Methods of Particle Control in SF6 Insulated CGIT Systems

Phase and residually connected overcurrent relays may not detect fallen conductors or high impedance faults on a distribution circuit. Increasing the ground relay sensitivity is unacceptable since false tripping may result due to normal load unbalance and blown single phase fuses. Digital fault studies using six PP&L distribution feeders were performed in order to determine the settings and restraint element for a prototype Ratio Ground Relay. A prototype device was constructed which should detect 80-85% of the fallen conductors on PP&L's distribution system. A staged faultiest and long-term monitoring of the Ratio Ground Relay on six PP&L distribution feeders is planned.