Online applicable techniques to evaluate field leakage current waveforms

Abstract

Leakage current monitoring is widely employed in order to investigate electrical surface activity and overall performance of high voltage insulators. Both activity and performance are closely linked with local conditions and experienced pollution. Therefore, field measurements are necessary to acquire an exact view of experienced activity and performance. However, field noise and the size of accumulated data are issues of concern in the case of field monitoring. In this paper, 75,887 leakage current waveforms obtained through more than six years of monitoring on 18 post insulators of different material, installed at two different 150 kV substations exposed to marine and industrial pollution, are investigated in order to evaluate the noise and data size problems. Three different types of noise are identified and their impact on raw data as well as their contribution to the data size is evaluated. Three different techniques are proposed to cope with the noise and data size problems. The techniques are selected so as to be online and hardware applicable in order to be incorporated in improved leakage current monitoring systems. Each technique is evaluated individually and in combination with the others. Combined use of all three, is proposed as a prerecording stage, able of coping with both noise and data size problems.