Overcurrent relay with novel characteristics for HVDC converter protection

The paper presents a digital overcurrent relay with a novel characteristic for HVDC power converter protection. The proposed relay combines a semiconductor fuse, extremely inverse, and definite time-current characteristics on one microprocessor chip. The semiconductor fuse and the extremely inverse time-current curves have been converted into equivalent look up tables to reduce the algorithm online computation burden. The algorithm is based on an integration basis to account for the variation in the fault current. The protective relay hardware consists of a data acquisition board interfaced with a digital processing board. A laboratory test set up including a three-phase power converter transformer with the necessary transducers is instilled to examine the relay performance. The test results validate the efficacy of the new relay characteristics.