Development of on-line monitoring system for the insulation condition of capacitive-type substation equipment

On-line accurate monitoring for capacitive-type equipment insulation is a difficult problem at home and abroad, in order to decrease the interference on site and to improve the measurement precision of system, an on-line monitoring system for capacitive-type equipment insulation is designed. The system adopts a tiered and distributed multi-CPU structure, which is composed of the on-site measuring and processing unit, and data management and diagnosis system in the control room of substation. The on-site measuring and processing unit is based on DSP+FPGA hardware platform. The windows and interpolation algorithm is applied to effectively reduce the influence of asynchronous sampling caused by frequency fluctuation of power system and to increase the precision. On the basis of analyzing the influential factors of on-line monitoring system, some correlative methods for this system are proposed to increase the measurement precision. Based the simulating environments test conducted in the lab, the test results are compared with those by standard dielectric M-8000 loss measurement apparatus, the absolute errors are all less than 0.1%, it is proved that measurement accuracy of this system can meet the demands of on-site monitoring.