Got Shocked By 480V. Still Not Sure How

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bthouse

Member
Location
St. Louis, MO
I recently was shocked with 480V. I am 4 weeks into my recovery. Haven't been cleared to return to work yet. However, I feel fortunate that my injuries sustained from my brush w/ 480 should heal in another month. What really bothers me is that I'm still not 100% certain how the current entered body the way it did. Here's how it all went down. I was working on an old 2000amp 277/480V outdoor switch gear. We installed a fusable disconnect beside the gear for a new sub-panel located elswhere. I was connecting the disconnect feeders to one of the open lugs on the bus. Why we didn't shut off power and attempted this hot is a whole other story. The disconnect that I was wiring was locked out, tagged out, and fuses were not yet installed. The gear was bottom fed. The neutral and ground bus were bonded together and to the the enclosure frame. The grounded bus was located close to the front of the panel enclosure door. Approx 6" behind the neutral/ground bus was the B phase bus lugs and 6" behind that was the A and C phase bus lugs. I terminated the ground and neutral first. I had on my hot gloves (rated 1000V)
with leather protectors. I had a 10,000V insulated mat beneath me. I was not however wearing an arc flash suit. I know how incredibly reckless and stupid it was not to wear the suit. Trust me. It's a mistake I'll never make again. I was loosening the B hase lug with a plastic socket wrench. I was pulling my hands out of the gear when I got hit. It hit me like a Mack truck. I couldn't see. Everything went white. I wanted to jerk my head back to try and break free. But I was paralyzed. Then everything went black. I don't know how long I was unconcious. When I came to, I was about 3 feet back from the gear. My gloves were still on and in tact. I had a 1/2 dollar sized hole in my forearm. I had no other physical marks on me. I don't know if the hole in my forearm was the entry or the exit. The only thing near that part of my arm was the grounded bus. If my exposed forearm touched the gounded bus it would make sense that my body somehow made a phase to ground connection, right? If my arm was the only thing that made physical contact with a bonded neutral and I was on an insulated mat, how and/or why would current flow through me unless I was completing a circuit? I appreciate any input on the topic. Thanks.


For all of you out there in the field....BE SAFE!!! DON'T EVER LET TIMELINES OR JOB COST INFLUENCE YOUR JUDGEMENT AND DECISIONS PERTAINING TO SAFETY!!!!
 

LEO2854

Esteemed Member
Location
Ma
I recently was shocked with 480V. I am 4 weeks into my recovery. Haven't been cleared to return to work yet. However, I feel fortunate that my injuries sustained from my brush w/ 480 should heal in another month. What really bothers me is that I'm still not 100% certain how the current entered body the way it did. Here's how it all went down. I was working on an old 2000amp 277/480V outdoor switch gear. We installed a fusable disconnect beside the gear for a new sub-panel located elswhere. I was connecting the disconnect feeders to one of the open lugs on the bus. Why we didn't shut off power and attempted this hot is a whole other story. The disconnect that I was wiring was locked out, tagged out, and fuses were not yet installed. The gear was bottom fed. The neutral and ground bus were bonded together and to the the enclosure frame. The grounded bus was located close to the front of the panel enclosure door. Approx 6" behind the neutral/ground bus was the B phase bus lugs and 6" behind that was the A and C phase bus lugs. I terminated the ground and neutral first. I had on my hot gloves (rated 1000V)
with leather protectors. I had a 10,000V insulated mat beneath me. I was not however wearing an arc flash suit. I know how incredibly reckless and stupid it was not to wear the suit. Trust me. It's a mistake I'll never make again. I was loosening the B hase lug with a plastic socket wrench. I was pulling my hands out of the gear when I got hit. It hit me like a Mack truck. I couldn't see. Everything went white. I wanted to jerk my head back to try and break free. But I was paralyzed. Then everything went black. I don't know how long I was unconcious. When I came to, I was about 3 feet back from the gear. My gloves were still on and in tact. I had a 1/2 dollar sized hole in my forearm. I had no other physical marks on me. I don't know if the hole in my forearm was the entry or the exit. The only thing near that part of my arm was the grounded bus. If my exposed forearm touched the gounded bus it would make sense that my body somehow made a phase to ground connection, right? If my arm was the only thing that made physical contact with a bonded neutral and I was on an insulated mat, how and/or why would current flow through me unless I was completing a circuit? I appreciate any input on the topic. Thanks.


