Preventive maintenance system with a different gas injecting facility for GIS

A preventive maintenance system for gas insulated switchgear (GIS) is developed. It detects signs of trouble and prevents breakdowns in service. The system constantly monitors UHF signals, which are generated by partial discharges (PDs), and propagate in the GIS, by using couplers built into the apparatus. The PDs are detected at high sensitivity (5 pC) and located according to the attenuation of the signals. Then the system injects a different gas into the section where PDs are occurring and improves the dielectric strength. This prevents faults in service and allows remedial actions to be taken with less accuracy. By injecting a small quantity (5-10%) of c-C/sub 4/F/sub 8/ into the GIS, dielectric strength is raised more than 20%. A preventive maintenance system with a facility to inject a different gas is constructed for a full-scale GIS model. The system detects and locates PDs, and automatically injects the different gas to improve the dielectric strength.<>