Case Studies-Health Monitoring of Power Transmission Equipment Using Insulating Oil Analytical Methods

This paper presents cases which are encountered during routine monitoring of oil DGA for the 400 kV class and 765 kV class equipments (transformers and reactors). Fault detection of the four equipments was conducted based the DGA and equipment were then subjected to preventive actions.

Using Dissolved Gas Analysis excess values of C₂H₂ gas were reported for 1st case and preventive actions were taken. The equipment is being monitored further. In 2nd case, a rapid rise in H₂ gas content was observed and the improper processing during the past oil filling activity were then ractified. In 3rd case the equipment suddenly tripped with loud sound and the existence of high energy electrical fault were evident in DGA as well as site inspection. Fault had happened because of gradual weakening of phase – phase insulation inside the main tank up to approximately 45 kA of fault current. In the 4th case, Duval Pentagon Analysis showed the system continuously in thermal fault zone Upon inspection severe damages were observed in lead insulation, copper of neutral lead, wooden turret CT supports and neutral turret CT insulation. For the 5th case high energy discharge observed in DGA was confirmed with diverter switch inspection.