| This paper analyzed the principles and major error sources of on-line MA insulation monitoring, presented implement solutions for Yongchang power plant, accomplished type choosing, installation, testing and operation analysis. Various methods of on-line MOA insulation monitoring were researched, among which Conventional Compensation Method was selected for engineering. Considering coupled disturbances between phases, Partial Capacitance Method is used to compute disturbing current under different voltage level. For influence of voltage harmonic, Multi pie Element Compensation Method, which can efficiently eliminate the capacitive harmonic components by harmonic in electrical network, made measurement of resistive current more accurate. Based on analysis of principles and errors, the paper set up systems including signal sensors, pre-placed signal processing circuit, single chip centered signal collecting system, multi-path communication network, industry controlling computer centered processing system and general implement scheme connected with MIS system. Combing with engineering implement, studied device installation, testing, disturbance rejecting measures and faults recognition that devote on the system operating safely, reliably and stably. System testing and operating data analysis showed that MOA insulation on-line monitoring system designed in this paper is with high efficiency, stable performance, complete functions, high sensitivity and accuracy.
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