| Outdoor insulation represents an important component of electric power transmission and distribution systems considering that a single insulator failure can result to an excessive outage of the power system. Different insulator designs and materials are employed by power corporations and their behavior is investigated and tested in lab and field tests as well as during service conditions. Specimens (rods and plates) are also tested when researchers focus on investigating certain phenomena of surface activity or materials' performance without being influenced by the insulator design. The performance of insulators is strongly linked with local conditions especially related to the accumulation of pollutants and the wetting mechanisms present. Leakage current is a well established tool to monitor and investigate surface electrical activity, which is strongly correlated to surface and material condition, experienced pollution and local conditions, and, thus, the overall performance of insulators. The scope of this paper is to review leakage current monitoring conducted by different researchers worldwide in respect to the variety of applications, the waveform shapes recorded, the correlation of waveform shapes and surface activity, the techniques applied on leakage current waveforms, the extracted and measured values, the derived conclusions and overall significance of leakage current as a monitoring and investigating tool. |
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