Forewarning Of Oil-Impregnated Insulation Faults to Ensure Staff Safety

Substation equipment failure can have catastrophic effects on the power system as well as produce localised damage within the substation switchyards. Moreover, the safety of personnel can be put at great risk. In 2004, a major system incident occurred following the explosive failure of a current transformer in a transmission substation. This event resulted in the loss of generating capacity and load. Condition monitoring equipment installed in this substation failed to identify any problems associated with the current transformer prior to the event. However, a separate data recording facility installed on the current transformer secondary circuitry observed a series of current pulse trains prior to the explosion. It is proposed that these are due to the insulation degradation within the transformer. Given these observations, ten minutes of forewarning could have been provided for the event. This paper describes the design and testing procedure for a condition monitoring system used to identify similar incidents in oil/paper insulated current transformers