DISTANCE RELAY WITH LOAD ENCROACHMENT PROTECTION FOR USE WITH POWER TRANSMISSION LINES

摘要

Voltage and current on a power transmission line are first obtained, filtered and converted to digital representations. The positive sequence components of the voltage and current are determined and the impedance at the relay is then calculated from those positive sequence voltages and currents. The positive sequence impedance is converted into a magnitude and phase angle representation and then compared against a load pattern which is also represented by magnitude and phase angle representations. If the calculated impedance at the relay is within the lead impedance pattern, the distance relay is prevented, i.e, blocked, from sending an output signal to trip a circuit breaker protecting the transmission line.