A novel overcurrent relay with universal characteristics

In this paper, a novel overcurrent relay with universal characteristics is proposed. The relay can be uniquely coordinated with electromechanical, static and other numerical relay versions in a flexible pattern. Two electromechanical relays are experimentally tested and the curves are efficiently modeled. The modeled curves are implemented along with the IEC overcurrent curve equations. A DSP board interfaced with a multi input/output board is employed to examine the real time operation of the proposed relay algorithm. The relay hardware is tested according to the newly recommended IEEE standards. Computer simulation tests are used to measure the relay dynamic performances. The critical issues of the dynamic tests are emphasized. The test results have proven the superior performance of the proposed relay, particularly when being coordinated with other relay technologies