Let's put one of my experiences in which comes to mind.
I was working for the POCO, then Power New Zealand, in the metering department, around ± 1996 - 97, when I upgraded quite a few CT meters, when tariffs changed from 2 rate to T.O.U. metering in commercial installations.
I did a meter change at the Parakai Hotpools, Helensville, NZ and pulled the PT fuses of the CT meter to prepare for a meter change.
At the same time the contactor from the 100 HP hydroslide motor dropped out with a loud clunck, all the other filter pumps stopped and the lights went out as well, Within seconds the pool owner rushed in and said " Did you turn the power off?" , "No!", I said, "Why did it go off!" , "don't know", I said back, while checking the main switch at the same time if I didn't accidentally tripped the Main switch.
I had a chat with the owner and explained that the CT meter does not require a shutdown for a meter change.
Power remained off for about 20 minutes, then everything started up again.
When power was restored I checked the voltages at the isolation points and all was fine, and continued with replacing the 2 rate meter, and doing the necessary CT checks to confirm multiplier and CT tappings etc.
Later that day I heard that a Tornado knocked out the 11 kV feeder line to Parakai, hence the power cut.
It took the faultman about 20 minutes to isolate the damaged section of line and back feed the area from a different circuit.
