# Arc Flash Study



## Almost Retired (Sep 14, 2021)

the mill i worked at sent all of us to arc flash school and never did a study on the mill
we had 13.8kV to 480V transformers on the mill property

i have often wondered what all could have gotten us
but i never expected low voltage to be one of them
i have always ASS U ME d that because it went through so many transformers it couldnt possibly be dangerous
because the impedance of the transformers would naturally limit the fault current

your study and several threads on here have taught me otherwise


----------



## mburtis (Sep 1, 2018)

Highest we have is 21 I think, but that is on a 240v ungrounded mcc. A lot of the 480 stuff is way way less.


----------



## Flashedout (4 mo ago)

I have seen studies in the past that ended up placing equipment over the 40cal .. After doing some investigation on the study itself.. the Contractor that performed the study did a bear minimum study..where they took pictures of the nameplates and punched in some numbers into the software and printed out the labels.. Once I found out they didn't even determine available fault current coming into the facility.. I knew something wasn't right.
The single line diagrams didn't have any AFC or even distance of distribution conductors.. 
They simply took pictures of the nameplates in the substation and printed off really high incident energy warning labels..
I finally performed a much more comprehensive study with the proper values and full impedance charts (wire distance and size, CB trip curves, etc) along with available fault currents from the utility.. come to find out the equipment in this particular sub station was in the 12cal/cm² which placed the HRC in a much more manageable Risk factor...
The bottom line was the original engineering company was placing the employee's at a higher risk being overly dressed in PPE ...
They figured if the risk is high enough nothing would come back on them..not caring about the complication it's causing for the everyday sparky.. 
To add when over looking the policy alot of the guidelines was outside of the IEEE 1584 or NFPA..
I take Arc flash hazards very serious and also understand the dangers of being overly dressed when performing simple tasks.. It's a shame to see a firm not perform what they are hired to do..
The company is now in the process of filing a suit against the firm.. Once the papers come out I wanted to share with the community to see what everyone thinks of this mess...


----------



## canbug (Dec 31, 2015)

I know what you're saying, I've walked around with an engineer that didn't give me any confidence in his report. 
This one is a different kettle of fish.
All the curves, all the single lines and more information than I'll go through, that's for the GM. It was done by Schneider and very thorough. 

Tim.


----------



## kb1jb1 (Nov 11, 2017)

Flashedout said:


> I have seen studies in the past that ended up placing equipment over the 40cal .. After doing some investigation on the study itself.. the Contractor that performed the study did a bear minimum study..where they took pictures of the nameplates and punched in some numbers into the software and printed out the labels.. Once I found out they didn't even determine available fault current coming into the facility.. I knew something wasn't right.
> The single line diagrams didn't have any AFC or even distance of distribution conductors..
> They simply took pictures of the nameplates in the substation and printed off really high incident energy warning labels..
> I finally performed a much more comprehensive study with the proper values and full impedance charts (wire distance and size, CB trip curves, etc) along with available fault currents from the utility.. come to find out the equipment in this particular sub station was in the 12cal/cm² which placed the HRC in a much more manageable Risk factor...
> ...


I bet your example is very common. These studies are very expensive but how accurate are they? The plant I worked at had a study done and a third of the distribution was left off the line diagram. There were generators and transformers listed that were non existant. Feeder sizes and lengths were wrong. Guess who got a talking to for bringing out the errors and omissions? I quit shortly after.


----------



## MikeFL (Apr 16, 2016)

canbug said:


> We just had a very large arc flash study and report about our Domestic and International Terminal. We have two 25KV and two 13.8KV feeds into the building, distribution down to 600v and then down to 120/208v.
> Where incident energy exceeds 40cal/cm2 and operators cannot wear suitably rated PPE, we are to use the remote operators (SCADA/Remote Racking) or switch from upstream.
> The highlight of the report is the following.
> 
> ...


If you want to make brownie points, make sure those above you know you are grateful for the organization taking the time, effort and expense to ensure a safe work environment for you and for your workforce.


----------



## micromind (Aug 11, 2007)

I sincerely hope that some of these educated idiots find themselves is serious trouble for overestimating the hazard. They are being paid (usually a lot.....) for producing an accurate study, not some sort of inflated guess because they want no liability for underguessing...........


