Can you increase gas levels on a 20mva transformer by tapping up with no load?

Question

just checking if that was the cause for the alarm on the bucholz relay

Answer 1

Tapping up on any transformer with an open secondary should reduce both i^2R losses and core losses, although not by very much.  Once load is applied, however, losses will increase appreciatively.  Other explanations might include low oil levels, oil deterioration or contamination, or the relay itself.