Online Monitoring System for Lightning Arrester Leakage Current and Calculation Method for Resistive Leakage Current

Abstract

The present invention relates to an on-line monitoring system for the leakage current of a lightning arrester and a method for calculating the resistive leakage current. By using the fast Fourier transform algorithm, the fundamental component and the high-order harmonic components of the leakage current of the lightning arrester, as well as the fundamental component and the high-order harmonic components of the system voltage where the lightning arrester is located, are obtained; the fundamental component and the high-order harmonic components of the leakage current are respectively orthogonally decomposed into capacitive components and resistive components, where the capacitive component leads the voltage component of the same frequency by a quarter of a cycle; the fundamental component and the high-order harmonic components of the capacitive current are subtracted from the leakage current to obtain the resistive component of the leakage current; through the cooperation of the signal acquisition device and the information processing device and after calculation, the waveform of the resistive current component of the leakage current of the lightning arrester is obtained, meeting the requirements of on-line monitoring of the leakage current of the lightning arrester. It can timely detect the defects of the lightning arrester and is of great significance for ensuring the safe and stable operation of the power system.

Description

Technical Field

[0001] The present invention relates to an on-line monitoring system for the leakage current of a lightning arrester and a method for calculating the resistive leakage current, belonging to the technical field of on-line monitoring systems. Background Art

[0002] The zinc oxide lightning arrester is an important device to ensure the reliable operation of the power system. However, defects such as poor structure, loose sealing, and aging of the valve plate can cause an increase in its resistive leakage current, which in turn leads to damage or explosion of the lightning arrester, seriously threatening the safe operation of the power system. On-line monitoring of the leakage current of the lightning arrester can timely detect the defects of the lightning arrester, which is of great significance for ensuring the safe and stable operation of the power system.

[0003] The leakage current of the zinc oxide lightning arrester includes a capacitive component and a resistive component, where the resistive component only accounts for 5%-20% of the total leakage current. Although its content is small, it is a key indicator reflecting the health status of the lightning arrester. Therefore, accurately measuring the resistive component of the leakage current of the lightning arrester is the key to timely detecting the defects of the lightning arrester. Currently, the commonly used on-line monitoring methods for lightning arresters include the full-current method, the fundamental wave method, the third-harmonic method, the capacitive current compensation method, and the harmonic analysis method, etc.

[0004] The full-current method measures the full current flowing through the lightning arrester by connecting an AC ammeter in series with the grounding end of the lightning arrester. Since the resistive current reflecting the health status of the lightning arrester accounts for a relatively low proportion of the full current, the monitoring result of this method is difficult to accurately reflect the state of the lightning arrester.

[0005] The fundamental wave method obtains the amplitudes and phases of the full current and the system voltage through fast Fourier transform, and then calculates the fundamental wave component of the resistive current in the full current through the phase difference between the two fundamental waves. This method only considers the fundamental wave component of the resistive current and does not consider the harmonic components, and cannot comprehensively reflect the health status of the lightning arrester.

[0006] The third-harmonic method monitors the sum of the three-phase leakage currents. When the three phases are balanced, the sum of the fundamental wave currents is zero, and the obtained result is the sum of the three-phase harmonic components, mainly the third harmonic. The accuracy of this method is affected by factors such as inter-phase coupling and voltage harmonics, and it cannot indicate the magnitude of the resistive current of each phase separately.

[0007] The capacitive current compensation method provides a reverse capacitive current through an external compensation circuit, and by continuously adjusting the magnitude of the compensation current, the capacitive current component is offset to obtain the resistive current component. The accuracy of this method is affected by factors such as inter-phase coupling, voltage harmonics, and phase shift during signal measurement.

[0008] The harmonic analysis method digitizes the voltage signal and the total current signal, and then through the fast Fourier transform, the fundamental wave and the harmonic signals of the two signals are obtained. The harmonic analysis method can simultaneously measure and analyze multiple characteristic quantities for monitoring the operating state of zinc oxide arresters, and is less affected by system harmonics, and can more accurately reflect the operating state of zinc oxide arresters. The accuracy of voltage and current phase sampling is the main factor affecting the calculation accuracy of the harmonic analysis method.

