Hello all, Wanted some education from the guro`s We had a 300a main just blow apart internally it appears yesterday.No one was injured thanks to the right hand turn on and turn away method.We meged all the lines and couldn`t find a problem anywhere. This circuit had been off for approx. 30-40 days.The area is not moist or damp, humidity maybe. It was a square D big frame I don`t have all info in front of me.If you guys could help shed some light on this it would be much appreciated.PS one of the crew already figured it out he says sh** Happens.Maybe he`s right but I figure we can do better.