current and voltage signals respectively, ensuring a linear proportional relationship across the entire measurement range. The BeiDou time synchronization module utilizes pulse-per-second (PPS) signals to achieve nanosecond-level synchronization (time difference less than 100ns) between multiple acquisition units, fundamentally reducing phase errors and ensuring impedance measurement accuracy meets engineering requirements of less than 1%.

[0067] Finally, the signal processing module performs anti-interference and amplitude optimization on the acquired signals. First, a Butterworth notch filter deeply attenuates the 50Hz power frequency component, retaining only the frequency components of the heterodyne excitation, thus reducing the impact of power frequency interference on the measurement results at the source. Subsequently, a two-stage programmable gain amplifier circuit automatically adjusts the gain according to the input signal amplitude, achieving a total amplification factor of up to 256 times, enabling the clear acquisition of weak voltage and current signals. After the above processing, the output data can be directly used for accurate calculation of zero-sequence impedance and mutual inductance parameters, realizing safe, reliable, and high-precision line parameter measurement under uninterrupted power conditions.

[0068] This invention provides a live-line testing method for the zero-sequence impedance parameter of a mutual inductance line, comprising the following steps:

[0069] Line simulation and wiring: Connect the first tap of the primary side of the isolation transformer to a different frequency power supply, and ground the last tap, as the de-energized line; connect the first tap of the secondary side to a power frequency power supply, and ground the last tap through a current-limiting resistor, as the energized line. Deploy current sensors and voltage sensors at the beginning and end of the de-energized line, the beginning and end of the energized line, respectively, to collect the corresponding current and voltage signals.

[0070] Synchronization and Time Alignment: The BeiDou time synchronization module of each measurement unit is activated to receive BeiDou satellite signals. The time of each measurement unit is synchronized through the pulse-per-second (PPS) signal to ensure that the sampling time error of each measurement unit is less than 100ns, providing an accurate time reference for synchronous signal acquisition.

[0071] Inter-frequency signal acquisition: The inter-frequency power supply sequentially outputs 45Hz and 55Hz inter-frequency voltage signals, and different voltage levels (such as 100V, 200V, 300V, 500V, etc.) can be selected according to testing requirements. At each frequency and voltage level, the synchronous measurement unit records... .

[0072] Parameter calculation: Based on the acquired heterogeneous frequency signals,

[0073] Calculate the self-impedance of the power outage line : ;

[0074] Calculate the mutual impedance of the two circuits. : .

[0075] Then, using the frequency conversion formula ( For different frequency impedances, (45Hz or 55Hz), converting the different frequency parameters to power frequency parameters.

[0076] Error verification: The measured power frequency parameters (self-impedance) are used for verification. ), mutual impedance ( Compare the values ​​with the preset simulation or design values ​​to calculate the impedance error and phase error, ensuring that the impedance error is less than 1% and the phase error is within ±0.2°. If the error does not meet the requirements, analyze the cause and adjust the test parameters or device settings, and repeat the test.

[0077] Specifically as follows:

[0078] S1. Connect a grounded power supply (frequency 45Hz and 55Hz) to primary tap 1 of the isolation transformer. Primary tap 2 of the isolation transformer is directly grounded. Use voltage transfer unit 1 to measure the voltage at primary tap 1. ), use current unit 1 to measure the current of primary tap 1 ( ).

[0079] S2. Connect a 50Hz power supply with one end grounded to tap 1 on the secondary side of the isolation transformer. Tap 2 on the secondary side of the isolation transformer is grounded through current-limiting resistor R1. Use voltage unit 2 to measure the voltage at tap 1 on the secondary side. ), use current unit 2 to measure the current of secondary tap 1 ( ); Use voltage unit 3 to measure the voltage of secondary tap 2 ( ).

[0080] S3, the power frequency power supply output voltage is set to 220V, simulating the operation of transmission line 2;

[0081] S4. The output voltage of the AC power supply at 45Hz and 55Hz is set to 100V. Start measuring and recording the readings of each meter. Calculate the zero-sequence impedance of transmission line 1, the zero-sequence impedance of transmission line 2, and the mutual inductance impedance between transmission line 1 and transmission line 2 at 45Hz and 55Hz. Then convert the results to 50Hz.

[0082] S5. Compare the experimental results with the simulation data and analyze and verify the results.

[0083] As shown in Table 1, the experimental results were recorded, and the voltage-current phase difference was found to be 56.12.

[0084] Table 1

[0085]

[0086] The data processing procedure is as follows:

[0087] ;

[0088] ;

[0089] ;

[0090] .

[0091] I. Specific application areas or related products of this invention.

[0092] Power Grid Operation and Maintenance: In the daily operation and maintenance of the power grid, it is necessary to regularly measure and evaluate the parameters of transmission lines. This invention can accurately measure the zero-sequence impedance and mutual inductance parameters of double-circuit transmission lines without interrupting power supply, providing important data for the stable operation of the power grid. For example, when detecting aging or potential faults in lines, precise measurement of parameter changes can promptly identify potential problems, allow for advance planning of maintenance schedules, and reduce the occurrence of power outages.

