ABSTRACT
The monitoring and diagnostics of transformers have attracted considerable attention of researchers and practicing engineers. The monitoring can be either offline or online. The monitoring not only detects the incipient faults but also allows a change from periodic to condition-based maintenance. It is important to identify key parameters that should be monitored to reduce the cost of the overall monitoring system. There are a number of offline and online monitoring/diagnostic techniques that are currently being used and developed further. More sophisticated dielectric diagnostic methods determine the moisture in solid insulation from dielectric characteristics such as charging/discharging currents, recovery voltages, and the dissipation factor. These methods, which can be used for doing on-site diagnostics, are generally more accurate than the conventional methods. The sensors used in gas-insulated substations have been successfully applied for ultra high frequency diagnostics of transformers.
