A positive-sequence current based directional relaying approach for CCVT subsidence transient condition

Abstract

In this work, a directional relaying algorithm is proposed for transmission line to prevent relay maloperation during coupling capacitor voltage transformer (CCVT) subsidence transient. The effect of CCVT subsidence transient during single-pole-tripping condition is highlighted in this paper. The proposed method which is based on phase angle difference of post fault and prefault positive sequence current can help the directional relay to take accurate decision during erroneous CCVT secondary response. The available CCVT model in PSCAD is not able to generate significant subsidence transient in the secondary side. So, a new CCVT model is developed in EMTDC/PSCAD domain for transient response analysis and to check the relay operation. Next, the performance of different voltage and current information based directional relaying techniques have been analyzed and compared with the proposed method. The results are evaluated for different system and fault conditions. Results demonstrate the accuracy of the proposed method.