Condition Monitoring and Predictive Maintenance of Power Transformers at Shell Petroleum Development Company Facilities, Port Harcourt

This study examines the condition monitoring techniques and predictive maintenance practices applied to power transformers at Shell Petroleum Development Company facilities in Port Harcourt, Rivers State, South South Nigeria. Power transformers are critical and expensive assets in the oil and gas electrical infrastructure, and unexpected failures can cause costly production outages, environmental incidents, and safety hazards. The study evaluates the effectiveness of the condition monitoring programme through a review of three years of dissolved gas analysis results, oil quality test data, partial discharge measurement records, and thermal imaging survey reports for 18 transformers across three onshore SPDC facilities. Condition data were assessed using the IEC 60599 gas ratio method and the Duval Triangle for fault type identification from DGA results. Comparison of predicted fault probabilities against actual maintenance findings during scheduled overhauls was used to evaluate condition monitoring predictive accuracy. Results show that dissolved gas analysis correctly predicted incipient thermal faults in four transformers before visible degradation occurred, enabling planned maintenance that avoided unplanned outages. Partial discharge measurements identified dielectric weakness in two transformers not yet detected by DGA, suggesting that both techniques are complementary. Oil quality analysis reveals that one-third of monitored transformers have moisture levels exceeding the IEC 60422 threshold, attributable to ageing gaskets and insufficient oil sampling frequency. Recommendations include reducing the DGA sampling interval for transformers above 15 years of age and integrating online DGA monitors on the six highest-criticality units. Keywords: transformer monitoring, dissolved gas analysis, predictive maintenance, condition assessment, Port Harcourt.