PPE NFPA 70E vs. IEEE1584

[berfman]

I know my situation is not unique, so I was just hoping others could enlighten me on their thoughts and experiences how you are all handling this. I have done my calculations of an existing facility using the EDSA software and after getting the arc flash videos from Brainfiller I can validate the numbers the software comes up with. As I switch the calculations from IEEE to NFPA70E the PPE requirements go up for NFPA and down for IEEE. In fact, NFPA is requiring PPE levels of 3 and 4 on most of the gear, because it is 480 volt switchgear, but IEEE calculations are giving me PPE requirements of level 1 on most of the gear. I know the IEEE calculations are more realistic and I would hate to tell the owner the need PPE 4 gear to perform any live work, if it is not really needed. On that note, if I tell them PPE 1 gear is required, something does happen, and it goes to court, then do I have a legal ground to stand on for choosing the lesser of the two PPE requirements? I am concerned that I choose the PPE 1 requirement, from IEEE, and someone down the road messes with the breaker settings raising the arc flash levels, an incident happens and someone then is injured. How am I to know they messed with the breaker settings unless the breaker is undamaged or their not smart enough to change the breaker settings back, then I have to go to court and argue why I choose the lower PPE level.
I know I can present the information to the owner and see if they prefer to make a decision and then put the legal responsibility on them, but then I feel I am not doing what they hired me for.
So if anyone has any comments on this I would greatly appreciate it.

Thanks,

[brainfiller]

In the legal world it seems like anything can happen even if it does not make sense. << from some of my expert witness work over the years. :eek:

The NFPA method is based on some older equations and you are correct that IEEE is the "latest and greatest" (2002). I think you will find most people, myself included, suggest going with the latest which is IEEE. In court, if it ever came down to that, there could be a whole list of items that could be introduced. I am sure someone could argue that another method - NFPA (which is much older and not based on as much data) gave you "safer??" results. Then you would need to prove that it is the preferred method which I don't think would be that difficult. (but I'm not an attorney and this is not legal advise)

Items that could impact the results also include not only the breaker setting being changed but what about condition and maintenance of the power system? NFPA 70E 205.3 requires that "Overcurrent protective devices shall be maintained in accordance with the manufacturers' instructions or industry consensus standards." If the devices are not maintained will they operate as quickly as their time current curve indicates?

What was the actual utility fault current at the time? Did the utility perform any switching? How accurate was the short circuit data etc. The list goes on and on.

You are facing the situation that many also face - "Second guessing yourself" With so many "what ifs" it is easy to get lost in the "what if" situation.

The big thing to remember is to also emphasise working electrically safe.

[SchlageD]

Could someone explain in what circumstances does IEEE 1864 cap the interruption times at 2 seconds ?

Also being new to the forum, is it OK to use the IEEE 1864 working distances for switchgear? my company has thousands of 5/15kV breakers.

[berfman]

I am by no means an expert on this topic as I am still trying to learn it, so please wait for additional answers from people that have more experience. That being said, it is my understanding that the IEEE 1584 committee continues with testing and developing the equations to try to predict the unpredictable. They have come to realize that their equations miss the mark in some situations, or should I say do not capture the correct incident magnitude. So, there has been some talk about forcing the maximum trip times to between 2 and 10 seconds in order to lower the incident energy. The reasoning behind this, is if an arc flash occurs, someone is not going to stand around in front of the arc flash for the duration of the event, they will get out of the way, which is why there has been talk about limiting the trip times to 2 seconds. Now the disclaimers, first off this is going to be a judgment call by the person doing the arc flash analysis. If you feel the person has access to get away from the arc flash, then may they can reduce the trip times to lower the incident energy calculation, but if you feel a person cannot get away from an incident quickly, then you may just want to go with the breaker trip times.
In my situation, I am using the 2-second guideline, because I have a low level arcing fault of around 6,000 amps, so the upstream breaker does not trip for almost 30 seconds, which leaves me with an incident energy of several hundred cal/cm^2. I feel any incident at this current will not create a situation where the blast will be dangerous and potentially knock someone down or out and the area is open around the equipment, so a person could easily vacate the area.
As some has suggested if you’re in an enclosed area and cannot easily escape, say a bucket truck, then you would not want to limit the clearing time any.
Hopefully that helps you until someone with more authority can correct me or fill in the missing holes.

[berfman]

as far as using the IEEE 1584 working distances for your equipment, I believe you should as long as it meets the requirements of IEEE 1584 which is something like the short circuit current has to be inbetween 700 amps and 106,000 amps. Again please wait for more experience people to respond as I am still learning this.

[brainfiller]

Could someone explain in what circumstances does IEEE 1864 cap the interruption times at 2 seconds ?

Also being new to the forum, is it OK to use the IEEE 1864 working distances for switchgear? my company has thousands of 5/15kV breakers.

The 2 second rule is more about reaction time than anything else. The assumption is within 2 seconds you will either jump back or be blown back, conditions and space permitting. Similar to the "2 second rule many of us learned in driver's education" (except someone younger told me it is now 3 seconds in driver's ed)

As far as new testing, many new areas are being looked at. Arc sustainability is a big one, i.e. configurations, voltages and current levels where an arc flash would self extinguish. DC arc flash, 208 volt arc flash and lots more. As more information becomes available, I "leak" it here as many people have seen.

[mike01]

whenever we see an RFP for an arc-flash study or provide it in our specifications it is always a clarification by the client (most of the time we find if the client is asking for an arc flash label beyond the code min. they know the ansewer). if the client ask's for a professional opinion we would recommend 1584, but if they want to we can discuss the differences and our professional opinions. like brainfiller stated having a safety plan or training is the best defense other than the "don't work on it live" statement. It is also intresting hearing about all the upcomming and testing being done as part of the 1584 study please leak........