CN-121978385-A - Induced current vector synthesis analysis method and device for high-voltage cable grounding system

CN121978385ACN 121978385 ACN121978385 ACN 121978385ACN-121978385-A

Abstract

The invention belongs to the field of electric power, and discloses a method and a device for synthesizing and analyzing an induced current vector of a high-voltage cable grounding system, wherein the method comprises the steps of synchronously collecting grounding current signals of a three-phase metal sheath of a high-voltage cable and synthesized current signals of wire cores of each phase through a double-Rogowski coil with consistent linearity, wherein the synthesized current signals are superposition values of running current and circulating current components; the method comprises the steps of carrying out point-by-point subtraction on a composite current sampling value and a grounding current sampling value with the same phase to offset a circulation component in a composite current signal, taking an absolute value of a difference value signal, summing the absolute value, converting the summed value into a real running current value through a preset piecewise calibration curve, carrying out discrete Fourier transform on the grounding current signal and the difference value signal respectively, expressing the two signals in complex numbers under power frequency, calculating a quotient expressed by the complex numbers to obtain a phase difference between the grounding current signal and the difference value signal, and determining the system state of the high-voltage cable grounding system based on the running current value and the phase difference.

Inventors

YANG YONG
ZHU QIJIE
ZHANG TIANBO
ZHAO LIN
MA YU
CAO JUNPING
LI TE
WANG SHAOHUA
WANG BOWEN
HE JIAN
YE HAOLIANG
LIN HAOFAN

Assignees

国网浙江省电力有限公司电力科学研究院

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. The induced current vector synthesis analysis method of the high-voltage cable grounding system is characterized by comprising the following steps of: synchronously acquiring a grounding current signal of a three-phase metal sheath of a high-voltage cable and a composite current signal of each phase wire core through a double-Rogowski coil with consistent linearity, wherein the composite current signal is a superposition value of an operation current and a circulation component; after the collected current signals are converted into digital sampling values, the same-phase composite current sampling values and the grounding current sampling values are subjected to point-by-point subtraction so as to offset circulating current components in the composite current signals, and difference signals in direct proportion to running currents are extracted; taking absolute values of the difference signals and summing the absolute values, and converting the summed values into real running current values through a preset piecewise calibration curve; Performing discrete Fourier transform on the grounding current signal and the difference signal respectively, representing the grounding current signal and the difference signal by complex numbers of the two signals under power frequency, and calculating the phase difference between the grounding current signal and the difference signal by calculating the quotient of the complex numbers; a system state of the high voltage cable grounding system is determined based on the operating current value and the phase difference.
2. The method of claim 1 wherein the characteristic of consistent linearity of the gare coil causes the circulating current component to have the same scaling factor at the digital sample level.
3. The method of claim 1, wherein the converting the summed value to a true operating current value by a preset piecewise calibration curve comprises: A mapping table of known running current and difference signal summation value is established in advance, and nonlinear errors in the whole range are compensated by adopting a piecewise linear interpolation method.
4. The method of claim 1, wherein said calculating the phase difference between the ground current signal and the difference signal by calculating a quotient of a complex representation comprises: the phase difference is calculated by adopting a complex quotient method, and the calculation formula is as follows: ; Wherein, the 、 Respectively the real and imaginary parts in the complex representation of the ground current signal, 、 The real and imaginary parts of the complex representation of the difference signal, respectively, the phase difference being corrected to a range of 0-360.
5. The method of claim 1, wherein the determining a system state of the high voltage cable grounding system based on the operating current value and the phase difference comprises: calculating a ratio of a ground current to a load current based on the operating current value, and calculating a phase difference between three-phase currents based on a phase difference between the ground current signal and a difference signal; comparing the ratio with the phase difference between the three-phase currents with a preset threshold value to determine a system state judgment result, wherein the system state comprises normal, attention and abnormality.
6. The method of claim 1, wherein the circulating current component comprises an induced current component and a capacitive leakage current component, wherein the capacitive leakage current is calculated according to the following equation: ; ; Wherein I cai represents the capacitive leakage current phasor of the I-th cable of the A phase, j represents an imaginary unit, ω represents the angular frequency of alternating current, C ai represents the total capacitance between the I-th cable core of the A phase and the metal sheath, U A represents the voltage phasor of the A-phase cable core, ε r represents the relative dielectric constant of the main insulating material of the cable, ε 0 represents the vacuum dielectric constant, D c represents the diameter of the cable core, δ represents the thickness of the main insulation of the cable, and L i represents the length of the I-th cable.
7. The method according to claim 1, wherein the method further comprises: Uploading the running current value, the phase difference and the system state to a monitoring center to generate a historical trend analysis report and early warning information.
8. An induced current vector synthesis analysis device of a high-voltage cable grounding system, which is characterized by comprising: The acquisition unit synchronously acquires a grounding current signal of a three-phase metal sheath of the high-voltage cable and a composite current signal of each phase wire core through a double-Rogowski coil with consistent linearity, wherein the composite current signal is a superposition value of an operation current and a circulation component; The subtraction unit is used for carrying out point-by-point subtraction on the same-phase synthesized current sampling value and the grounding current sampling value after the collected current signal is converted into a digital sampling value so as to offset the circulation component in the synthesized current signal and extract a difference signal in direct proportion to the running current; The conversion unit is used for taking absolute values of the difference signals and summing the absolute values, and converting the summed values into real running current values through a preset piecewise calibration curve; the solving unit is used for performing discrete Fourier transform on the grounding current signal and the difference signal respectively, representing the grounding current signal and the difference signal by complex numbers of the two signals under power frequency, and calculating the quotient of the complex numbers to obtain the phase difference between the grounding current signal and the difference signal; and a determining unit that determines a system state of the high-voltage cable grounding system based on the operation current value and the phase difference.
9. An electronic device, comprising: A processor; A memory for storing processor-executable instructions; wherein the processor is configured to implement the steps of the method according to any of claims 1-7 by executing the executable instructions.
10. A computer readable storage medium having stored thereon computer instructions which, when executed by a processor, implement the steps of the method of any of claims 1-7.

