Research On On-line Monitoring Equipment Of Metal Oxide Surge Arrester Based On DSP

Metal Oxide Surge Arrester (MOA) is an important over-voltage protective equipment of power system. It is very important for the power system to know its operating state timely and accurately through on-line monitoring.Firstly, the current commonly used on-line monitoring methods of MOA and several interfering factors are analyzed in the thesis. According to the operating characteristics of MOA, the harmonic current generated by the harmonic voltage is obtained with a linear equivalent resistance. According to the relationship between phases's voltage and current, the current composition in the whole current and interfering status of phases, the extraction algorithm of the fundamental and the third resistive current is proposed. The simulation shows that the algorithm effectively reduces the error generated by the harmonic voltage and phase interfering.Secondly,fuzzy theory is used to analyse the MOA's faults. According to the common faults in the course of the operation of MOA and the fuzzy relationship between the faults and the fault symptoms, the faults set, fault symptoms set, membership function, fuzzy diagnosis matrix, fuzzy operator and diagnosis rules are determined.Thirdly, a type of low current sensor which can track the variation of magnetizing current and compensate it by active electronic circuit to assure the magnetic core working in"zero flux"condition is developed. Its working principle, compensation electronic circuits, structure and shielding are analyzed and the performance test shows that the compensation gets satisfactory result.Lastly, the hardware of the MOA's online monitor is designed with TMS320F2812 and it includes the signal conditioning circuit, DSP minimum system and RS485 communication module. The corresponding software program, which includes A/D sampling subprogram, data-processing subprogram and communication subprogram, is designed. The MOA's online monitor management system, which can achieve data display, storage, query and fault diagnosis, is designed with C#2.0 too.