Investigation of 150 kV capacitor voltage transformer breakdown during capacitor bank switching

This paper discuss about the investigation of 150kV capacitor voltage transformer (CVT) breakdown which is occurred simultaneously after capacitor bank disconnecting process. Analysis is performed referring to the last routine maintenance and digital fault recorder (DFR) data. Based on the analysis of both data and transient simulation analysis from the model created to represent the condition during the breakdown, it can be stated that the breakdown of 150kV CVT is due to aging of dielectric material in the CVT. Dielectric material aging of this CVT lead to the reduction of insulation overvoltage withstand in which eventually the CVT is breakdown after being hit by overvoltage stress during capacitor bank switching.