Advanced transformer condition assessment – Part I

Infrared Thermography, Ultrasonic Noise Analysis, Partial Discharge Detection, Dissolved Gas Analysis, Vibration Analysis – all these techniques are great stand-alone diagnostic tools; however, when used properly, combining the data obtained through each technique, an incipient fault can be identified long before it degrades the insulation and creates a failure. This paper will provide guidance in setting up a complete Predictive Maintenance program to be able to provide owners of oil-filled power transformers (4 kV and up), i.e. utilities, refineries, military, mining, etc., with a complete health report and condition assessment of critical oil-filled power transformers and ancillary substation components. The testing described in this paper is done on energized, fully loaded transformers. Author’s vast experience with doing Partial Discharge testing reveals that nearly 80 % of all oil-filled power transformers exhibit some PD. This low level PD activity is not detrimental to the health of the transformer. It is usually a burr or sharp corner that is producing the activity. I consider this just nuisance PD and most times it continues for the entire life of a transformer without a failure related to PD