Possibilities of the Diagnosis of Power Transformers on Site

Transformers are one of the most important and cost-intensive components of the electrical energy supply networks. A view of the age structure of the transformers with different utilities shows that many of the transformers are already since a long time in operation. Deregulation forces the utilities to cost saving. This fact and the high age of the transformers make the necessity for monitoring and diagnostic systems clear. In this contribution first the damage statistics of different components of a transformer is introduced briefly. Constructing on it the possibilities of different monitoring systems are described as basis for a diagnosis. The difference between on-line and off-line procedure is discussed. Chemical, electrical, dielectric and further not electrical procedures are presented in detail. The contribution ends with a view on the future of diagnostic procedures.