It is currently Thu May 28, 2020 5:02 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Verifying 0 energy in a panel with dangerous rating
PostPosted: Fri Oct 05, 2012 6:58 am 

Joined: Thu Nov 03, 2011 8:28 am
Posts: 2
How would a qualified person verify O voltage in a panel if the rating label read Dangerous No safe PPE exists. I must be missing something here. If you cannot enter the equipment, how would you check.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Oct 05, 2012 8:11 pm 
Sparks Level

Joined: Mon Mar 29, 2010 5:02 am
Posts: 136
If there was a to visibily make sure the source was opened - i.e utility fuses, visible disconnect on the supply. If the Single Line is up to date and accurate...

An external point to meter voltage at, such as a separate junction box that is fed from the equipment with the high rating, but has a 5 amp breaker/fuse or less feeding it and is able to locked and opened for testing only..

Just a couple of thoughts...


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Sat Oct 06, 2012 6:03 am 
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
Read the definition of arc flash hazard. If the activities required to verify absence of voltage are not likely to trigger an arc flash, then you can do those.

For instance is the equipment known to be in good working order and not faulted in some way or is the nature of the fault such that the location where you are testing for absence of voltage known to be in good working order? Is opening the disconnect likely to result in an arc flash hazard? Is opening the door likely to result in an arc flash hazard? Is using a meter with the tip protectors on so that there is not enough exposed conductive surface to cause a phase-to-phase or phase-to-ground fault ikely to cause an arc flash hazard?

Generally except for the first question your answers are likely to be that the risk is remote. One glaring exception is draw out switchgear which has a higher likelihood of failures than others, and many of the additional fault causes likely result in arcing faults.

If you can't go there, then as stated earlier, you go upstream or downstream and do your LOTO and/or test for absence of voltage there first, usually preferably upstream.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Oct 08, 2012 5:59 am 
Sparks Level
User avatar

Joined: Mon Nov 23, 2009 6:37 am
Posts: 51
Location: Tampa, FL
You can use a tic tracer attached to a hv test stick, thereby increasing the distance between you and the equipment you are testing and also lowing the available fault current at your location. You can recalculate the IE at the distance of the test stick, eg. 6', 10', etc and it may be low enough to use PPE to establish absence of potential.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Oct 08, 2012 7:41 am 

Joined: Thu Feb 04, 2010 5:00 pm
Posts: 36
Location: Camp hill Pa
One Can verify the voltage by being outside the Arc flash Boundary and then using Hot Sticks of appropriate length with a meter or other device on the far end to measure the voltage or see if it is zero. It is advisable to wear protective gloves and sleeves. this is how the utility workers do it. after assuring that the voltage is zero, protective grounds can then be installed. see the video that was placed on the forum by AB Chance and the lineman's and cableman's handbook. Have someone demonstrate how to do this.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Oct 08, 2012 5:45 pm 
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
JayWes38 wrote:
One Can verify the voltage by being outside the Arc flash Boundary and then using Hot Sticks of appropriate length with a meter or other device on the far end to measure the voltage or see if it is zero. It is advisable to wear protective gloves and sleeves. this is how the utility workers do it. after assuring that the voltage is zero, protective grounds can then be installed. see the video that was placed on the forum by AB Chance and the lineman's and cableman's handbook. Have someone demonstrate how to do this.


Only works for 1 kV or higher. Tics are known to have issues below that point and the accepted test methods are voltmeters, voltmeters, and voltmeters.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Tue Oct 09, 2012 7:59 am 
Sparks Level

Joined: Tue Apr 03, 2012 1:28 pm
Posts: 53
Location: Louisville KY
Also, the requirement is to verify no voltage phase to phase and phase to ground...a tic tracer does not do this. (70E 120.1 (5))


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Mar 14, 2013 7:07 am 

Joined: Tue Jun 12, 2012 11:45 am
Posts: 17
To your first statement of no safe PPE exists. I've found that engineering stops the evaluation if the ICE is >40 cal/cm2. This is an artificial ceiling and it is not restricted to have PPE levels greater than this value. If this has happened, then this needs to be re-evaluated, even if the PPE level required is above 40 cal/cm2.

The next component is the risk assessment. Depending on the work activity, of which verifying voltage could reduce the level of PPE if analyzed properly. In most cases the engineer performing the calculation has given the worst case activity scenario therefore increasing the PPE level unnecessarily.

