A nonpilot phase selector based on superimposed components for protection of double circuit lines

This paper gives details of a new phase-selection scheme for simultaneous phase-ground faults on both circuits of double circuit EHV transmission lines. Fast phase selection (within half a cycle) can be achieved by using the information contained within the fault transients. The theory is presented along with results obtained through simulations using EMTP. The scheme enables single pole tripping to be employed for simultaneous faults. The proposed scheme does not require communication between the two ends of the line. Limitations due to the low bandwidth of CVTs have not caused problems and the method has shown immunity to system noise.