Assessment of Condition Monitoring Techniques for Power Transformers at Transmission Substations in Kaduna State

Power transformers are the highest-value assets in electricity transmission infrastructure, and unexpected failures at substations in Kaduna State, North West Nigeria, result in widespread outages affecting industrial production and residential supply across large geographic areas. This study assesses the application of condition monitoring techniques for early detection of developing faults in power transformers at four transmission substations operated by the Transmission Company of Nigeria in Kaduna. Dissolved gas analysis of transformer oil, partial discharge measurement, infrared thermography, and transformer turns ratio testing are evaluated as the primary condition monitoring modalities. Monitoring data were collected quarterly at each substation over an 18-month period and interpreted using IEC 60599 DGA fault interpretation guidelines and manufacturer nameplate reference values. Findings revealed that two transformers at the Rigasa substation exhibited DGA signatures consistent with moderate thermal faults in oil, one of which subsequently failed within three months of the anomalous reading. Partial discharge activity was detected in three transformers across the study sites at levels warranting intensified monitoring. A condition-based maintenance framework is developed based on the study findings, prioritizing monitoring frequency and intervention thresholds for each fault indicator. The study evaluates the organizational and technical readiness of TCN Kaduna to implement the recommended framework, identifying training, equipment procurement, and data management requirements. Keywords: condition monitoring, power transformer, dissolved gas analysis, substation maintenance, Kaduna State