[0009] Therefore, there is a need for a method to accurately measure the resistive component in the leakage current of the arrester, realize on-line monitoring of the operating state of the arrester, and ensure the safe operation of the power system. Summary of the Invention

[0010] The purpose of the present invention is to provide an on-line monitoring system for the leakage current of an arrester and a method for evaluating the health status, so as to solve the problems raised in the above background technology.

[0011] The technical solution of the present invention is as follows:

[0012] A method for calculating the resistive leakage current of an arrester includes the following steps:

[0013] Obtain the fundamental wave component and high-order harmonic components of the arrester leakage current, and the fundamental wave component and high-order harmonic components of the voltage of the system where the arrester is located through the fast Fourier transform algorithm;

[0014] Orthogonally decompose the fundamental wave component and high-order harmonic components of the leakage current into capacitive components and resistive components respectively, where the capacitive component leads the voltage component of the same frequency by a quarter of a cycle;

[0015] Subtract the fundamental wave component and high-order harmonic components of the capacitive current from the leakage current to obtain the resistive component of the leakage current.

[0016] An on-line monitoring system for the leakage current of an arrester includes:

[0017] A signal acquisition device for signal sensing, signal amplification, signal conversion and signal transmission;

[0018] An information processing device for signal reception, information processing, information display and information storage;

[0019] The information processing device is communicatively connected to more than one group of the signal acquisition devices.

[0020] Preferably, the signal acquisition device includes:

[0021] A signal sensing module for obtaining the voltage signal of the system where the arrester is located and / or the leakage current signal of the arrester;

[0022] A signal amplification module for amplifying the signal;

[0023] A signal conversion module for converting an analog signal into a digital signal;

[0024] A first communication module for transmitting signals;

[0025] A first data processing module for coordinating the work of each module of the signal acquisition device and processing data;

[0026] A satellite time service clock module for providing a time reference.

[0027] Preferably, the information processing device includes:

[0028] A second communication module for transmitting signals;

[0029] A second data processing module for coordinating the work of each module of the information processing device and processing data;

[0030] A human-machine interface module for human-machine information exchange;

[0031] A storage module for storing information;

[0032] The first communication module and the second communication module are communicatively connected.

[0033] Preferably, both the signal acquisition device and the information processing device include a power supply module for supplying power to each of them.

[0034] Preferably, multiple signal acquisition devices collect voltage and current signals at the same moment according to the clock signal provided by the satellite time service clock module.

[0035] Preferably, the information processing device is used to calculate and display the waveforms of the capacitive fundamental component, capacitive harmonic component, resistive fundamental component, and resistive harmonic component of the arrester leakage current.

[0036] Preferably, the communication connection is a wired communication connection or a wireless communication connection.

[0037] Preferably, the information processing device is used to record and display the curves of the leakage current components changing with time.

[0038] Preferably, the information processing device is used to calculate the calculation error of the voltage-current phase difference when the voltage signal does not contain harmonic components, record it, and use it as the error correction basis for subsequent voltage-current phase difference calculations; a method for eliminating the voltage-current phase measurement error is pointed out.

[0039] The present invention has the following beneficial effects:

[0040] Through the cooperation of the signal acquisition device and the information processing device, and through calculation, the resistive current component waveform of the arrester leakage current is obtained.

[0041] An on-line monitoring system for arrester leakage current and a calculation method for resistive leakage current that can accurately calculate the resistive leakage current of the arrester are provided, meeting the requirements of on-line monitoring of arrester leakage current. It can promptly detect the defects of the arrester, which is of great significance for ensuring the safe and stable operation of the power system. Brief Description of the Drawings

[0042] Figure 1 It is the schematic diagram of the on-line monitoring system for arrester leakage current in the present invention;

[0043] Figure 2 It is the schematic diagram of the system structure of the present invention. Detailed Embodiments

[0044] The present invention will be described in detail below in conjunction with the drawings and specific embodiments.

[0045] Embodiment:

[0046] As Figure 1-2 shown:

[0047] The signal sensing module (current transformer / voltage transformer) and the signal amplification module (amplifier) constitute a current-voltage conversion circuit to measure the arrester leakage current and voltage and perform corresponding signal amplification. The signal conversion module converts the amplified analog signal into a digital signal. The first data processing module receives the digital signal and sends the digital signal to the second data processing module through the communication cooperation of the first communication module and the second communication module;

[0048] The second data processing module analyzes and calculates the digital signal, and displays the capacitive fundamental wave component waveform, capacitive harmonic component waveform, resistive fundamental wave component, and resistive harmonic component waveform of the arrester leakage current through the human-machine interface module. At the same time, when the voltage signal does not contain harmonic components, the calculation error of the voltage-current phase relationship is calculated and recorded as the error correction basis for subsequent voltage-current phase relationship calculations; the storage module saves various data for later call.

