| Popis: |
Condition based maintenance strategies in power transformers typically evaluate the risk of failure associated with the transformer by evaluating various parameters, one of which is dissolved gas analysis (DGA). Typically, offline DGA is performed once or twice a year. However, with sick transformers – transformers which show either an increase in fault gas levels or an increase in fault gas rates; manual sampling interval needs to be increased accordingly. This is when online DGA becomes effective. A diagnostic online DGA device allows to trend and diagnose faults within the transformer in near real time, which is the underlying strength of the online DGA device. In this paper, a case study is presented on an 85 MVA transformer, manufactured in the year 2000, where the concept of nursing sick transformer using online DGA monitor is presented. Using the concept of nursing, the transformer was kept in operation for a stipulated period which enabled delayed shutdown, continued operation of the sick transformer and subsequent replacement with a new transformer. |
