Investigation Of Power System Reliability Improvement By Using Distributed Generation:case Study Of Bishoftu Distribution Substation

Abstract

Power system is divided into the subsystems of generation, transmission, and distribution facilities according to their functions. The distribution systems account for up to 90% of all customer reliability problems. Improving distribution system reliability is the key to improving customer reliability and it is the most important part of a power system, which consists of many step-down transformers, distribution feeders, and customers. Therefore, evaluation of the reliability of power distribution is highly important at the distribution system. In the context of Ethiopia, electric power interruption is becoming a day to day phenomenon. Even there are times that electric power interruption occurs several times a day, not only at the low voltage but also at the medium voltage distribution systems. Distributed Generators (DGs) are now commonly used in distribution system to reduce the power disruption in the power system network which results in a considerable reduction in the total power loss in the system, improved voltage profiles of the bus and reliability indices. Therefore, integrating distributed generation to an existing distribution system provides profit for both utility and end users. This research work shows that the reliability of Bishoftu substation II does not meet the requirements set by the regulatory body that is, Ethiopian Electric Agency (EEA). The system average interruption frequency index (SAIFI) of the substation is 179.619 interruptions per customer per year with system average interruption duration (SAIDI) of 276.585 hours per customer per year at the basecase. Based on the simulation result, the installation of DG at 0.4 kV buses of the feeders (K7, K-8, K-9 and L-3) which experience more interruptions, resulted in the improvement of SAIFI by 92.335%, SAIDI by 88.956%, and Energy not supplied (ENS) by 97.735%. The energy not supplied is reduced from 5666.367 MWh/yr to 128.327 MWh/yr and EIC is reduced from 2.92 million $/yr to 0.741 million $/yr with average revenue saving of about 2.179 million $/yr. Thus, Ethiopian Electric Utility (EEU) can increase its revenue by 74.623% for that area by reducing the energy not supplied (ENS) due to interruptions.