For all of you out there in the field....BE SAFE!!! DON'T EVER LET TIMELINES OR JOB COST INFLUENCE YOUR JUDGEMENT AND DECISIONS PERTAINING TO SAFETY!!!!

Thank god your ok.When pulling your arms out you must have hit one phase and your left arm hit the neutral bus and the grouned frame . If the neutral and ground were not properly bonded then touching the neutral and ground will make you the bond. SEE NFPA 70E
 

dbuckley

Senior Member
You are a very lucky bunny indeed. A passing touch at those sorts of voltages hurts like hell, but you were arm deep in big electricity and somehow got in its way, and lived to tell the tale.

Is there any sort of official investigation being carried out to determine what happened?
 

busman

Senior Member
Location
Northern Virginia
Occupation
Master Electrician / Electrical Engineer
I'm glad you're going to make a full recovery. This is one of the reasons that I don't use Class 0 gloves anymore. I don't feel that the 11" length that is the most common is adequate. I use a pair of 16" Class 1 gloves (come all the way to my elbows). I also appreciate the extra thickness of rubber. Never really felt comfortable with 1000V gloves on 480V system. It does reduce dexterity somewhat, but you get used to it. I also have a pair of sleeves that I use if something is extra hairy.

BTW - still not advocating hot work.

Mark
 

cornbread

Senior Member
It's great your recovery is going well and I appreciate you sharing your story. I often use stories like your to re-enforce the need for using hot work permits and proper PPE.
 

sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
Then you were hit with 277volt not 480v if it wasn't phase to phase; sounds like you were pulling the load of more than your body see LEO2854 reply.
good luck, get well, wait till you have to get back in the saddle you will pucker a bit.
 

bthouse

Member
Location
St. Louis, MO
Thank god your ok.When pulling your arms out you must have hit one phase and your left arm hit the neutral bus and the grouned frame . If the neutral and ground were not properly bonded then touching the neutral and ground will make you the bond. SEE NFPA 70E

Well that's the thing. When I pulled my hands out I should of had at least a 4-6" clearance between my hands and the closest phase. The gloves were brand new and showed no signs of damage. And the ground & neutral are connected to the same bus. So I know they were bonded together. As far as bonding the eclosure and frame I cannot remember actually seeing a bond between the grounded bus and the frame. Doesn't mean it wasn't there. I just do not remember seeing it.
 
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cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
First thank goodness you're ok.

I was watching a show on how they rescue guys that are hurt on high voltage towers and they said the reason so many people get hurt on them is that they don't know, is that at those voltages, electricity can jump _____ ft with out you ever touching anything. I just don't remember how far they said.

Anyone out there know?
 

bthouse

Member
Location
St. Louis, MO
Then you were hit with 277volt not 480v if it wasn't phase to phase; sounds like you were pulling the load of more than your body see LEO2854 reply.
good luck, get well, wait till you have to get back in the saddle you will pucker a bit.

I would agree that most likely I was hit with 277V. I labeled this post "Shocked by 480V" mostly to reference the system voltage. Even though I should have specified 277/480V. Also, The Burn Center's plastic surgeon that trated me told me of another patient that he was treating. He was hit with 480V and his injuries were almost identicle to mine. Only difference was his heart stopped and had to be recessitated. I was just knock unconssious. It took me 2 days to regain full use of my legs. Since brunt of my injuries are in my right arm, I don't think the electricity crossed my heart. In any case wether it was 277V or 480V the lesson to be learned from this is the same.
 

bthouse

Member
Location
St. Louis, MO
You are a very lucky bunny indeed. A passing touch at those sorts of voltages hurts like hell, but you were arm deep in big electricity and somehow got in its way, and lived to tell the tale.

