ADAPTIVE GROUND FAULT PROTECTION FOR A DISTRBUTION NETWORK

Abstract

Due to advances in the field of digital protection, more and more utilities are using microprocessor based relays for protection of power system equipment However, the protection philosophy remains the same. The present practice of protection is to analyze all the abnormal operating conditions in advance and to set the relays considering all the Contingencies. But it is not possible to identify all operating conditions in advance and to determine a set of relay settings that are optimum for all those conditions. Compromises are, therefore, made which result in the relays exhibiting poor selectivity, slow response and even failure to operate. Many researchers are now investigating the capability of microprocessor based relays to adapt to the changing state of the power system. This approach, known as adaptive protection, will allow the relay settings to be changed dynamically to suit the prevailing operating condition of the power system. The work reported in this thesis includes the investigations for setting ground overcurrent relays in a distribution system and changing the settings to adapt to the operating conditions of the system. Four software modules were developed for this purpose and were tested using a personal computer. The results reported in the thesis demonstrate that improvements in coordination of ground overcurrent relays can be achieved when the adaptive approach of protection is implemented.