Power distribution problems on 11 kV feeder networks in Akure, Nigeria

This paper presents an investigative study on a selected 11 kV distribution feeder network in Akure township, Nigeria. The study was aimed at evaluating power distribution problems and solution proposals for effective application of existing 11 kV feeders for power supply within Nigeria. Time series load data on the sample feeder were analyzed to evaluate feeder failure rates, mean down times per outage, and availability. The network was surveyed to produce a map and circuit diagrams of spatial relationships of its elements. Loading and voltage profiles of the network were evaluated using direct measurements at 63 distribution transformers and computation of loading coefficient and currents. Solutions were proposed and tested computationally with consideration of 10 year future load estimate. Problems established include: low network availability, predominantly due to load shedding and short circuit faults; and inadmissibly poor voltage profile due to substandard source-end voltage. It was established that mitigating these problems require standard routine and planned maintenance practice and quick repair response to minimize failure rate and mean downtime: if network availability of 0.9 is acceptable, then a minimal failure rate of 1 event/week must be cleared under 24 hours; at a desired 0.999 availability, at failure rate of 1 to 6 events per year, the outage clearance would range from 9 to 1 hour. Furthermore, the Power Company must provide standard input voltage (1.05-11kV) to the network in order to normalize end-users voltage quality.