Method for effects evaluation of some forms of power transformers preventive maintenance

The paper suggests a method for effects evaluation of a few activities and measures, undertaken as a part of preventive maintenance of power transformers. The method enables calculation of expected failures repair cost and load curtailment cost. The method identifies minor and major failures. Power transformer is a complex system, consisting of five components (functional parts). It is assumed that each component has two independent, competing failure modes: wear-out failure mode, modeled by two-parameter Weibull distribution, and a chance failure mode, characterized by an exponential distribution. The application of the method is demonstrated for one transformer station (TS) 110/x kV/kV with 2 × 31.5 MVA transformers. Also, by applying the method, influence of system for condition monitoring of transformer windings and oil on failures repair cost and load curtailment cost is evaluated.