Working during a Thunderstorm

He's a question for you.

What (if any) are the dangers of working INDOORS on an electrical circuit during a Thunderstorm ? Heck you would have to be stupid to work outside in one, but I was considering what would happen if there was a nearby strike and I was working on an open consumer unit connecting up say a new radial circuit. Could a sufficient induced voltage into the ground and incoming cable cause a voltage/current on all the incoming cables including the earth bonding, thus giving me or anyone nearby a nasty shock ?

I ask because I am doing something like that today. I've completed all the outside electrical work, and I was scheduled to hook it all up into their consumer unit this afternoon, so only working indoors, but with a cable going outside, and the Met Office have just issued a weather warning of severe thunderstorms later today.

Curious as to what you would do, and whether my theory above is correct. Would you do the work, or wait until the storm has passed, or reschedule ?

You wouldn’t be holding onto a live conductor anyway even if there was a surge.

Working on equipment if lightning struck an earthed pylon or something outside, no different from sitting in a metal bath inside during a storm.

You would hope the earthing arrangements external to the house would deal with it all.

I think it would also come down a bit to how exposed the house / supply is. In a city with taller buildings nearby and underground cables, probably low risk. In a rural site with house exposed and/or supply overhead then I would not be working close to incoming cables.

A supply isolator switch, for example, out to survive a good few kV surge when open (not sure spec, but probably 8kV), but enough voltage and it would jump.

This is one of those questions that you never really think about until......

Always remember when I was quite young that we were not allowed to watch TV if there was a thunderstorm and the TV aerial had to be unplugged to stop those nasty lightining strikes damaging the TV

About 20 - 25 years ago I saw the damage a lightining strike to the mains caused at a hospital obviously all the circuits were live at the time of the strike and some of the intruder alarm equipment we were called in to replace suffered flashovers internally which cleary indicated the magnetude of spike. Most of this was replaced while there was still a possibility of other other strikes and not a lot of thought was given to any special precautions in case it happened. I suppose having to replace / repair about 20 intruder alarms on a Sunday with 2 on call staff

I worked on a comms mast a number of years ago on Jersey and one of the jobs was for the Jersey states we had a guy on the phone getting minute by minute updates on an incoming lightining storm from the Jersey met office while we fixed some equipment on the mast, completed the job with the storm 10 miles away so it was a quick climb down from 55m and get a safe distance from the mast yes everything was properly earthed but I didn't want to be too near it to prove it was safe

I would think a properly isolated circuit would pose a minimal risk