[0049] According to the clock signal provided by the satellite time synchronization clock module, the signal sensing modules of multiple signal acquisition devices collect voltage and current signals at different positions at the same time.

[0050] The second data processing module first obtains the fundamental component and high-order harmonic components of the arrester leakage current, and the fundamental component and high-order harmonic components of the system voltage where the arrester is located through the fast Fourier transform algorithm; secondly, the fundamental component and high-order harmonic components of the leakage current are respectively orthogonally decomposed into capacitive components and resistive components, where the capacitive component leads the voltage component of the same frequency (the fundamental or harmonic component of the system voltage where the arrester is located) by a quarter of a cycle (the basis for separating the capacitive component and the resistive component is clarified); finally, the fundamental component and high-order harmonic components of the capacitive current are subtracted from the leakage current to obtain the resistive component of the leakage current. The health status of the arrester is judged by analyzing the resistive component.

[0051] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method for calculating the resistive leakage current of a lightning arrester, characterized in that: Including the following steps: Obtaining the fundamental component and high-order harmonic components of the arrester leakage current, and the fundamental component and high-order harmonic components of the system voltage where the arrester is located through the fast Fourier transform algorithm; Orthogonally decomposing the fundamental component and high-order harmonic components of the leakage current into capacitive components and resistive components respectively, where the capacitive component leads the voltage component of the same frequency by a quarter of a cycle; Subtracting the fundamental component and high-order harmonic components of the capacitive current from the leakage current to obtain the resistive component of the leakage current.

2. An on-line monitoring system for the leakage current of a lightning arrester using the method according to claim 1, characterized in that: Including: A signal acquisition device for signal sensing, signal amplification, signal conversion, and signal transmission; An information processing device for signal reception, information processing, information display, and information storage; The information processing device is communicatively connected to more than one group of the signal acquisition devices.

3. An on-line monitoring system for the leakage current of a lightning arrester according to claim 2, characterized in that: The signal acquisition device includes: A signal sensing module for acquiring the system voltage signal where the arrester is located and / or the arrester leakage current signal; A signal amplification module for amplifying the signal; A signal conversion module for converting the analog signal into a digital signal; A first communication module for transmitting the signal; A first data processing module for coordinating the work of each module of the signal acquisition device and processing the data; A satellite timing clock module for providing a time reference.

4. The on-line monitoring system for arrester leakage current according to claim 3, wherein: The information processing device includes: A second communication module for transmitting the signal; A second data processing module for coordinating the work of each module of the information processing device and processing the data; A human-machine interface module for human-machine information exchange; A storage module for saving information; The first communication module and the second communication module are communicatively connected.

5. An on-line monitoring system for the leakage current of a lightning arrester according to claim 3 or 4, characterized in that: Both the signal acquisition device and the information processing device include a power supply module for providing power to themselves.

6. An on-line monitoring system for lightning arrester leakage current according to claim 3 or 4, characterized in that: Multiple signal acquisition devices collect voltage and current signals at the same time according to the clock signal provided by the satellite timing clock module.

7. An on-line monitoring system for the leakage current of a lightning arrester according to claim 3 or 4, characterized in that: The information processing device is used to calculate and display the waveforms of the capacitive fundamental component, capacitive harmonic component, resistive fundamental component, and resistive harmonic component of the arrester leakage current.

8. An on-line monitoring system for arrester leakage current according to claim 3 or 4, characterized in that: The communicative connection is a wired communicative connection or a wireless communicative connection.

9. An on-line monitoring system for the leakage current of a lightning arrester according to claim 3 or 4, characterized in that: The information processing device is used to record and display the curves of the change of each component of the leakage current with time.

10. An on-line monitoring system for the leakage current of a lightning arrester according to claim 3 or 4, characterized in that: The information processing device is used to calculate the calculation error of the voltage-current phase difference when the voltage signal does not contain harmonic components, record it, and use it as the error correction basis for subsequent voltage-current phase difference calculation.

Images