Spraying Foam Water on Live Electrical Equipment

[mbrooke]

NFPA did some testing on spraying water and foam agents on live electrical equipment, including a few tests involving 345,000 volts in a New York City (Staten Island) Substation. Surprisingly current was only in the micro to milli amp range. Fascinating stuff:

https://www.nfpa.org/assets/files/AboutTheCodes/18A/18A_F2016_WAB_AAA_SD_Ballot_final%20(002).pdf

https://imgur.com/oMr9E3G

https://imgur.com/c2pKQlU

 

[gadfly56]

Water-mist fire extinguishers are already approved for use on electrical equipment, but I'm not sure if the cutoff is 240 or 600 volts.

Amerex Water-mist

 

[PaulMmn]

Myth Busters tested to see if P on an electric fence or the third rail was hazardous. 3rd rail was generally found to be non-electrifying--the stream breaks up into droplets, less likely to be hazardous. Electric fence was more hazardous, since it was higher off the ground and the stream was more intact when it hit the fence.

However, google did find some references where these findings were not confirmed.

For substations-- are there cases where a severe rain storm causes problems??

Transmission lines are 'iffy--' I was on a campout one rainy weekend-- not so much rain, but mist. The way to the camping area passed under a transmission line (no idea how much voltage). I was walking with my umbrella up-- metal frame. As I passed under the power line, I felt a tingle. I quickly folded my umbrella!

 

[mbrooke]

Myth Busters tested to see if P on an electric fence or the third rail was hazardous. 3rd rail was generally found to be non-electrifying--the stream breaks up into droplets, less likely to be hazardous. Electric fence was more hazardous, since it was higher off the ground and the stream was more intact when it hit the fence.

However, google did find some references where these findings were not confirmed.

For substations-- are there cases where a severe rain storm causes problems??

Transmission lines are 'iffy--' I was on a campout one rainy weekend-- not so much rain, but mist. The way to the camping area passed under a transmission line (no idea how much voltage). I was walking with my umbrella up-- metal frame. As I passed under the power line, I felt a tingle. I quickly folded my umbrella!

Typically heavy rain does nothing. Maybe if the insulators are really dirty, but by design heavy rain will not cause a flash over.

 

[garbo]

I had a customer that had water fire extinguishers in one room that they told was deionized water. It left no film and easy clean up.

 

[paulengr]

Myth Busters tested to see if P on an electric fence or the third rail was hazardous. 3rd rail was generally found to be non-electrifying--the stream breaks up into droplets, less likely to be hazardous. Electric fence was more hazardous, since it was higher off the ground and the stream was more intact when it hit the fence.

However, google did find some references where these findings were not confirmed.

For substations-- are there cases where a severe rain storm causes problems??

Transmission lines are 'iffy--' I was on a campout one rainy weekend-- not so much rain, but mist. The way to the camping area passed under a transmission line (no idea how much voltage). I was walking with my umbrella up-- metal frame. As I passed under the power line, I felt a tingle. I quickly folded my umbrella!

Rain water is not very conductive. Even in hurricanes. Dirt plus water is bad. A fine mist or heavy dew onto dirty insulators is where the worst is done. The worst is horizontal rain getting into indoor areas or filling up areas assumed to be dry or drain.

As an example rubber gloves are filled with water inside and out to test and hot sticks are soaked. So they simulate line work in rain.

As to the umbrella story you are between a ground and a phase conductor. It’s capacitive coupling at work plus you are bridging several feet of local space creating a local “short” and likely picking up a little bit of either the inductive field or capacitively coupling.