Flooded underground electrical vaults 1

[dvd]

Recent news footage of flooding in New York City got me wondering what the electrical safety on medium and high voltage equipment in (flooded) underground electrical vaults consists of. Is there something akin to gfci that prevents people nearby from getting electrocuted? Would appreciate any discussion.

 

[davidbeach]

Anything in vaults should be suitable for submerged operation. The stuff in normally dry basements would be of more concern. Nothing similar to a low voltage GFCI, but also no low current leakage, a bit of any sort of path to ground and there’s a fault that should trip something.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[dvd]

Thanks for the response, davidbeach.

 

[bacon4life]

For household electrocution prevention, there several possible approaches including:
1) The case of a tool/appliance can be grounded using a 3 prong cord. If the internal wiring shorts to the case, there will be high current flows that cause the circuit breaker to trip.
2) A GFCI compares the amount of current flowing on the neutral and phase wires, and trips if they differ my more than a small amount.

Any MV/HV cable will have a grounded metallic shield as part of the outer covering of the cable, so it is similar to using a 3 prong plug.

The bigger concern for electrocution is typically when bare overhead wire lands on high resistance ground like dry sand or dry asphalt. Wires can fall on the ground and remain energized for hours. Relay manufactures have been working on hi-z relays for many years, but the algorithms still need lots of work before they are ready for widespread deployment. This is why utilities recommend staying 50+ feet away from any downed power line.