Metal oxide arrester resistance current extracting method and device

Abstract

The invention discloses a metal oxide arrester resistance current extracting method and a device. The method comprises steps: initial leakage current at a zero crossing point of the metal oxide arrester is firstly acquired; frequency of the leakage current at the zero crossing point is detected and determined, the frequency of the initial leakage current is delayed by a 1/4 cycle via a delaying circuit, and new leakage current is obtained; summation is carried out on the obtained new leakage current and the initial leakage current via a summer, and combined leakage current is obtained; through detecting a time corresponding to a combined wave peak value, capacitive leakage current is generated; and the capacitive current is finally subtracted from the initial leakage current via a subtracter, and the resistance current of the metal oxide arrester is obtained. The device comprises a low-pass filter, an analog to digital conversion module, a zero-crossing detector, a frequency detector, a delayer, the summer, a peak value time detector, an automatic signal generation unit and the subtracter. In the condition of not measuring the voltage signals, capacitive current is removed in the leakage current, resistance current is obtained, the purpose of aging monitoring on the MOA can be achieved, and risks of measuring high voltage can be avoided.

Description

technical field [0001] The invention relates to the technical field of electrical equipment testing, in particular to a method and device for extracting resistive current from a metal oxide arrester. Background technique [0002] Metal Oxide Lightning Arrester (abbreviation: MOA) has highly non-linear performance, so it is well applied in lightning protection work. When the circuit works normally, it presents a high impedance state without affecting the normal operation of the circuit. However, after the lightning surge voltage is generated, it immediately presents a low-impedance state, and discharges the surge voltage to the ground. A good MOA will return to a high impedance state after discharging the surge voltage. However, due to certain factors (such as high humidity, high temperature, operating overvoltage, etc.), the MOA installed in the circuit for a long time will age and lose its protective effect, and even cause power failure accidents. Therefore, it is necessa...

AI Technical Summary

Problems solved by technology

However, these algorithms need to use many devices such as current probes and voltage probes. In actual work, more manpower and material resources are required.

In addition, in some substations or their facilities, the leakage current can be measured through the current shunt, but the measurement of its voltage does have certain difficulties

On the one hand, measuring high voltage itself has certain risks, on the other hand, measuring the voltage of a single phase may be interfered by the voltage of other phases

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