Wanted to bump this up and add that I've also heard some motor contactors/overload relays emit a high-pitched squeal during motor starting....
Many years ago I also saw pictures of destructive testing of industrial switchgear..copper buss as big as one's leg were distorted into odd shapes, insulating supports totally destroyed, and the test engineers were reportedly knocked out of their chairs in the bunker by the blast!!
The fault current in the test was over 2 MILLION amps!! Yikes!! (I think the voltage was 4Kv.)
