ABSTRACT
In pilot relaying, a communication circuit is used to compare the system conditions at the terminals of the line. This provides selective high-speed fault clearance. High-speed instantaneous clearance of all types of faults has many advantages. Wave deflection from a fault is relatively a new technology, for high-speed fault clearance on extra-high voltage lines. In a transfer trip scheme, the relay at each end of the line, recognizing a fault within a designated protection zone, will send a trip signal to the relay at the remote end of the line. There is a limitation of the series resistance and capacitance of the pilot wires. Extraneous voltages are of concern. These voltages arise from a rise in station ground potential by induction from power circuits, which can be reduced by properly shielding the pilot wires. The currents are vectorially compounded from two of the terminals to produce the remote current.
