MV System Earthing

[Vegemite]

Are there examples of either industrial or utility MV (approximately 1 to 33 kV) distribution systems operating without any form of system earth. By any form I exclude even voltage transformer earthing. I mean fully floating.

 

[waross]

In the first half of the century 440 volt ungrounded delta secondary industrial systems were common. The insulated conductors in conduit formed a capacitor that gave a reference to ground on a system of any size. Not much current. Enough to get a reading on a voltmeter. On a large system enough current to kill you but not enough to burn you. Some old timers would check for voltage by grounding the end of a piece of #14 copper and scratching the other end across the hot terminal. They would get a small spark from the capacitor charging current.
The other connection to ground was the three "Ground detector lights." If you got a ground on one phase one of the lights went out. Usually neon lamps about an inch in diameter were used. I once met an old electrician about a week after he used the old method on a new 1000 KVA 277/480 solidly grounded transformer. His hands were still in bandages the size of boxing gloves.

yours