Insulated overhead power cables

[cornbread]

We have a 15 KV distribution system, insualted cables with concentric neutral, cables run overhead lashed on a messenger. We are doing some work near these cables and we have been ask to put blankets over them for additional protection and visibility. My question is what type of PPE do I need to wear to install the blankets. I want to spec out the right gear. Do I assume the cable is bare and take the worse case arc flash to determine my PPE based on that? My goal is to provide adequate protection without creating heat stress for the electrician putting on the blankets. Any help would be greatly appreciated.

On a side note we already requested the line be de-energized, however it was determined that shutting off the line posed a greater safety hazard.

 

[zog]

We have a 15 KV distribution system, insualted cables with concentric neutral, cables run overhead lashed on a messenger. We are doing some work near these cables and we have been ask to put blankets over them for additional protection and visibility. My question is what type of PPE do I need to wear to install the blankets. I want to spec out the right gear. Do I assume the cable is bare and take the worse case arc flash to determine my PPE based on that? My goal is to provide adequate protection without creating heat stress for the electrician putting on the blankets. Any help would be greatly appreciated.

On a side note we already requested the line be de-energized, however it was determined that shutting off the line posed a greater safety hazard.

If the cable is insulated and you will not be interacting with them I dont see anyreason to do anything, if fact I think you are creating a hazard by messing with them at all. You are better off hanging arc suppresion blankets between the cables and the work area if you do anything at all.

 

[drbond24]

How heavy are the blankets? Has someone determined that the extra weight won't damage the line or cause it to sag too low?

It's dangerous to turn it off, but not dangerous to stick your face right up to it while you hang blankets on it?

My number one rule for energized circuits is: Looky, no touchy.

Have a spotter whose job it is to do nothing but stand and watch the cable. He/she can yell if someone or something gets too close.

 

[weressl]

We have a 15 KV distribution system, insualted cables with concentric neutral, cables run overhead lashed on a messenger. We are doing some work near these cables and we have been ask to put blankets over them for additional protection and visibility. My question is what type of PPE do I need to wear to install the blankets. I want to spec out the right gear. Do I assume the cable is bare and take the worse case arc flash to determine my PPE based on that? My goal is to provide adequate protection without creating heat stress for the electrician putting on the blankets. Any help would be greatly appreciated.

On a side note we already requested the line be de-energized, however it was determined that shutting off the line posed a greater safety hazard.

The cables do NOT present touch hazard IF they are truly insulated cables, not just weatherproofed conductors. The hazard would be if the mechaniocal integrity of the insulation is compromised with some tools being mishandled or accidentaly strike the cable. The blanket would provide no protection against it. (Raincoat in a hailstorm; you may not get wet, but die if a baseball size hailstone hits ya on yer noggins.) Hanging warning tape along the work area may be appropriate if simple verbal instruction during the safety review of the task, with those who will perform it, would judged to be insufficient.

 

[RJohnsonMasterElectrician]

I went on a fire call to downed lines and they looked insulated but was informed by linemen that there was tiny holes in the insulation. Thats how it was made. So I don't beleive overhead high voltage wires are totally insulated.

For every one thousand volts electricity will jump 1/4 inch under normal / dry conditions. If its damp, wet, humid out that distance will grow.

 

[Doug S.]

Blankets? The only time I've seen blankets overhead are within a few feet of a pole, and a linemen overhead...

I've seen yellow or red warning tape plenty of times. Also signs directly below the overheads basically saying "hey dummy look up".

Besides the weight concerns of blankets, as well as not really protecting anything, I would have concern about wind drag.

Maybe you could offer a clothes line for the blankets, and warning tape on the MV line? :grin:


My 2?
Doug S.

 

[jim dungar]

If the OH lines are truly "concentric neutral", they are insulated. I find it strange that CN cables would be hung from a messenger wire. Sounds like this must be for crossing a small roadway.

What kind of work are you doing near them? How close is near?

My thought is, if a employee needs to ask how to determine the correct PPE level, they are not qualified to perform the work (per the 70E definition).

 

[wawireguy]

NFPA 70E has a section about insulated and non-insulated energized parts. Seemed to say that even if you have insulated cables in the voltage range you're looking at you cannot work safely near them without proper arc flash and safety gear along with being a qualified person.

 

[cornbread]

I have pipe fitters that will be working approx 4 ft away. They will be welding and grinding, they are the ones requesting the insualting blankets.

 

[Pierre C Belarge]

Our POCO sent out a letter not too long ago, maybe last year, telling us no work/construction is to take place within 10 feet of their lines. If there was an issue, they want to be notified in writing. They will then send a representative to assess the situation.

 

[cornbread]

On un-insulated lines I agree.

 

[cornbread]

NFPA 70E has a section about insulated and non-insulated energized parts. Seemed to say that even if you have insulated cables in the voltage range you're looking at you cannot work safely near them without proper arc flash and safety gear along with being a qualified person.

Agreed PPE is required,but to what extent. The main hazard I see is the cable cracking and shorting to the neutral..so do I concern myself with the Arc Flash potential from the ground faulut only? I can not hardly see any way where we could have a phase to phase?

 

[charlie]

Kill the line!

Kill the line!

I have been following this thread and wondering why the consternation about the acceptable clearance or covering the line? When we receive a request to put line hoses on the overhead conductors, we will routinely turn down the request. We have found that people, especially crane operators, assume the line is safe since it is covered up. Additionally, the extra weight will cause the line to sag and possibly cause problems with clearances to the underlying conductors (neutral, communications, etc.)

If there is a problem with clearance, we will de-energize the line and let the work progress. After completion, we will inspect the line for damage in the work area, repair if needed, re-energize, and bill the labor for the required switching. I suggest you do likewise.

 

[cornbread]

Appreciate the replies. I plan on bringing this up at our next safety meeting and hopefully get the powers to be to rethink what we are doing.

 

[Fulthrotl]

If there is a problem with clearance, we will de-energize the line and let the work progress. After completion, we will inspect the line for damage in the work area, repair if needed, re-energize, and bill the labor for the required switching. I suggest you do likewise.

yeah, what he said.... :smile:

LADWP will only down a service to make working in proximity safe. no
blankies, booties, mittens or slippers for non DWP personnel.:smile:

the reason being of course liability. if you put a blankie over something
hot, and someone is hurt, guess who "made it safe" for non authorized
personnel... guess who the attorneys walk over with golf shoes?

what we need to do is to wrap the attorneys in safety blankets. the
wire is fine, just don't touch it....