ABSTRACT
In this work, “Reliability Assessment of Electric Power Distribution”: A case study of 2x15MVA, 33/11kV,Ugbowo injection substation operated by Power Holding Company of Nigeria (PHCN) Plc was investigated.The substation historical power outage data between 2003 and 2004 comprehensively documented in the daily dispatching and operational logbooks were collected. A database was then developed using Microsoft Access in order to put the data in standard electric power reliability data format for proper data management. In order to answer a research question raised in the work on whether customers are ready to pay for a reliable power, the data on the cost of self-generated power on the event of power outages between July, 2004 and August, 2005 were collected from Guinness (Nig) Plc and University of Benin, Ugbowo Central Plant between January, 2006 and October, 2006 .The data analysis was carried out using MATLAB® program and Microsoft Excel package.
Conclusively, the results of the analysis are: The reliability of FGGC Road, Ugbowo, Eguadaiken, Uselu and Guinness 33kV line feeders at the time of the investigation are 0.78984, 0.73215, 0.75915, 0.79300 and 0.82691 in 2003 respectively while the reliability of the feeders in 2004 are 0.78879, 0.69483, 0.75938, 0.78797 and 0.83326 respectively. A Customer Billing Equation (CBE) for reliability-based electric power billing system is proposed for the Nigerian electric power system. Also a per unit reliability (ASAIp.u) system to identify worst-performing feeders for decision-making on where to invest the next naira in order to improve reliability is proposed. A Reliability indices-Markov model for the distribution system is developed, the model is calibrated with 2003 data and validated with 2004 data, the errors in prediction using the model are -0.35%,-5.5%,-0.12%,-0.7% and 0.7% for FGGC Road, Ugbowo, Eguadaiken, Uselu and Guinness 33kV line feeders respectively. A major event day analysis shows that the distribution system is not subjected to stress beyond the previous year stress. This research provides performance data required by power utility management and prospective investors to make policy and business decisions. In the study of causes of failure, load shedding has the highest impact on all the feeders including the 33kV line. This shows that there is poor electric power generation, thus there is need for a genuine intervention in the electric power generation sector. Finally, it costs Guinness (Nig) Plc and PHCN PLC N9, 200 per minute and N 4, 400 per minute respectively to operate on self-generated power. Similarly, it costs the University of Benin, Ugbowo Central Plant and PHCN PLC N 350 per minute and N 99 per minute respectively to operate on self-generated power.