[0093] II. Evidence related to the technical effects obtained by the embodiments of the present invention.

[0094] In 2023, a pilot application was conducted on an actual line at a substation in China. A double-circuit 110kV transmission line was selected, with one circuit energized and the other de-energized for maintenance. The device and method of this invention were used to measure zero-sequence impedance and mutual inductance parameters. The measurement results were compared and analyzed with the line design values ​​and historical measurement data. The results show that the measurement results of this invention deviate from the design values ​​by 1.3%, and show good consistency with historical measurement data, verifying the accuracy and reliability of this invention.

[0095] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A live-line testing device for zero-sequence impedance parameters of mutually inducted circuits, comprising: A double-circuit line simulation module is used to construct a simulated double-circuit transmission line. The double-circuit line simulation module includes an isolation transformer. The primary side of the isolation transformer corresponds to the de-energized line, and the secondary side corresponds to the energized line. Taps are set at the beginning and end of the primary and secondary sides, and the end tap is grounded. A frequency-dependent excitation module is used to apply a frequency-dependent voltage signal to the power outage line. The frequency-dependent excitation module includes a frequency-dependent power supply, which outputs sinusoidal voltages with frequencies of 45Hz and 55Hz. The power frequency analog module includes a power frequency power supply and a voltage regulator. The power frequency power supply is used to apply a power frequency voltage signal to the live line. The synchronous acquisition module is used to synchronously acquire the voltage and current signals of the de-energized and energized lines, and includes at least three synchronous current and voltage measurement units, each equipped with a current sensor, a voltage sensor, and a BeiDou time synchronization module. The signal processing module includes an anti-interference circuit and an amplification circuit. The anti-interference circuit is used to suppress power frequency interference, and the amplification circuit is used to amplify the acquired signal.

2. The apparatus as claimed in claim 1, characterized in that, The inductive reactance values ​​of the primary and secondary sides of the isolation transformer correspond to the inter-line mutual impedance Z12, and the turns ratio of the primary side to the secondary side is 1:

1.

3. A live-line testing method based on the zero-sequence impedance parameter of the mutual inductance line according to the device as described in claim 1 or 2, comprising the following steps: S1. Line simulation and wiring: The primary side of the isolation transformer is used as the de-energized line, with the first end connected to the variable frequency power supply and the end grounded; the secondary side is used as the energized line, with the first end connected to the power frequency power supply and the end grounded through the current limiting resistor. S2. Time synchronization: The BeiDou time synchronization module is used to synchronize the time of each measurement unit. S3. Different frequency signal acquisition: Apply 45Hz and 55Hz different frequency voltage signals to the power outage line in sequence through the different frequency power supply, and simultaneously acquire the voltage and current signals at the beginning and end of the power outage line as well as the voltage and current signals at the beginning and end of the energized line. S4. Parameter calculation: Calculate the self-impedance of the outage line and the mutual impedance of the two circuits based on the collected heterogeneous frequency signals, and convert the heterogeneous frequency parameters into power frequency parameters. S5. Error verification: Compare the measured parameters with the preset parameters to verify the measurement error.

4. The method as described in claim 3, characterized in that, The frequency conversion formula is as follows: ， Where Zf is the power frequency impedance, Zx is the different frequency impedance, fx is 45Hz or 55Hz, and f is 50Hz.

5. A signal processing module for live testing of zero-sequence impedance parameters of mutually inducted lines, comprising: Butterworth notch filter, with a center frequency of 50Hz and an attenuation of 40dB or more, is used to suppress power frequency interference. A two-stage programmable gain amplifier circuit with a total amplification factor of less than or equal to 256 times is used to amplify the acquired signal.

6. The signal processing module as described in claim 5, characterized in that, The two-stage programmable gain amplifier circuit is designed according to the pattern of coarse amplification in the front stage and fine amplification in the back stage, and automatically adjusts the gain according to the amplitude of the input signal.

7. A synchronous acquisition module for live testing of zero-sequence impedance parameters of mutually inducted lines, comprising: An openable clamp-on current sensor is used to collect current signals from the secondary side of a current transformer. High-precision voltage transformers are used to acquire line voltage signals; The BeiDou timing module uses second pulse signals to achieve multi-unit synchronous sampling with a synchronization time difference of less than 100ns.

8. The synchronous acquisition module as described in claim 7, characterized in that, The current sensor has a range of 0 to 30A, and the voltage transformer has an accuracy class of 0.

01.

9. A double-circuit line simulation module, comprising an isolation transformer, wherein the inductive reactance values ​​of the primary and secondary sides of the isolation transformer correspond to the inter-line mutual impedance Z12, the transformation ratio of the primary and secondary sides is 1:1, the primary side simulates a de-energized line, the secondary side simulates a energized line, and taps are respectively provided at the beginning and end of the primary and secondary sides, with the end tap grounded.

10. The dual-circuit line simulation module as described in claim 9, characterized in that, The end taps of the primary and secondary sides are connected to the ground grid through grounding protection devices to improve operational safety during live testing.

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