| Metal Oxide Arrester (MOA) consists of nonlinear resistance cards, it has excellent nonlinear current-voltage characteristic. As an important over-voltage protection device, it is widely used in power system. MOA chronically works under an open-air atmosphere in high voltage line, so it will easily cause failure and malfunction. This will seriously threat to other electrical equipment's safety running. So the regularly inspection and maintenance on MOA is indispensable. Judging the performance of MOA is mainly for the analysis of its resistance current from the leakage currents. The key to the detection is to isolate the faint resistance current from the leakage currents. However, due to the interference of surrounding other electric equipment, the current and voltage signal is distorted, there is an error resides in the analysis and calculation of resistance current. So it needs to design a simple and reliable testing equipment in practical applications.This paper analyses the working principle and functional characteristic of MOA. According to its simplified equivalent circuit, the actual methods including the total current method, resistance current third harmonic method, conventional compensation method, measurement based on the temperature method and harmonic analysis method are researched and compared. As the needs of the enterprises, certain technical requirements and specifications, this paper designs a MOA tester, using dsPIC30F6015 as its control core. The hardware of system includes LCD module, voltage signal acquisition circuit, leakage current measurement circuit, frequency measurement circuit, keyboard interface circuit and printer interface circuit. According to the design of each module, C language is used to program the software.After testing in the company, the MOA tester designed in this paper is stable and reliable. Its basic performance meets the requirements. Now it is being designed based on the standard of productization (industrialization) for trail. |
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