Distribution system reliability modeling and analysis

Abstract

With the background of imposing new electricity act and the regulatory regime for electricity industry, utilities have to be concerned not only the cost of the electricity but also the quality of the supply. As the cost of electricity is embedded to the electricity tariff, cost of reliability will also be added to the tariff in near future. Hence, utilities need to have a reliability study model to enhance the reliability of power supply at optimum level. Aim of this research is to formulate methodology to calculate supply reliability to end user by component reliability. Past three years outage data of Lanka Electricity Company (LECO) had been analysed to calculate reliability of critical path components of the distribution network. Two reliability models named direct restoration method and step restoration method had been applied to calculate sustained end user reliability indices such as SAIDI and SAIFI. End user reliability indices had been calculated using the derived component reliability for the selected distribution network portion of LECO for this purpose. Finally, the results had been compared with the absolute data for the same network as a measure of model validation. The result from the direct restoration model is deviated from the recorded results. It is noted that the results calculated by step restoration model comply with the recorded data. There were instances of deviation caused due to the non conformity of step restoration Markovian model of the network portion. Considering the validation of results, it was identified that LECO distribution network reliability shall be modeled using step restoration model. It is also noted that due to the statistical nature of component reliability, the results are also statistically distributed. The requirement of utilities to incorporate reliability criteria into their planning objectives is a requirement today in view of the regulatory governance of the electricity sector. The tariff when comes cost reflective essentially needs to incorporate cost of reliability as well.