Improvement of 33kv Overcurrent Protection Scheme for Effurun Transmission Substation at PTI Road, Delta State, Nigeria

摘要

The research work is initiated to investigate Effurun 3x 60MVA, 132/33kV transmission substationnetwork, because this network faced fire outbreak, power outage several times, and abnormal tripping of feederduring last couple of years. Using ETAP software as analytical tool, the network was drawn. The data for eachcomponent in the network was collected from a site visit. The simulator was ruined and different fault scenarioswere created to analyse the existing overcurrent protection schemes and different miss-coordination oroperations results were obtained as a response of protection system to the abnormal conditions. Afterstudying this network, it was noticed that one of the main reasons for fire outbreak, outage of power andabnormal tripping of protection devices is the relay setting miss-coordination caused by the use of only definiteminimum time (DMT) and grading by time overcurrent protection scheme. Inverse definite minimum time(IDMT)relay and grading by both Time current overcurrent protection scheme was chosen, and this scheme is modelledwhich starts first by coordinating three phase overcurrent elements, for different paths from furthestdownstream up to the upstream. Next the instantaneous element as a backup protection as appliedsuccessfully. The new relay setting coordination has been applied to all relays in the Effurun substation as aresult from this study. The sequence of operation is well improved and total outage of power, abnormaltripping of feeders is significantly reduced.