Insulation of 440V in emergency generator room

soochow008

Dears,
A question about the insulation of 440v in emergency generator room occurs as follows:
while testing the insulation of 440v in emergency generator room, it was found that the index of the flush type megger in switchboard was stationary as the button of earth alarm pressed down; consequently, after confirming with the E/E, he said that it (the megger index) only worked once the system (440v emergency switchboard) was on-load. At that moment I was not sure about the authenticity of his speech, so please anyone do me a favour;
"whether it can only test the earth alarm function of 440 v in emergency generator room when the system is on-load or parallelled in, or other better explanations in order to clarify ";
at the same time, it was noticed that the 220v in emergency generator room tested in normal.

MANY THANKS,