North American transformer outage rates and durations in assessment of transmission system reliability and availability

The North American Electric Reliability Corporation (NERC) uses transmission equipment inventory and outage data to analyze outage trends to assist in identifying significant reliability risks to the bulk power system (BPS). These risk areas enable NERC to identify priority projects that provide coordinated and effective solutions to these identified risks to the reliability of the BPS. This paper presents the framework of statistical analysis of transformer outage data to identify outage trends across voltage levels. This paper presents the first study of the North American combined inventory and outage data for both automatic and non-automatic outages of transformer. The results of this analysis can be used as input to value-based transmission and distribution reliability planning, as well as for probabilistic based operations and equipment maintenance of transmission systems.