----------



## Flashedout (4 mo ago)

kb1jb1 said:


> I bet your example is very common. These studies are very expensive but how accurate are they? The plant I worked at had a study done and a third of the distribution was left off the line diagram. There were generators and transformers listed that were non existant. Feeder sizes and lengths were wrong. Guess who got a talking to for bringing out the errors and omissions? I quit shortly after.


Your right these studies can get very expensive, Iam also willing to believe this is alot more common than we would like it to be. I know in Pennsylvania they do not require you to submit your raw data regarding the study, so regulation is very minimal, they pretty much require the end results and however it gets there, it just does.. policy, proper labeling. Is enough to appease the regulation. It's pretty sad some firms are sitting on their yacht and not really thinking about the poor sparky In a spaceman outfit trying to change a breaker in a 40A sub panel..(exaggerated) because they thought it was ok to place a >40cal/cm² label..just to save their tail.

I do believe if the study is preform correctly it's worth it's weight in gold.. the amount of data analysis you can gain also the dangers that's are unseen knowing what type of energy the equipment has is priceless.. But the big wigs sometime get blinded by $$ and forget the big picture the *electrician safety, *
Do what you have to, just to meet the federal guidelines and get out...
Just imagine calling the inspector for the first time (Hey bud, the work is done just don't open the panel) 😆

I don't mean offense to the engineers that do perform, In fact I would like to compliment them because it takes alot of data and careful analysis to get the numbers right.. When they are right, I appreciate the concern to our safety!


----------



## SWDweller (Dec 9, 2020)

I am all for an Arc Flash Study, done correctly then the labels go up. Hand in hand a Coordination Study needs to be done as well. I have done several of both. Bottom line a Coordination Study and fixing the issues can lower the Arc Flash at a given location. Yes in places we had to change Breaker trip units and CT's. There are several replacement device MFG's out there that can be adapted to most MV and large frame LV breakers. 

I had an engineer at Eaton that used to call me and get his jobs on my schedule. The grunt work collecting the data is far from fun. I asked once why he picked on me so much, He said your data makes sense and I do not have to guess. Might be my anal attitude about identifying everything.

The real sad part as far as I know if you change the distribution after the studies are done you have garbage again.


----------



## kb1jb1 (Nov 11, 2017)

SWDweller said:


> I am all for an Arc Flash Study, done correctly then the labels go up. Hand in hand a Coordination Study needs to be done as well. I have done several of both. Bottom line a Coordination Study and fixing the issues can lower the Arc Flash at a given location. Yes in places we had to change Breaker trip units and CT's. There are several replacement device MFG's out there that can be adapted to most MV and large frame LV breakers.
> 
> I had an engineer at Eaton that used to call me and get his jobs on my schedule. The grunt work collecting the data is far from fun. I asked once why he picked on me so much, He said your data makes sense and I do not have to guess. Might be my anal attitude about identifying everything.
> 
> The real sad part as far as I know if you change the distribution after the studies are done you have garbage again.


Your last sentence says a lot about these reports.
One panel change or additional feeder then you need a new study.$$$. The plant I was at added a 400 amp feeder and panel to the packaging floor and they wanted it added to the arc flash report. They just had one done and the engineering company wanted another $35,000. To do another study.


----------



## Almost Retired (Sep 14, 2021)

kb1jb1 said:


> Your last sentence says a lot about these reports.
> One panel change or additional feeder then you need a new study.$$$. The plant I was at added a 400 amp feeder and panel to the packaging floor and they wanted it added to the arc flash report. They just had one done and the engineering company wanted another $35,000. To do another study.


time for a new contractor


----------



## kb1jb1 (Nov 11, 2017)

I think it is the insurance companies that are behind the IR and Arc Flash reports. As several others here said it is a box that the company checks off for compliance. Almost like bringing in your car for it's yearly inspection. Are they important? IDK , unless it is for a larger facility with a dedicated qualfied maintenance staff. A bigger problem is when facilities use unqualified people to save money. I have seen maintenance men checking fuses in a bucket not knowing how to open the cover so they use a big screw driver and bent the safety locking mechanism. The next time the bucket was opened the bracket parts fell off into the bucket. Nothing shorted this time but it was a precarious fix.
Also what is the report mainly used for? To select the proper PPE. PPE is the last resort and not the first. It is to be used after the other five are ruled out. Remove the hazard first. Very few facility managers want to shut down panels because of an inconvenience. Too bad.