The third option is to recalculate the Incident energy level (IEL) with a greater working distance (WD). By increasing this WD, the IEL level will be reduced. This distance should be extended to where the activity is still practical.

A fourth option is to utilize maintenance settings on the protective relay feeding this device. Much of the new solid state relay devices have the capability of having multiple settings. The opportunity would be to have faster, more sensitive tripping settings to reduce the ICE and PPE levels

Let’s be clear; the arc flash boundary does not change under any circumstances unless either the fault current or interrupting time has been reduced. As we all know the AFB is the point at which the qualified work must where the IEL is <1.2 cal/cm2. The task does not change this value.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Mar 14, 2013 5:08 pm 
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
VinnyAces wrote:

Let’s be clear; the arc flash boundary does not change under any circumstances unless either the fault current or interrupting time has been reduced. As we all know the AFB is the point at which the qualified work must where the IEL is <1.2 cal/cm2. The task does not change this value.


An arc flash hazard exists provided that the activity is interacting with the equipment in such a manner where it is likely to cause an arc flash hazard. Just walking by doesn't count. See numerous ROP's and 70E itself, such as the definition of an arc flash hazard. In other words, electrical equipment is not "inherently dangerous" but depends on the condition and the task.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Mar 15, 2013 4:39 am 

Joined: Tue Jun 12, 2012 11:45 am
Posts: 17
I wouldn’t disagree with that statement at all, however the context of the question was voltage verification. Based upon the OSHA interpretation, I read that this activity must be treated as energized until proven otherwise (which is being accomplished by this step). Therefore the PPE requirements for the working distance and arc flash boundary would be imposed.

On another tangent; I would challenge the wording though on "activity is interacting". This gets us back to our other discussion on risk. There's a probability of failure of all equipment from breakers failing, due to wear, over current, operator caused mal-operation, etc. Also, much electrical equipment is remotely or automatically operated without the persons in vicinity knowledge. There is little difference in my perception of the worker pushing a start button, or the equipment auto starting based upon a remote automatic command other than the proximity that the worker may be to the device.

It's also fairly logical that it is statistically less likely for a lighting panel to spontaneously fail with no worker interaction vs. the potential for arc flash to occur while doing work on live equipment. But to this point, the hazards are always there.

When the NFPA places requirements as " reading a panel meter while operating a switch “and "starter operation with doors closed" as a cat 0 to the worker, this forces the arc flash boundary to be established, and the PPE requirements inside to be maintained. So if there's a facility that has much of the process equipment starting and stopping based upon automatic functions what’s the difference to an individual passing through the arc flash boundary when a worker starts the equipment vs. a field instrument starting the equipment.

I don’t see any discussion about reduction of the arc flash boundary distance based upon risk assessment.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Mar 15, 2013 4:50 am 

Joined: Thu Mar 19, 2009 9:40 am
Posts: 19
Location: Wi
We will also go to the line side of the next downsream device to verify no voltage before opening the higher rated device as part of our safety program.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Mar 15, 2013 5:05 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 524
A fused meter test point? Assuming the fuse would even reduce the IE to non-Dangerous levels, after verification you would next need to check upstream of the fuses to ensure they were still intact. But that's the location you needed to test in the first place, so the hazzard is not avoided.

I agree you should let your PPE values go higher than 40, but for absense of potential testing purposes only.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Sat Mar 16, 2013 6:08 am 
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
VinnyAces wrote:
I wouldn’t disagree with that statement at all, however the context of the question was voltage verification. Based upon the OSHA interpretation, I read that this activity must be treated as energized until proven otherwise (which is being accomplished by this step). Therefore the PPE requirements for the working distance and arc flash boundary would be imposed.


You can't make that leap. Just because it is energized does not automatically mean that there is a shock or arc flash risk. Risk meaning that there is a hazard present that is likely to result in injury. For instance even though capacitive taps on energized MV equipment are energized, the ones on shielded power cable do not pose a significant shock hazard. Touching a voltage detector to a capacitive tap on an elbow connector (IEEE 386 type) would not cause an arc flash. So this is an example of up to 35 kv equipment where testing for absence of voltage definitely can be done without any special PPE. I don't really care what the sticker says because it assumes that one is interacting with the equipment in such a manner that it could cause an arc flash or (if the label has shock information) a shock.


