Novel method for analyzing leaked current of metal oxide lightning arrester

Abstract

The invention discloses a novel method for analyzing a leaked current of a metal oxide lightning arrester, and the method comprises the steps: firstly carrying out 10-cycle windowing, meeting the IEC standard, of a discrete sampling value (shown in the description) of a power grid signal; secondly executing nonsynchronous Hanning windowing; thirdly multiplying a frequency spectrum value at a corresponding spectral line k after DFT / FFT transformation by a twiddle phase factor (shown in the description) for two times; fourthly carrying out the superposition of amplitude vectors at frequency points obtained after transformation, so as to obtain the accurate values of the frequency, amplitude and phase parameters of the lightning arrester. The method can eliminate the picket fence effect and inhibit frequency spectrum leakage during fundamental frequency nonsynchronous sampling through the superposition of amplitude vectors at frequency points obtained after twiddle factor transformation, eliminates the impact from instantaneous large disturbances, and avoids errors appearing in a conventional FFT algorithm during nonsynchronous sampling or instantaneous large disturbances.

Description

technical field [0001] The invention relates to the field of analysis of the leakage current of a lightning arrester, in particular to a new method for analyzing the leakage current of a metal oxide lightning arrester. Background technique [0002] Through the research, it is found that the change of the operating state of the arrester is reflected in the change of the two internal parameters of the full current and the resistive current flowing through the arrester, that is, the full current and the resistive current of the arrester can be used to characterize the actual operating state of the arrester. Monitoring and early warning when the arrester is running. [0003] For the analysis of the voltage and current signals in the line with connected surge arresters, it is first necessary to measure them accurately. Theoretically, the voltage signal only contains the fundamental wave signal, while the current signal also contains the 3rd, 5th and other harmonic signals other ...

AI Technical Summary

Problems solved by technology

Theoretically, the voltage signal only contains the fundamental wave signal, while the current signal also contains the 3rd, 5th and other harmonic signals other than the fundamental signal. The traditional FFT algorithm is suitable for strong signals and small interferences. Synchronous sampling at the fundamental frequency There is no theoretical error, and the results of voltage and current are more accurate

However, the following problems may occur in the voltage and current signals in the actual circuit, which will lead to the failure of the traditional FFT algorithm detection: 1) The spectrum leakage and fence effect caused by the asynchronous sampling of the fundamental frequency, because the fundamental frequency of the power grid is always fluctuating, Its maximum fluctuation range is within ±0.5Hz, and the normal fluctuation is within ±0.2Hz, but the resulting error is relatively large, and its phase error may reach more than 5°, resulting in serious errors in subsequent calculations; 2) due to the circuit There is a lightning arrester in the device, so the voltage and current signals may be subjected to high-frequency instantaneous large interference from the lightning signal, and the hardware anti-aliasing filter may not attenuate the signal completely or the frequency of the large interference is lower than the cut-off frequency of the anti-aliasing filter , the large interference at this time has a great impact on the detection of voltage and current signals

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