Transformer condition assessment for maintenance ranking: A comparison of three standards and different weighting techniques

Transformer condition assessment is an important asset management exercise for utilities. Currently, there is no universal method adopted for accomplishing this task. This paper looks at condition assessment of transformers for maintenance ranking based on criteria of three different standards; IEEE, Bureau of Reclamation (BoR) and California State University Sacramento (CSUS). Each of these have their own limits pertaining the assessing variables of what they consider acceptable or unacceptable. Field data of transformers were gathered and normalized based on these limits, then transformed into fuzzy variables and subsequently synthesized into health indices using evidential reasoning approach. These health indices were applied to assess the maintenance need of the transformers which were then ranked for maintenance in a descending order. Ten transformers are used for the purposes of illustration. The result from the three standards with inputs assigned different weights were compared by use of these health indices and the ranking correlation coefficients. The results demonstrate that standard and weighting adopted influences the transformer health index and ranking.