A Probabilistic Method for Establishing the Transformer Capacity Reserve Criteria for HV/MV Substations

This paper provides an extension of methods for computing reliability indices for substations which takes into account the permissible overload of the power transformer, the daily load cycle and emergency loading. Based on the reliability indices derived in this paper it is possible to determine a reliability criterion for the rating of the substation, the number of transformers and the reserve factor required, which have traditionally been based on conservative deterministic criteria.