Manholes

tkb

Senior Member
Location
MA
When working in a manhole that has live 15kv cables, does the worker have to wear arc flash gear?

This is a complex that has multiple feeders in duct banks branching to several buildings.
We will be pulling another circuit through spare ducts through several manholes to the power plant. There are no elbows, switches or exposed parts, just cable and splices on racks.
 

bure961

Senior Member
Location
Farmingham, MA
YES , And de energise it before working on it. For one thing workers will be in a confined space that usually contains water. Duc banks have other cables that could be sizzling from bad connections. Need shock protection atleast. Just my opinion but should be in 70e plus Osha would have something to say.
 

tkb

Senior Member
Location
MA
YES , And de energise it before working on it. For one thing workers will be in a confined space that usually contains water. Duc banks have other cables that could be sizzling from bad connections. Need shock protection atleast. Just my opinion but should be in 70e plus Osha would have something to say.
So we should shut down the complex for a month and send 1000 workers home while we work in 20 manholes over a 3/4 mile distance while we do our work?
That is not going to happen. There are multiple circuits in this system branching to several buildings.

This type of work is done every day by the utility company and electrical contractors.

Your opinion is fine, but I am looking for what is required by OSHA. Working is a manhole with a 40cal suit doesn't seem practical. There are no live parts exposed, no elbows or switches in these manholes. Only cables and splices on racks.

I have done this type of work years ago and we never used any special protection besides the normal confined space equipment.

I want to make sure we are working in a safe and OSHA compliant manner today.
 

wbdvt

Senior Member
Location
Rutland, VT, USA
Occupation
Electrical Engineer, PE
I believe that for this type of work OSHA would consider this "utility type work" and you would fall under the OSHA utility standards in 1910.269. This might even be considered construction work by OSHA so then you would be under the 1926 standards.

To the best of my knowledge there has been no testing on the affects of an arc flash event inside a manhole. One concern is that there will be a lot of energy that is reflected off the surfaces beside and behind you. The published testing so far has been for open air or box type events. The box type is where you are standing in front of a panel/MCC cubicle/padmount transformer etc.

As a minimum, I believe OSHA would want you do a risk analysis of the task to determine the hazards and how to protect from them.
 

mayanees

Senior Member
Location
Westminster, MD
manhole live work

manhole live work

I advise that you determine the incident energy level on the cable inside the manhole, as if the cables were terminated on a busbar, then wear the appropriate PPE.
At 15kV, it is likely that the incident energy level is under 8 calories, then a PPE 2 suit protects against any arc-flash occurrence.
A Risk Analysis could show that an arc-flash event is unlikely. But you should still be comfortable that if a cable in the manhole is nicked, and comes into contact such that an event occurs, you're still protected.
 

jtinge

Senior Member
Location
Hampton, VA
I would also suggest you post this question on arcflashforum.com. They have many industry experts that are up to speed on current NFPA 70E and OSHA electrical work practice requirements regarding arc flash. I know manhole work has been discussed and you may find a forum post that may answer your question. Realize, as what mentioned earlier, that work requirements for systems covered by NFPA 70E and for those done by utilities may differ. The need for arc flash PPE will be determined by the results of a risk assessment of the tasks you intend to perform. The latest version of NFPA 70E has separated the assessment of the need for PPE from the calculation of the type of PPE based on available incident energy level.
 

Fulthrotl

~~Please excuse the mess. Sig under construction~~
When working in a manhole that has live 15kv cables, does the worker have to wear arc flash gear?

This is a complex that has multiple feeders in duct banks branching to several buildings.
We will be pulling another circuit through spare ducts through several manholes to the power plant. There are no elbows, switches or exposed parts, just cable and splices on racks.
it was 2005 when i worked for them, but LADWP has a lot of 34.5 stuff KV
pulled thru underground substructures, along with 5 KV.

now, rules may change, but then it was common to enter in normal FR clothing,
after pumping the vault out, and dropping a sniffer.

having a vault filled with water is usually a pretty good test of cable integrity.
usually, if we were pulling thru a vault, we'd rig sheaves, and nobody would
be in the vaults during the pull.

i'll make a couple calls to friends who are there, and current on best practices,
and post what they say.
 
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