IMPROVING DISTANCE RELAY PERFORMANCE FOR STATCOM- COMPENSATED TRANSMISSION LINES

Abstract

This thesis proposes a new technique for estimating an accurate apparent impedance in systems equipped with STATCOM device at its midpoint. The main goal of this thesis is to eliminate the impacts of both the shunt current of the STATCOM device and the fault resistance on apparent impedance calculation in order to obtain accurate fault distance. The technique depends on synchronizing phasors measurement units (SPMUs) to transmitted data from the midpoint connection and from the receiving end to the relay at sending end. The fault resistance is mathematically calculated based on active power values at sending and receiving ends. Unlike the published methods, which are valid only if the fault resistance is much larger than the TL resistance, the proposed method is valid whatever the value of fault resistance compared to the TL resistance. Moreover, the proposed method is valid for both ground and phase faults. The proposed algorithm is extensively investigated on part of a 400 kV, 50 Hz power grid consists two series transmission lines with three generating sources. The STATCOM FACTS device is assumed to be connected at midpoint of line. The achieved results ensure the effectiveness of the proposed method.