Techniques of on-line monitoring and diagnosis for transformer

The transformer is crucial for the energy conversion and transmission in the process of power transmission and distribution, and plays an important role in the security of grid. On-line monitoring and diagnostics provides a promising platform not only to help the operators to manage transformer in a targeted fault repair and maintenance manner, but also to avoid fatal accidents. This paper describes the technique of oil dissolved gas analysis (DGA) using combined diagnoses method based on Borda rule, which can improve the accuracy of the results. Partial discharge is both the symptom and reason of transformer insulation degradation. Technique of partial discharge monitoring can detect the level of PD and growth rate though pulse current, ultrasonic detection, ultra-high frequency detection method and detection of light. It indicates the changes taking place within the transformer or reflects solid insulation voids, metal particles, air bubbles etc. due to some defects arising. The DGA and PD is the most widely used on-line monitoring technique. If all the monitoring technology performs reasonably well, they can better help transformer operator to monitor the current state of operation and make decisions on continuing operation, maintenance or replacement.