I need to move an energized 500 MCM 480 volt cable. What type of PPE do I need? I'm looking at NFPA 70E an I think since the copper is not exposed that no PPE is needed. In my pee brain I think we should wear PPE rated for an Arc Flash should it occure. FYI.... calcs come out as cat 2 hazard. Any advice or info would be grreatly apprecaited.
480 Volt cable move
- Thread starter cornbread
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zog
Senior Member
- Location
- Charlotte, NC
Why do you have to move live cables? Cant see anyway to justify this work. NFPA 70E Article 110.8(1) states:
"Live parts to which an employee might be exposed shall be put into an electrically safe work condition before an employee works on or near them, unless work can be justified according to 130.1
130.1 says "Live parts to which an employee might be exposed shall be put into an electrically safe work condition before an employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. Energized parts that operate at less than 50 volts to ground are not required to be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.
NOTE 1: Examples of increased or additional hazards include, but are not limited to, interruption of life support equipment, deactivation of emergency alarm systems, and shutdown of hazardous location ventilation equipment.
NOTE 2: Examples of work that may be performed on or near exposed energized electrical conductors or circuit parts because of infeasibility due to equipment design or operational limitations include performing diagnostics and testing (e.g., start-up or troubleshooting) of electric circuits that can only be performed with the circuit energized and work on circuits that form an integral part of a continuous process that would otherwise need to be completely shut down in order to permit work on one circuit or piece of equipment.
Also odds are your arc flash analysis dosent apply here, it was done assuming a working distance of at least 18", that distance is where the Ei was calulated and PPE requirements determined. If you are moving these cables you are probally closer than 18", you are touching them.
Example lets say you had a HRC 2 condition, 20cal/cm2 at 18", at 12" that becomes 44.5 Cal/cm2 (No PPE can protect you from that), at 6" it is 172Cal/cm2, and at 1" it is 5783Cal/cm2!
"Live parts to which an employee might be exposed shall be put into an electrically safe work condition before an employee works on or near them, unless work can be justified according to 130.1
130.1 says "Live parts to which an employee might be exposed shall be put into an electrically safe work condition before an employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. Energized parts that operate at less than 50 volts to ground are not required to be deenergized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.
NOTE 1: Examples of increased or additional hazards include, but are not limited to, interruption of life support equipment, deactivation of emergency alarm systems, and shutdown of hazardous location ventilation equipment.
NOTE 2: Examples of work that may be performed on or near exposed energized electrical conductors or circuit parts because of infeasibility due to equipment design or operational limitations include performing diagnostics and testing (e.g., start-up or troubleshooting) of electric circuits that can only be performed with the circuit energized and work on circuits that form an integral part of a continuous process that would otherwise need to be completely shut down in order to permit work on one circuit or piece of equipment.
Also odds are your arc flash analysis dosent apply here, it was done assuming a working distance of at least 18", that distance is where the Ei was calulated and PPE requirements determined. If you are moving these cables you are probally closer than 18", you are touching them.
Example lets say you had a HRC 2 condition, 20cal/cm2 at 18", at 12" that becomes 44.5 Cal/cm2 (No PPE can protect you from that), at 6" it is 172Cal/cm2, and at 1" it is 5783Cal/cm2!
We are a chemical plant and feeder is for an continuous process, shuting down and starting up thep process is indeed more dangerous than moving the energized cable.
Your point of the proximity to cable is well taken, I have ask the engineer to look at the breaker settings and see what the Arc Flash would be if we dial down the instanenous setting. By lowering the setting we get down to a Cat 0
Your point of the proximity to cable is well taken, I have ask the engineer to look at the breaker settings and see what the Arc Flash would be if we dial down the instanenous setting. By lowering the setting we get down to a Cat 0
peter d
Senior Member
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- New England
cornbread said:
This doesn't make sense to me. If you lower the trip setting, and in the process of moving this cable cause a short or ground fault and trip the breaker, won't you cause this process to stop and possibly "run away?" It sounds to me like a shutdown makes more sense than risking an accidental shutdown by working it live.
zog
Senior Member
- Location
- Charlotte, NC
Dont confuse "Infeasable" with "Inconveinent". Chemical plants do shutdowns too, I have worked on plenty of them myself.
What are you really doing? Are you just moving around a cable in a tray or similar task or are you disconnectiong, moving, and reconnecting the cable? I hope you answer the former.
