Substation monitoring by acoustic emission techniques

The deterioration of oil-paper insulation in high voltage equipment is a matter of continuous concern. The degradation typically occurs under normal operating conditions although insulation failure may be accelerated under certain in-service conditions, such as switching and lightning impulses, overvoltages and moisture ingress. For this reason, only continuous monitoring can provide the necessary field data to better understand in-service insulation behaviour, particularly insulation degradation, thus preventing catastrophic damage to property and risk to human life. Based on the promising results obtained previously from an acoustic emission (AE) portable detection system an AE substation monitoring system has been developed. This has been operational in a 33 kV primary substation for eighteen months and detailed data have been collected and downloaded to a computer from a remote site on a daily basis. The analysed results have indicated that a specific cable box in the substation is a source of heavy discharge activity and a recommendation has been made to the Regional Electricity Company that a high-voltage test be carried out on the suspected switchgear for further investigation