Three-Phase Symmetrical Fault Detection during Load encroachment based on Superimposed Component Complex Power to Support Correct Operation of Zone 3 Distance Relays

Inappropriate operation of zone 3 distance relays in transmission network during power system stressed condition such as load encroachment situation have reported as an important factor contributing in triggering the cascading outages. Symmetrical events such as power swing, power flow transfer resulted from line outage and voltage instability can threaten the security of protection system and cause the malopertion of zone 3 distance relay. Another challenge is the fast and dependable distinguishing the three phase faults during the load encroachment condition.  In this paper, a supervisory index is presented based on phase angle of superimposed component complex power which is extracted from synchrophasor measurements obtained from both ends of lines covered by zone 3 distance relay. The proposed index has the proficiency in fast detection of three phase faults from load encroachment in less than one cycle. Unaffected by high fault resistance, fault location,fault inception angle and series compensation capacitor are the outstanding features of the proposed index. The validity of the proposed scheme is confirmed on 39-bus New England test system.