What are you really doing? Are you just moving around a cable in a tray or similar task or are you disconnectiong, moving, and reconnecting the cable? I hope you answer the former.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
cornbread said:
Do you mean move an insulated cable from one physical location to another, like from one side of a cable tray to a the other?
Or, do you mean disconnect the cable from its live terminations, move the energized cable, and then re-terminate it?
zog
Senior Member
- Location
- Charlotte, NC
Isnt that the exact same question I asked him Jim?
Thats a key piece of info here isnt it?
Thats a key piece of info here isnt it?
electricalperson
Senior Member
- Location
- massachusetts
this job sounds pretty dangerous
izak
Senior Member
- Location
- Springfield, MO
To my mind, if he was going to disconnect it, there wouldnt be any reason to not turn it off..
electricalperson
Senior Member
- Location
- massachusetts
if iwas doing it i would schedual a shut down to do it safely. what kind of dangers can happen when a chemical plant gets shut down and everything is coordinated?
chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
electricalperson said:
Gas prices go up.
HighWirey
Senior Member
- Location
- Cocoa, Florida, USA
cornbread said:
Dear Mr cornbread,
Years ago, in my youth, I would have attempted your 'hot wire moving' task. Now that I am a lot older, and a tiny bit wiser, I understand that I could not cover myself in enough PPE to perform that stunt.
You stated "starting up thep process is indeed more dangerous than moving the energized cable".
More dangerous for whom, those 'bottom line chemical plant board member$' who 'said' you could not have an outage for that work?
I can visualize those plant e-mails wizzing around the day after the catastrophe: "Something happened on the floor yesterday and we will lose three days of production, and somebody got hurt".
What about that somebody, poor ole Mr cornbread?
If that engineer is your boss, tell him to rustle up a little sand, and pack it where 'ole Sol don't shine.
And do you know what? I'll bet you will still have your job tomorrow.
If there was ever a work environment that would never allow any type of outage it was in my orbit. As an individual, and later as an EC, those boardroom men eventually understood that their coffee pot was going to be stilled for a while.
I was always thankfull to return home every evening, without that short stop at the morgue . . .
We can quote kil/cals per nanonarn, watts per second, joules, rules, regs and dilethium crystals ad infinitum, till our calculator batteys pass. We are still putting our lives in 'harms way', just like our poor troups . . .
Sorry for the graphic rant folks, but this is serious stuff.
Best Wishes Everyone
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
zog said:
Sometimes I don't read every posting before replying.
But it looks like we may never know.
If this is a insulated cable. Some type of large SO? I don't see a problem. I'd visually inspect the cable for insulation damage. I'd wear gloves and move that thing. If it was 4160 that would be a different matter but we are talking 277 volts per leg. Do you people get afraid when you have to change a ballast live in a 277 light? I don't reccomend it but everyone does it once in a while. How about pulling out some live wires in a j-box to look at them. That insulation is a heck of a lot less that what would be on a large SO cable.
electricalperson
Senior Member
- Location
- massachusetts
oh then in that case by all means risk your life! :grin:chris kennedy said:
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Pulling them out while energized is relatively easy; stuffing them back in while hot can be a harrowing experience. There might be an insulation nick from the original install that you find the hard way, or caused by a sharp edge on a plaster ring.wireman71 said:
You might disturb a less-than-perfect connection that was working, until you jostled it. If a scheduled shutdown of the equipment can't be tolerated, then what about an unscheduled one, where the wrong piece of equipment may shut down first?
zog
Senior Member
- Location
- Charlotte, NC
wireman71 said:
There is a big difference in fault current on a 480V feeder cable and a ballast or Jbox due to the impedances, not to mention the ac flash hazard.
zog
Senior Member
- Location
- Charlotte, NC
HighWirey said:
Rant approved. I tried proving to him with calcs that PPE cant protect hom and gave him the requirements in 70E to do such task but he still thinks (Or rather, I am guessing, has been brainwashed) to believe this live work is somehow allowed because shuting down a chemical process is not convienent.
mattsilkwood
Senior Member
- Location
- missouri
its more convenient to schedule a shutdown than to take time out of my busy day to attend my funeral.
- Location
- Massachusetts
At this point, without more input from the OP it is ridiculous to speculate.
As far as we know these may be 480 volt flexible cords being moved.
As far as we know these may be 480 volt flexible cords being moved.
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