A Petri-net algorithm for multiple contingencies of distribution system operation

In this paper, a Petri net (PN) algorithm combined with a new power system restoration approach is implemented for multiple distribution contingencies. This approach is performed by releasing some loads required to maintain the rest of the system in safe operation in overload cases and opening all of the switches in the out-of-service areas for fault cases, and then closing proper switches to restore the isolated areas. PN switching models and the construction of PNs for multiple contingency operation are proposed to implement the restoration algorithm. Problem solving is efficiently performed by parallel-like reasoning in the PN for all the multiple events simultaneously. Heuristic rules and evaluation functions are presented for the best first search in the PN. Multiple contingencies studied in this paper include problems of feeder fault/overload/over-unbalance and main transformer fault/overload. A practical Taiwan power (Taipower) distribution system is simulated to demonstrate the effectiveness of the proposed method. It is concluded that multiple contingencies of distribution systems can be solved by the proposed method effectively