Probabilistic System Availability Model and Prevailing Factors for 33kV Primary Power Distribution Feeders in Nigeria

Outage and complimentary load flow analyses of a selected 33kV primary distribution network in Ughelli Delta State, Nigeria, were carried out to depict feeder availability obtainable in the country. Outage and load flow analyses were carried out using parametric statistics and Newton-Raphson computation algorithm respectively. The results provide model distribution of monthly feeder availability, contributions of outage factors and normal load flow values. It was concluded that: monthly feeder availability represented using normal probability distribution function of; shows that overcurrent and earth faults contribute to outage duration, taking 5% to 12% of the month outage duration respectively; coupled with significant line losses and weak voltage profile. Recommendations proposed include: replacement of weak or failed elements and insulations in the systems with new and modern ones to mitigate especially earth faults in the short term; planning for immediate increase in system capacity to accommodate the power demand effectively for present and forecast periods to eliminate load shedding, overload events, and high technical losses; maintenance practice at the planning and execution stages to mitigate failure events and repair time. Keywords – fault, outage, probability, load flow, availability, distribution network