Partial Discharge Monitoring as a Diagnostic Tool for Pollution Severity Assessment of 220 kV Power Transmission Line Insulators

This paper presents a practical application of a technique for outdoor electric power transmission line insulator pollution assessment based on partial discharge detection and analysis. Data from PD monitoring systems installed on two 220 kV transmission line towers in proximity of a coastal region in Italy are reported in this paper. Tower-A was equipped with Room Temperature Vulcanized (RTV) silicone rubber coated glass insulators and Tower-B with uncoated insulators. The investigation serves the purpose of collecting typical partial discharge patterns from line insulators in order to verify a technique to infer insulator pollution level. PD activity was continuously monitored on towers A and B from November 2007 to May 2008. It is observed that PD on insulator B is much stronger than PD on insulator A. These results support the effectiveness of partial discharge detection and analysis as a tool to carry out condition-based maintenance of insulators of overhead lines. In particular, it is observed that partial discharge analysis highlights the mechanisms bringing insulators to flashover (dry band arc activity) and is, therefore, well suited to predict increasing pollution and imminent flashover.