Is there any sort of official investigation being carried out to determine what happened?

The claims adjuster from workman's comp. said they were launching an investigation. They said they were going to test my gloves and safety mat. And they said they were going to send an engineer to the site and inspect the gear. This was about three weeks ago. Haven't heard anything yet.
 

bthouse

Member
Location
St. Louis, MO
First thank goodness you're ok.

I was watching a show on how they rescue guys that are hurt on high voltage towers and they said the reason so many people get hurt on them is that they don't know, is that at those voltages, electricity can jump _____ ft with out you ever touching anything. I just don't remember how far they said.

Anyone out there know?

You know I thought about that. The part that makes me think this is probable is the fact that this gear was outside and we were in the middle of a heat wave. So I was pretty sweaty. And I know that sweaty skin greatly reduces your body's resistance, making it a much better conductor. The live feeders inside the gear were probably pulling at least 1000amps. So I imagine the magnetic field inside that gear was pretty high. But, I thought voltages needed to be much higher than 480V (like in transmission lines) before they will arc through the air.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
You know I thought about that. The part that makes me think this is probable is the fact that this gear was outside and we were in the middle of a heat wave. So I was pretty sweaty. And I know that sweaty skin greatly reduces your body's resistance, making it a much better conductor. The live feeders inside the gear were probably pulling at least 1000amps. So I imagine the magnetic field inside that gear was pretty high. But, I thought voltages needed to be much higher than 480V (like in transmission lines) before they will arc through the air.

You may be right about it needing to be a higher voltage. I got hit once with 277, but I know what happened, but I have been shocked a few times where I would have sworen that I didn't touch anything.
 

zog

Senior Member
Location
Charlotte, NC
I would agree that most likely I was hit with 277V. I labeled this post "Shocked by 480V" mostly to reference the system voltage. Even though I should have specified 277/480V. Also, The Burn Center's plastic surgeon that trated me told me of another patient that he was treating. He was hit with 480V and his injuries were almost identicle to mine. Only difference was his heart stopped and had to be recessitated. I was just knock unconssious. It took me 2 days to regain full use of my legs. Since brunt of my injuries are in my right arm, I don't think the electricity crossed my heart. In any case wether it was 277V or 480V the lesson to be learned from this is the same.

The "path" and smyptoms are not always as clear as most people think. Dr Michael Morse is one of the nations leading experts on electric shock injury, you may want to look around his site. http://www.electricalinjury.com/EIinfo.htm
 

busman

Senior Member
Location
Northern Virginia
Occupation
Master Electrician / Electrical Engineer
480V will only "jump" about 1/2".

I'm guessing you mean 1/2" after the arc has been struck is the distance at which it will extinguish itself. From a physics website:

"The dielectric strength of air is approximately 3 kV/mm. Its exact value varies with the shape and size of the electrodes and increases with the pressure of the air."

This seems about right since I believe that car coils generate about 10-20 kV to jump a gap of just about a millimeter.

Mark
 

zog

Senior Member
Location
Charlotte, NC
I'm guessing you mean 1/2" after the arc has been struck is the distance at which it will extinguish itself. From a physics website:

"The dielectric strength of air is approximately 3 kV/mm. Its exact value varies with the shape and size of the electrodes and increases with the pressure of the air."

This seems about right since I believe that car coils generate about 10-20 kV to jump a gap of just about a millimeter.

Mark

Well I didn't look it up on a "physics website", just off the top of my head, and really 1/2" or less than 1/2" is a moot point for this discussion, IEEE 4 Appendix B lists the minimum distances for avoiding flashover, for 300-750V it is 2mm.
 
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