Review and Implementation of Transformer Health Index Methods in line with the Development of a Condition Assessment Tool

Transformers are important equipment of the electrical power supply system. A transformer defect can lead to heavy damage on the equipment itself as well as to its surroundings. Therefore, a defect is coherent with high costs. Numerous transformers are in operation since several decades. Furthermore, in Germany an additional stress for the equipment yields from a rising energy input of regenerative sources. The situation of the distribution grid is additionally intensified by a delayed system expansion. Hence, a transformer condition assessment tool is in development, which will support transformer expert at their daily work. This tool provides automated measurement evaluation, generation of diagnostic statements as well as the determination of a transformer overall condition. Health index (HI) methods are approved techniques for determining the general condition of a transformer. Thus, they are important for a condition assessment tool also. An overview about actual HI methods was generated by a literature study. Afterward the most promising methods where selected and implemented for the condition assessment tool. This paper recapitulates the literature study as well as the selection criteria and the implementation of the most interesting HI methods.