Quote:
On another tangent; I would challenge the wording though on "activity is interacting". This gets us back to our other discussion on risk. There's a probability of failure of all equipment from breakers failing, due to wear, over current, operator caused mal-operation, etc.


I did not at any time suggest that there is zero probability of an arcing fault even when just walking by. There is a nonzero chance of a meteor strike while walking across the parking lot. We do not require meteor shields at least terrestrially because the likelihood is low.

Unlike mechanical equipment, electrical equipment failure modes tend to be random, no matter what the cause. As a result periodic inspection and maintenance is required in order to determine equipment condition. Molded case breakers require visual inspection after every trip (NEMA AB-4), as well as annual visual inspection and testing every 3 years. Other types require testing, inspection, and lubrication maintenance every 3-8 years. If not using modern fluoro based lubricants, annual exercising is also required to redistribute the lubricant.

If following proper maintenance procedures (article 200 of 70E requires this and refers to 70B) then the probability of an arcing fault is remote as per 70E definition of arc flash provided for instance that voltage testing uses noncontact voltage detection above 1kv or a multimeter with probes insulated against both phase-to-phase and phase-to-ground faults and the meter is inspected before use for damage or contamination on the insulation or to the meter itself.

Quote:
Also, much electrical equipment is remotely or automatically operated without the persons in vicinity knowledge. There is little difference in my perception of the worker pushing a start button, or the equipment auto starting based upon a remote automatic command other than the proximity that the worker may be to the device.


There is a huge difference. Power must be removed, locks applied, and controls must be tested (try) before testing for absence of voltage. This would be grounds for severe disciplinary action at most sites, whether the system is remotely controlled or not.


Quote:
It's also fairly logical that it is statistically less likely for a lighting panel to spontaneously fail with no worker interaction vs. the potential for arc flash to occur while doing work on live equipment. But to this point, the hazards are always there.


Protecting against ALL hazards, even unlikely ones, is impossible. I have all the time in the world to address credible risks but don't waste time and resources on incredible ones. Yesterday we spent an hour unwinding an incredible risk my predecessor did. There was a concern about a fan that failed catastrophically. It was one of 12. My predecessor put a big vibration shutoff system in. The trouble was that it worked when the fan flew apart during the first incident but because the event was catastrophic, it did not prevent the hazard. An analysis of the probability of personnel being in the line of fire showed that this is an incredible event. In addition we recognized that even if it was credible, we'd need concrete shrouds like they use for destructive testing of jet engines.

Quote:
Quote:
When the NFPA places requirements as " reading a panel meter while operating a switch “and "starter operation with doors closed" as a cat 0 to the worker, this forces the arc flash boundary to be established,and the PPE requirements inside to be maintained.


The text that refers to the table is clear that this table only applies if you have not done your own arc flash hazard assessment. You can't mix and match. The interacting question comes up before the table if using the table method.

Quote:
So if there's a facility that has much of the process equipment starting and stopping based upon automatic functions what’s the difference to an individual passing through the arc flash boundary when a worker starts the equipment vs. a field instrument starting the equipment.
Quote:

I don’t see any discussion about reduction of the arc flash boundary distance based upon risk assessment.


The table specifically states that a risk assessment (not just a hazard assessment) was done and the values were reduced by 1, 2, or 3 values. However I have a big issue with the methodology. 1584 states that there is a 90% likelihood of avoiding second degree or greater burns if wearing PPE rated according to the calculation in 1584. No probabilities are given below that threshold, and published test results used to determine ATPV seem to suggest that the probability goes to zero usually about 1 cal below the ATPV, and it changes from one material to the next so there is no such thing as a "standard" curve. What the risk analysis did is to reduce PPE based on a hazard reduction. But in almost all cases the likelihood is reduced, not the hazard. The table should say either "no" for arc flash PPE or give the same rating, meaning that either adequate PPE is required (matching the incident energy) or not. PPE reductions should be taken only for equipment design changes (arc resistant gear with doors closed) or increases to working distance. For instance arc resistant gear testing ensures that an arc flash will not burn through 4 ounce cotton. A burn from synthetic fibers is still possible.

If we followed what you are suggesting the consumer product safety commission would be pulling residential lighting panels off the market, and we'd be putting meteor shields over all work sites, to say nothing of all buildings, roadways, and parking lots. We'd also ban all moving vehicles, and 5 gallon buckets.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 13 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
© 2019 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883