in steam turbines 364MW Units equipped with electronic main and back up over speed protection system ,how often should we perform real over speed test.
in 400 MVA transformer we get every night first stage alarm at , we noticed that the alarm comes when the ambient temperature is low and unit load is low. we susbect air ingress during low temperature time when both oil and air temperature are at thier lowest value.
we performed DGA for the oil...
