An adaptive cumulative sum based method for unblocking distance relays in TCSC compensated transmission lines

Abstract

Fault detection in transmission lines with thyristor controlled series compensators (TCSC) can be challenging, in particular during power swing conditions. A reliable unblocking method based on the adaptive cumulative Sum (ACUSUM) is presented in this paper. This method alleviates the limitations of conventional methods and has the capability to detect all asymmetric and symmetric faults with high accuracy and speed. The proposed method measures the negative sequence of the current signal for fault detection. Two simulation case studies consisted of the single machine and infinite bus (SMIB) and the IEEE standard 9-bus and three machine systems are simulated in PSCAD/EMTDC to evaluate the proposed method. It is shown that the non-linear behavior of TCSC will not impact the accurate performance of this method.