Description

Induced current vector synthesis analysis method and device for high-voltage cable grounding system Technical Field The invention belongs to the field of electric power, and particularly relates to a method and a device for synthesizing and analyzing an induced current vector of a high-voltage cable grounding system. Background The high-voltage cable is an important component of the urban power grid, and the grounding mode of the metal sheath and the state of the grounding system are directly related to the current carrying capacity, the insulating service life and the operation safety of the cable. In the related art, detection of a high-voltage cable grounding system mainly relies on manual periodic inspection, the amplitude of grounding current is measured through a clamp ammeter, and whether the system has faults such as multipoint grounding, sheath breakage and the like or not is judged by combining experience. However, since the clamp ammeter is limited by linearity, the error is large when measuring small current, and the phase cannot be accurately measured, so that accurate vector analysis cannot be performed. In addition, the current flowing in the high-voltage cable metal sheath contains a superposition of an operating current (load current) and a circulating current (induced current, capacitive leakage current). The conventional method cannot effectively separate the two components, and easily results in distortion of the evaluation of the operating current. Disclosure of Invention In view of the above, the invention discloses a method and a device for synthesizing and analyzing an induced current vector of a high-voltage cable grounding system, which can solve the defects existing in the related art. In order to achieve the above purpose, the technical scheme disclosed by the invention is as follows: according to a first aspect of the present invention, a method for synthesizing and analyzing an induced current vector of a high-voltage cable grounding system is provided, including: synchronously acquiring a grounding current signal of a three-phase metal sheath of a high-voltage cable and a composite current signal of each phase wire core through a double-Rogowski coil with consistent linearity, wherein the composite current signal is a superposition value of an operation current and a circulation component; after the collected current signals are converted into digital sampling values, the same-phase composite current sampling values and the grounding current sampling values are subjected to point-by-point subtraction so as to offset circulating current components in the composite current signals, and difference signals in direct proportion to running currents are extracted; taking absolute values of the difference signals and summing the absolute values, and converting the summed values into real running current values through a preset piecewise calibration curve; Performing discrete Fourier transform on the grounding current signal and the difference signal respectively, representing the grounding current signal and the difference signal by complex numbers of the two signals under power frequency, and calculating the phase difference between the grounding current signal and the difference signal by calculating the quotient of the complex numbers; a system state of the high voltage cable grounding system is determined based on the operating current value and the phase difference. According to a second aspect of the present invention, there is provided a high voltage cable grounding system induced current vector analysis apparatus, the apparatus comprising: The acquisition unit synchronously acquires a grounding current signal of a three-phase metal sheath of the high-voltage cable and a composite current signal of each phase wire core through a double-Rogowski coil with consistent linearity, wherein the composite current signal is a superposition value of an operation current and a circulation component; The subtraction unit is used for carrying out point-by-point subtraction on the same-phase synthesized current sampling value and the grounding current sampling value after the collected current signal is converted into a digital sampling value so as to offset the circulation component in the synthesized current signal and extract a difference signal in direct proportion to the running current; The conversion unit is used for taking absolute values of the difference signals and summing the absolute values, and converting the summed values into real running current values through a preset piecewise calibration curve; the solving unit is used for performing discrete Fourier transform on the grounding current signal and the difference signal respectively, representing the grounding current signal and the difference signal by complex numbers of the two signals under power frequency, and calculating the quotient of the complex numbers to obtain the phase difference between the grounding current sig