Dissolved-Gas Analysis for Nitrogen-Blanketed Transformers

Nitrogen-blanketed transformers gradually flush out oxygen and fault gas in the course of temperature-driven headspace pressure regulation. Consequently it is possible in many such transformers for intermittent or moderate fault gas production to go unrecognized if fixed limits are used to detect abnormal gassing. The use of cumulative data and fault energy indexes can partly counteract the effect of gas loss and make fault gas production apparent. Four examples are discussed to show how this works.