Abstract

• This paper is intended to find the most reliable method in distribution by using protective devices because high reliability power system is urgently needed in Myanmar. Approximately 80% load interruptions are due to breakdown in distribution system and insufficient supply. Therefore, it is important to understand the impact of the outages on the customer’s outage costs, system adequacy and security. In this research, the impacts of protective devices installation on distribution system reliability were analyzed using analytical method and evaluation techniques. Load data on the feeders were collected from Shwe Sar Yan primary distribution substation from December 2017 to December 2018 and system data were calculated on monthly basis for one year. In this research, fuses were used in every lateral line for lateral protection and it could be seen that the energy not supplied (ENS) in feeder 1 was decreased from 448.92 MWh/yr to 32.91 MWh/yr. By using fuses, total ENS were reduced from 17207.11 MWh/yr to 4451.65 MWh/yr in all feeders besides it was abated from 17207.11 MWh/yr to 4377.14 MWh/yr because of disconnecting switch and also depleted from 17207.11 MWh/yr to 4416.71 MWh/yr by 90% protection failure. In this research, reliability improvement scheme was tested as lateral protection with fuse, feeder protection with disconnecting switches and effect of protection failure rate and then the amount of total ENS were reduced too much during one year. In this research, using disconnecting switches method is the best. By studying this research, it could be chosen the most reliable method in distribution system.