A development of diagnosis system employable to high voltage insulator considering leakage current

In our previous work, some key parameters related to the variation of the leakage current from the high voltage insulator has been proposed and then experimentally investigated by use of conventional current transformer. In accordance with this suggestion, the presence of the abnormal insulators could be recognized when they are suspended together with the normal ones on the string; however real time analysis on the leakage current has not been provided. In this regards, it is envisaged to develop a diagnosis system where firmware and relevant power supply together with the necessary components are built in with a view to on-line monitoring at the site. In this work, a firmware for the analysis on the leakage current through CT has been developed using DC power supplied by solar cell built on the surface of the diagnosis system. This system is named as HY-CT Block. In other precedent reports, the increase in leakage current and PDs are considered to be one of the main causes for the dry band arcs as well as flashover. Therefore, the purpose of this work is to provide a real time monitoring related to the variation of the leakage current in order to elucidate the relationship between the previously proposed key parameters and PD occurrences. And thus, experimental setup has been constructed consisting of mainly 3 parts: Fog chamber, AC power supply and leakage current analysis system. The insulators under test are classified into three different insulation states such as normal, polluted and cracked. And then tests are carried out in order to identify the insulators in abnormal state among normal insulators suspended on the same string. In this way, the degree of danger of the abnormal insulators could be evaluated avoiding frequent surveillance. Based on the results at the laboratory, it is likely that HY-CT Block could be employed on the string for the future condition-based maintenance of the insulators under service on the high voltage overhead lines. The whole system is now installed on the 765kV transmission line at the 765kV Test yard of KEPCO located in Gochang in Korea and has been put under long term test since October 2009 for its on-site applicability