Abstract
A new high-speed digital distance relaying algorithm which uses fast Haar transformation techniques where transformation data window is a half cycle is proposed. In this proposed algorithm, to extract pure power frequency components, a newly designed dc-offset removing digital filter using only 2 adjacent samples is applied because all orthogonal transformations are prone to producing large errors in the presence of exponentially decaying dc-offsets, unless larger data window than one cycle is employed in the execution of the transforms. The prototype digital distance relay is based on a high speed digital signal processing processor utilizing the proposed protection algorithm. In accordance with a series of tests, the relay operating time is from 3[ms] to 11[ms] after faults in a 160 [km], 154 [kV], 60 [Hz] over-head transmission line system.
