On-line monitoring unit for leakage current of zinc oxide arrester

Abstract

An on-line monitoring unit for leakage current of a zinc oxide arrester comprises a zinc oxide valve block, a rectification circuit, a current mutual inductor, a sampling resistor, a signal conditioning circuit and a CC2430 chip, wherein the original edge coil of the current mutual inductor is serially connected between the rectification circuit and ground; the secondary edge coil is connected tothe sampling resistor in parallel; the voltage input end of the signal conditioning circuit is connected to two ends of the sampling resistor; the signal output end of the signal conditioning circuitis connected to the difference sampling signal input end of the CC2430 chip. The inventor has the courage to break through the traditional prejudice, and daringly connects the original edge of a precise current mutual inductor between the rectification circuit and ground directly and serially; the current mutual inductor can measure a weak leakage current less than 0.02mA; the precision reaches 0.2 level, and the electric signal is strong; the precision requirements to the following filter amplifying circuit are reduced; the phase of the output signal of the filter amplifying circuit and the phase of the original edge current are ensured to be the same; the calculation accuracy of the resistive currents is improved; the current mutual inductor is not destroyed by high voltage; and unexpected effect is obtained.

Description

technical field [0001] The invention relates to an on-line monitoring unit for leakage current of a zinc oxide arrester. Background technique [0002] The leakage current of the arrester in the substation is an important characteristic quantity to judge the operation state of the arrester. The arrester on-line monitoring system needs to sample the leakage current in order to obtain the resistive and capacitive components of the leakage current. [0003] The leakage current sampling methods in the general surge arrester online monitoring system mainly include the following types: [0004] (1) Small voltage signal method. This method is to obtain a small voltage signal at both ends of the leakage counter, and then divide it by the resistance of the counter to obtain a full current signal. Using this method must require the voltage signal at both ends of the counter to be in a linear relationship with the current signal flowing through the counter, so as to ensure the correc...

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Problems solved by technology

However, the leakage current of the arrester is generally very small (mostly lower than 5mA), which makes the production of the sensor very difficult. The follow-up circuit needs to add a more precise filter and amplifier circuit. The output signal of the filter and amplifier circuit is no longer in phase with the primary current. The calculation of the resistive current brings a large error, and even loses the possibility of calculating the resistive current

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