Techniques and experience in on-line transformer condition monitoring and fault diagnosis in ElectraNet SA

With evolving maintenance strategies in the electricity industry internationally, there has been increasing pressure to develop improved techniques for condition monitoring. Specifically there has been a trade off between the speed and accuracy of testing. Traditionally, transformer condition monitoring involved high accuracy tests, which due to their duration, could only be performed on a discrete periodic basis. ElectraNet SA has experienced many limitations associated with this form of condition monitoring, and there has been a trend towards high speed on-line monitoring techniques for power transformers. Though these new techniques do not provide the level of accuracy found in traditional forms of testing, they overcome many of their limitations. This paper, describes ElectraNet SA's techniques and experience with power transformer monitoring.