The algorithm for directional element without dead tripping zone based on digital phase comparator

Abstract

This paper describes the algorithm for directional element without dead tripping zone. Instead of calculating phase angle between the phasors of voltage and current the algorithm uses digital phase comparator. The procedure is based on calculation of normalized average power within one semi-period of the input voltage and current signals. Before usage the samples are passed through the Fourier filter to remove high-order harmonics and/or direct component. The dead tripping zone is eliminated by introduction of a voltage delay which is used for determination of direction. In addition, special attention is paid to the problem of synchronization which appears when signal frequency deviates from the assumed value. Sensitivity of the algorithm can be easily adjusted in accordance with the parameters of the network in which a directional element is used. Performances of the method are tested by several computer-generated signals. Since the calculations used in this algorithm are based on simple mathematical operations, the high speed of operation is achieved.