Comparison of Risk Assessment Schemes for Maintenance Prioritisation of Power Transformers

Failure Modes, Effects, and Criticality Analysis, and risk matrix analysis are compared to plan maintenance models and prioritise power transformers by applying both weight and score techniques. The Failure Modes, Effects, and Criticality Analysis is relevant to severity, occurrence, and detection criteria to establish a criticality or a risk priority number. Scores of severities, occurrence, and detection are compared to their limitations with five risk levels: minor, marginal, moderate, critical and catastrophic. For the risk matrix analysis, component condition index and importance index are concerned with setting up the matrix. Subsequently, risk distance is measured. Maintenance action and prioritisation of both risk assessment schemes are determined and compared. The action is grouped into four models: low, medium, high and very high criticality. In failure analysis, 52 transformers rating 115 kV and 30 transformers rating 230 kV in Thailand are focused. Available major failures on main 115 kV components: winding, on load tap changer, and bushing are reviewed for maintenance model. Consequently, the transformer components are prioritised for their maintenance action to maximise the lifespan.