Overall Voltage Level Reliability and Economy Coordinated Analysis in Distribution Network

at present, the reliability assessment of power system are based on their respective voltage grade which have ignored the integrity and coordination of distribution network and it can’t reflect the interaction between transmission and distribution. This paper presented a method of overall voltage level coordinated expansion planning in distribution network. Considering the effect of transmission system and the main connection schemes of substation, a top-down approach about overall voltage level reliability assessment was proposed. Based on Life Cycle Cost (LCC), the assessment of reliability and economy is carried out which select the unit increment cost of average service availability index (ASAI) as the objection function. Finally, the proposed method was well applied to different improved planning in Qinghai province, and the optimum conditions is obtained which serves the long-term interests of power grid. 