----------



## Almost Retired (Sep 14, 2021)

SWDweller said:


> I am all for an Arc Flash Study, done correctly then the labels go up. Hand in hand a Coordination Study needs to be done as well. I have done several of both. Bottom line a Coordination Study and fixing the issues can lower the Arc Flash at a given location. Yes in places we had to change Breaker trip units and CT's. There are several replacement device MFG's out there that can be adapted to most MV and large frame LV breakers.
> 
> I had an engineer at Eaton that used to call me and get his jobs on my schedule. The grunt work collecting the data is far from fun. I asked once why he picked on me so much, He said your data makes sense and I do not have to guess. Might be my anal attitude about identifying everything.
> 
> The real sad part as far as I know if you change the distribution after the studies are done you have garbage again.


and yes Coordination needs to be done most definitely
you dont want to trip the main because a lower V feeder circuit was too slow and the main was too fast


----------



## Almost Retired (Sep 14, 2021)

my mill had a situation that one particular 480 distribution main would trip every sat morning (never found out why, but it quit after a cpl years)
mill not running but production super was in to do final reports for the week, and of course it was his office involved


----------



## SWDweller (Dec 9, 2020)

Finding why it shuts off on Saturday is easy, Just put on a recording meter, volts amps, and harmonics run for 4 days before and 2 days after. I would think it would be clear what the problem was. 
When the even stopped were there any personnel changes?

Years of experience chasing ghost/events at the university in Tempe.


----------



## canbug (Dec 31, 2015)

I would first check who worked Fri night.

Tim


----------



## Flashedout (4 mo ago)

Almost Retired said:


> my mill had a situation that one particular 480 distribution main would trip every sat morning (never found out why, but it quit after a cpl years)
> mill not running but production super was in to do final reports for the week, and of course it was his office involved


See even breaker don't like to work on Saturday morning 😆




SWDweller said:


> I am all for an Arc Flash Study, done correctly then the labels go up. Hand in hand a Coordination Study needs to be done as well. I have done several of both. Bottom line a Coordination Study and fixing the issues can lower the Arc Flash at a given location. Yes in places we had to change Breaker trip units and CT's. There are several replacement device MFG's out there that can be adapted to most MV and large frame LV breakers.
> 
> I had an engineer at Eaton that used to call me and get his jobs on my schedule. The grunt work collecting the data is far from fun. I asked once why he picked on me so much, He said your data makes sense and I do not have to guess. Might be my anal attitude about identifying everything.
> 
> The real sad part as far as I know if you change the distribution after the studies are done you have garbage again.


I agree, coordination and Arc flash studies go hand in hand.. As you know the amount of information retained while performing the study will get you very acquainted with your system, if your doing the study yourself. Which can be priceless for the maintenance electrician..
I also had a insistence where a 13.8kv was bought used and installed, it already had a label from the old install and when the inspector came to write it off.. He seen the label and said, Ok Arc flash warning is present ,blah blah. I just looked at our engineer an he shook his head as for me to stay quiet...I later fixed with the proper values and instead of it being a HRC 2 it was a HRC 4 which could have been a problem..
As for changing any equipment with a study performed, it's true you would need another analysis performed, when any impedance change will require a revision..
Yes taking data could become very tedious specially doing it the proper method, The first firm charged my company $290k because it had 27 substations.. and all they did was take pictures of the Nameplates..blew my mind 😳


----------



## canbug (Dec 31, 2015)

We have airside to do but the Terminal was 100k with 10k annual fees to keep it updated.

Tim.


----------



## Almost Retired (Sep 14, 2021)

SWDweller said:


> Finding why it shuts off on Saturday is easy, Just put on a recording meter, volts amps, and harmonics run for 4 days before and 2 days after. I would think it would be clear what the problem was.
> When the even stopped were there any personnel changes?
> 
> Years of experience chasing ghost/events at the university in Tempe.


no such equipment available, it didnt matter that much, there was always an electrician available to reset
according to reports it did it for several yrs before i got there
since it stopped after a cpl years, without a permanent change in personnel
i personally suspected poco was doing something , probably changing a tap due to us being down for sat and sun.

it is all ir-relevant now, i dont work there anymore

just an example of a main tripping without any thing under it tripping


----------

