Analysis of Transformer Failure Causes and Maintenance Practices at Eko Electricity Distribution Company, Lagos

This study analyses the primary causes of distribution transformer failures and evaluates existing maintenance practices at the Eko Electricity Distribution Company in Lagos State, South West Nigeria. Distribution transformer failures are a leading cause of prolonged power outages in Lagos, the most densely populated state in Nigeria, with significant consequences for residential consumers, commercial establishments, and emergency services. Data on 120 transformer failure incidents over a three-year period were obtained from EKEDC's fault management database and supplemented by structured interviews with 25 maintenance engineers and field technicians. Failure causes were categorised and analysed using a Pareto chart approach. Results indicate that oil deterioration and insulation failure together account for 54 percent of all failures, followed by overloading at 21 percent, lightning surge damage at 14 percent, and vandalism at 11 percent. Maintenance records reveal that scheduled preventive maintenance intervals are consistently exceeded due to personnel shortages and budget constraints. Dissolved gas analysis and oil sampling tests, recommended by IEC 60422, are performed on fewer than 15 percent of the transformer population annually. The study benchmarks current maintenance practices against the IEC condition-based maintenance framework and identifies critical gaps. Transformer overloading is linked to unauthorised service connections and population growth outpacing network capacity expansion. Recommendations include adoption of an automated transformer monitoring system, strict overload protection relay settings, and a condition-based maintenance programme supported by periodic dissolved gas analysis. Keywords: transformer failure, maintenance practices, distribution network, Lagos, power outage.