ABSTRACT
Transmission lines do not directly serve loads to the consumers, but there are exceptions. The largest utility substation in the state of Georgia, USA, serves a newsprint paper mill from 230 kV transmission line. The distance protection has a major advantage that the relay zone of operation is a function of impedance of protected line though fault impedance and line length play a distinct role. The line impedance is relatively independent of current and voltage magnitudes. Thus, distance relay has a fixed reach, as opposed to overcurrent relays, for which reach varies with the system changes. As faults are at much higher currents and much lower voltages, the load phasor usually falls outside the operating circles. This is not true for reactance characteristics, which are nondirectional. Load encroachment logic prevents operation of the phase distance elements under high load conditions.
