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I worked for a switchgear manufacturer in my early working life and we had a unit called a T4GF3 (I think) which was a fused ring main unit - 3 phase 11kV 630A normal current. It had 3 fuses feeding the transformer outlet at the back. These had an explosive charge which fired a pin out of the end to trip a mechanism to prevent loosing a single phase. The fuses were (from memory) 14" (~35cm) long and 2.5" (6.2cm) diameter. One of the jobs I had was to design a simulator of the explosive pin and then a compound pendulum to measure the energy transferred. BTW, the fault current was 21kA!!!
That's probably how it was in service. If it's not locked someone (normally kids) will find a way to switch it. Also, the top is both bolted and locked down for the same reason. When I worked there, one Monday we got a fault report from a switch that had failed (!!!!). Three 10 year old boys had decided it would be funny to blackout the area and the switch had an oil level indicator on the front. They broke the indicator and poked umbrella spokes through the hole. When the spokes reached the bus bars, the oil (250L) instantly boiled and ignited. All three were killed in the subsequent explosion. After that, all access points had to be locked and the oil level indicator removed.Got enough padlocks on it
