Measurement techniques for transformer diagnostic

Power transformers are one of the most important and also expensive components of the electrical power supply. In electrical networks, power transformers are of essential importance as interface between different system voltage levels. Due to the long manufacture process they are one of the most critical and high-priced equipment and so this is one of the reasons why condition monitoring becomes more popular. Monitoring systems as a basis for diagnostics open possibilities for expanding the operation time, reducing the risk of expensive failures and allow several maintenance strategies. With different monitoring techniques, detailed information about the transformer condition can be received and this helps to minimize the probability of an unexpected outage. This paper gives an overview about different monitoring and diagnostic methods and techniques, especially some example in the area of partial discharge (PD) and the frequency response analysis measurement.