Design of a distance relay using adaptive data window filters

This paper describes the design of a distance relay that uses adaptive data window filters to provide high speed tripping. The relay uses a fault detector to detect the inception of a fault. Starting from the fault detection, the data window size is progressively increased as new fault samples become available until the window size becomes one cycle of the fundamental frequency. At each instant, a suitable filter is used for estimating voltage and current phasors. This procedure improves the transient response of the relay and allows faster convergence of the impedance estimates and, therefore, reduces the trip time. The proposed relay was tested by using fault simulations on a sample power system. Results indicate that the proposed relay design reduces the trip times. Some results are included.