Any high voltage equipment will typically behave to a power system and power system environment where it is installed and operated. Because of it, high voltage equipment operated in tropical countries has a different characteristic compare to the one operated in temperate countries. Different symptoms and failure modes have been observed. As a consequence, different approach of inspectons ,assessments and hence treatments should be applied to achive a long term perfomance of the equipment. Besides aforemetioned technical espects, long term equipment perfomance may also be influenced by non-technical aspects, such as utulity's policy on installation operation and maintenance and customer demand on reliability and quality of power energy transmission. Not to mention general constain faced by any utulity in the world: financial. Thus, in order to attain a reliable yet economic power system operation and maintenance, PLN P3B jawa Bali as a unit which responsible for dispatching and controlling the transmission grid, nneds to develop an overall equipment assessment system. In the developedment of such system P3B jawa bali needs to consider tecnical as well as non-technical aspects. An overall assessment system for power transformer is given as the example of how the utility deals with those aspects.