Evaluation of substation bus schemes considering reliability

The substations´ bus schemes used by Taiwan usually adopted “one and a half breaker” for 345kV system, “double bus” for 69/161kV system and “single bus with tie” for 22/11kV distribution system. This is considering both of the investment costs and reliability of electricity supply. Due to expansion plan of substation and the increasing concern of power supply reliability, considering a more suitable bus scheme for the modern substation is important. Some power companies in other countries apply double bus or ring type bus schemes for their distribution systems. Therefore, the benefit and suitability of different distribution bus schemes for Taiwan is worth to further analysis and study. The main objective of this paper is to build a reliability model and evaluation approach under different bus schemes. Therefore, the impact of a variety of distribution substations and feeder bus schemes on the load-point reliability index can be evaluated through the derivation of the distribution system reliability model. Finally, reliability evaluation approach is developed to fully evaluate the feasibility of different bus schemes for substation design and provide recommendations that considering reliability issues for the future planning of Taiwan and references for other power utilities.