A new fault location technique for three-terminal transmission grids using unsynchronized sampling

Abstract

This paper presents a three-terminal fault location algorithm based on the unsynchronized voltage and current phasors acquired from the digital relays or the Intelligent Electronic Devices (IEDs) installed in three terminals. The idea is to extend a two-terminal fault location scheme using synchrophasors to an approach regarding the three-terminal line structure with unsynchronized sampling. Firstly, a Voltage Comparison Scheme (VCS) is proposed to simultaneously identify a faulted line branch and derive the synchronization angle between the ends of the remaining two healthy branches. Subsequently, the Modified Secant-based Algorithm (MSA) is suggested to synchronize the measurements of the faulted-branch end as well as locate a fault at the same time. The effectiveness and the performance of the proposed idea have been validated by an extensive series of simulations under various fault conditions with the use of the 161 kV overhead transmission-line parameters of the Taiwan Power Company (Taipower).