13800 volts in vault

[kbrandt]

Hi guys,
I have a chance to do a job that requires pulling 1/0 thru 2 vaults (7x7) or bigger and splicing them in the vault. They either have 41600 or 13800 cable already in vault (have not ask but will before I bid) . They are spliced and go thru also, nothing is exposed just cables running thru.

How close can you get to these cables? And is there any problem working in the vault with these cables at such high voltage.

Have not been around that much high voltage and want to go home at night. Good money but not worth going to the light just yet.

Would you do the job? Or is it not that big of a deal? You know what I mean.

Thanks for any help.

 

[zog]

The MV cables are going to be energized while you are down there? For a reference the 70E requires HRC 4 PPE for a MV insulated cable "examination" in a manhole or vault, so if you are pulling cable and may move, disturb, lean on, etc.... those energized cables you should be in a 40 cal suit.

 

[jimmac49]

Blast Blankets

Blast Blankets

I would hang blast blankets in the vault while working there. They will give you some protection, isolation and seperation in case there is a cable or splice failure. They are not for insulation purposes. I think the are made by Salisbury or Hubbell. If it is possible to get an outage on the circuits in the vault even if was a weekend or an off shift that would be the safest option.

 

[jeremysterling]

Blast blankets

Blast blankets

I would hang blast blankets in the vault while working there. They will give you some protection, isolation and seperation in case there is a cable or splice failure. They are not for insulation purposes. I think the are made by Salisbury or Hubbell. If it is possible to get an outage on the circuits in the vault even if was a weekend or an off shift that would be the safest option.

First off, I am not qualified to respond to the OP. IMO, try to get an outage.

I wanted to thank jimmac for posting about these blankets. I've always heard of building a "rubber room" with insulating rubber mats, but I see more protection coming from "blast blankets."

I googled "arc flash blankets" and found several on line distributors. I am going to ask the boss about acquiring some of these.

 

[Hv&Lv]

Is it 41,600 or 13,800? That is quite a spread. The shielded MV cables are safe to work around, you just need to know how to meet 70E provisions. I work around 25kV URD cables almost everyday. Pulled in 500' of new cable today for a job. The XF we came from was hot also. This cable is really no different than working around 600 volt cable. As long as the cable insulation is rated for the voltage it is carrying, it is fine. Where you will run into trouble is pulling the new wire in and abrading the energized cable. This is a big No-No! especially on concentric neutral cable. Jacket CN cable can handle rougher treatment, but don't get into that habit. Forget blast mats. In a 7X7, you will have no room. Get a couple of rubber blankets, drape them over the hot cable before entering the vault or pulling cable. http://www.westernsafety.com/salisburyelectrical/salisburyelectricpg3.html
One other thing, Wear rubber gloves always. Do NOT connect the neutral of the new cable to the neutral of the old cable bare handed. Even cable that has been stood off and isolated can still be carrying neutral currents in a loop feed situation.

 

[Strathead]

Is it 41,600 or 13,800? That is quite a spread. The shielded MV cables are safe to work around, you just need to know how to meet 70E provisions. I work around 25kV URD cables almost everyday. Pulled in 500' of new cable today for a job. The XF we came from was hot also. This cable is really no different than working around 600 volt cable. As long as the cable insulation is rated for the voltage it is carrying, it is fine. Where you will run into trouble is pulling the new wire in and abrading the energized cable. This is a big No-No! especially on concentric neutral cable. Jacket CN cable can handle rougher treatment, but don't get into that habit. Forget blast mats. In a 7X7, you will have no room. Get a couple of rubber blankets, drape them over the hot cable before entering the vault or pulling cable. http://www.westernsafety.com/salisburyelectrical/salisburyelectricpg3.html
One other thing, Wear rubber gloves always. Do NOT connect the neutral of the new cable to the neutral of the old cable bare handed. Even cable that has been stood off and isolated can still be carrying neutral currents in a loop feed situation.

So, are you saying it is ok to climb around in an energized 4160 or 13800 vault without a flash suit or other provisions such as no metallic clothing and means of assuring isolation from faulty cable insulation? Being a 480 volt electrician, that would scare the crap out of me. We are starting to do a little MV work and I have wondered the same things as the OP. I have followed this thread with some interest. I do realize that the awe I sometimes feel for MV workers is probably similar to the awe fest by civilians toward any electrican, but still...

 

[zog]

First off, I am not qualified to respond to the OP. IMO, try to get an outage.

I wanted to thank jimmac for posting about these blankets. I've always heard of building a "rubber room" with insulating rubber mats, but I see more protection coming from "blast blankets."

I googled "arc flash blankets" and found several on line distributors. I am going to ask the boss about acquiring some of these.

They are effective if used correctly, here is a test video.
http://www.youtube.com/watch?v=WkSAsugKhO8

 

[barclayd]

You say you 'have a chance to do a job'. Does that mean you have a chance to BID on a job? Splicing medium-voltage cables is a very precise task. It is hard enough under ideal conditions, but can be daunting in the confines of a manhole. I would probably not even consider your bid unless you have at least 5-years of experience.
good luck
db

 

[zog]

You say you 'have a chance to do a job'. Does that mean you have a chance to BID on a job? Splicing medium-voltage cables is a very precise task. It is hard enough under ideal conditions, but can be daunting in the confines of a manhole. I would probably not even consider your bid unless you have at least 5-years of experience.
good luck
db

I missed the "have not been around that much high voltage" part. I agree, if you have not been trained properly on MV systems, safety, MV cable construction, MV splicing, confined space requirements, etc.....I would not even consider bidding this job. MV splicing is somewhat of an art form, takes years of practice and one minor dfect will cause a cable failure. Think about paying for all of that cable when it blows up. Like this http://www.youtube.com/watch?v=6s3iLr9uY_A&feature=related

 

[Hv&Lv]

So, are you saying it is ok to climb around in an energized 4160 or 13800 vault without a flash suit or other provisions such as no metallic clothing and means of assuring isolation from faulty cable insulation? Being a 480 volt electrician, that would scare the crap out of me. We are starting to do a little MV work and I have wondered the same things as the OP. I have followed this thread with some interest. I do realize that the awe I sometimes feel for MV workers is probably similar to the awe fest by civilians toward any electrican, but still...

ABSOLUTELY NOT! I have been installing, and terminating 25kV cable for 25 years+. I have yet to "climb around" energized primary cable. My first suggestion would be proper training if you are planning on confined spaces with this cable. I may have been mistaken, but I had assumed we were talking about a splice vault (pull vault) 7X7. there is no need to climb in these vaults in order to pull in new cable and terminate it.

 

[kbrandt]

The wires to be pulled in and spliced are 1/0 copper 480 volt. But will be in same vault as high voltage cable. I may be able to de energize but I doubt it.