New insulation diagnostic and monitoring techniques for in-service HV apparatus

Insulation condition monitoring of high-voltage instrument transformers and transformer bushings is of significant importance in maintaining a safe and reliable electricity supply system. To achieve this, there is an increasing trend to perform in-situ insulation quality measurements on this equipment. The authors describe new insulation diagnostic and monitoring techniques, developed with the Queensland Electricity Commission, for use in an in-service HV plant. The techniques enable the dielectric dissipation factor (DDF) and partial discharge (PD) level of HV insulation to be measured while an instrument transformer or bushing is in-service. Application of the DDF measurement technique to provide a continuous insulation monitor is also covered. The continuous online system is designed to ultimately allow monitoring of all bushings and current transformers within an entire situation