It is currently Sat Jan 20, 2018 5:31 pm



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Utility refusal to provide service transformer impedance
PostPosted: Tue Jan 02, 2018 12:22 pm 
Offline

Joined: Tue Feb 17, 2009 8:38 am
Posts: 33
Location: Westminster, MD
There is an electrical Utility in Virginia that is taking the position that they will not provide transformer nameplate impedances because the transformers could be changed out without customer notification. They have instead provided a range of impedances for a 300 kVA padmount of 2 to 6%.
I've done everything I can do to explain the need to their PE representative, but the engineer's response is that their legal department is making a final decision on the topic, but as it stands now they are denying our requests for dozens of facilities where we're doing arc flash analyses.

They will also only provide fault current contribution information at the medium voltage level (xfmr primary) along with a maximum fault current level at the secondary by using the 2% impedance level for the calculation.

The range of incident energy levels at the service-entrance gear for a 2-6% impedance variance is 2 to 26 calories, for which we will be forced to use the 26 calorie level as the worst-case calculation.

The engineer had just returned from a Utility Safety conference that emphasized the arc flash calculations are not exact and should not be used as such (her words), which is directly counter to 70E principles which are exact enough to permit reduction of Instantaneous levels for maintenance settings.

I'm not sure what to do at this point. The easy choice is to use the 6% impedance value and label the gear at 26 calories, but that's a disservice to our client. I've considered filing a complaint against the engineer with the VA PE board, because I see the behavior as irresponsible and uneducated.

Has anyone else seen a movement like this by Utilities? I think one could possibly make the case that perhaps the calculations are too precise since there are so many variables, like Utility strength at any given time for one. But my argument is that we're using the best process that's available and IEEE 1584 requires nameplate information, and as such the Utility is preventing the use of accurate information. This Utility initially advised that they would charge the client to collect the nameplate data, but have since rescinded that offer. And by the way, we have had success with two other Utilities in the area that are providing that information. This is the first Utility that has balked at this request and I sure hope it's not the start of a new trend.

Comments appreciated.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Tue Jan 02, 2018 1:00 pm 
Offline
Sparks Level

Joined: Fri Jul 08, 2016 10:01 am
Posts: 140
mayanees wrote:
There is an electrical Utility ...............of a new trend.

Comments appreciated.


I don't think transformers get changed out very often. At all. Unless of course there was a failure. If they were I think the customer would be very aware of that being done. Also, studies are supposed to be updated every 5 years so a change should be caught then if the customer didn't notice the several hour power outage and the heavy equipment outside changing their pad mount or pole mounts.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Tue Jan 02, 2018 1:07 pm 
Offline
Sparks Level

Joined: Fri Jul 08, 2016 10:01 am
Posts: 140
Also, their impedence range I think could be narrowed a bit from my experience. Pole mounts are often under 2% from what I've seen. I've not seen a standard oil filled pad mount that low that I can recall. More like a range of 3.5% to maybe 6% for those in the 300 KVA range.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Tue Jan 02, 2018 1:24 pm 
Offline
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 438
IEEE C57.12.34 shows a narrower range of 3.1 to 5.75% for a 300 kVA. The tolerance on the impedance is also defined by IEEE C57.12.00 as 7.5% in this case, putting your worst case at 6.18%.

I wonder if the same legal department will defend the PE before the board.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Tue Jan 02, 2018 1:54 pm 
Offline
Sparks Level

Joined: Fri Jul 08, 2016 10:01 am
Posts: 140
stevenal wrote:
IEEE C57.12.34 shows a narrower range of 3.1 to 5.75% for a 300 kVA. The tolerance on the impedance is also defined by IEEE C57.12.00 as 7.5% in this case, putting your worst case at 6.18%.

I wonder if the same legal department will defend the PE before the board.


That range aligns with what I've seen first hand. I have purchased a couple pad mounts with higher than "normal" impedance intentionally specified that way to reduce available fault current. I replaced a couple banks of 3 single phase cans wired for 3 phase with the higher impedance pad mounts. ABB had no issue with doing so. I usually buy ABB or Cooper pad mounts for the university at which I work.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Tue Jan 02, 2018 2:14 pm 
Offline

Joined: Tue Feb 17, 2009 8:38 am
Posts: 33
Location: Westminster, MD
I missed the previous post that referred to PUC cases - Public Utility Commissions. I just read though it and it refers to pretty much the same issue we're having with the availability of accurate electrical system information. So then I looked at the regulating authority for Virginia's Utilities and it's the State Corporation Commission, Division of Public Utility Regulation. I'll work with them to address the issue and will provide an update when I get one.

In response to an earlier post - to the Utility's PE who stated the transformer could be replaced at any time and that would change everything - I said just what you wrote: That's why there's a requirement to update the Study every five years.

Thanks for the comments and please keep them coming.

- John Mayan


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Tue Jan 02, 2018 3:40 pm 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1857
Location: North Carolina
To put it politely, the engineer at the Virginia utility you are dealing with is very uninformed. I've been working with at least a half dozen different utilities. None of them have acted that stupid. There are still a lot of questions and a learning curve...they are where general industry was at 10 years ago, but nothing like what you describe.

OSHA has taken a different stance in 30 CFR 1910.269. Utilities can and will address potential arcing hazards up to and including engineering calculations, period, regardless of how vague or questionable the results of the calculations. There is no longer an argument. It is required, period. May want to point this out and reiterate the request.

With respect to utilization systems (industrial plants) there is actually theoretically more wiggle room because it falls under the general duty clause. Industrial plants have to address it but specifically how that is done is left up to the end user unlike utilities where OSHA is specific and the limits are tighter than in general industrial cases.

Despite the fact that the calculations are basically untested, unproven, and currently not even public for anything over 15 kV, and the fact that there are really no good models for both outdoor overhead equipment and for vault-mounted equipment, OSHA did not make exceptions for questionable science or questionable calculations. The calculations, right or wrong, SHALL be used. That attitude might have applied in 2014 but since 2015, it is no longer acceptable by regulatory requirements.

There are significant differences though. The working distance is set to 15" rather than a variable 18-36" working distance. The "minimum" value is 2.0 cal/cm2 rather than 1.2 cal/cm2. The face requirement for PPE is somewhat relaxed. There is no "category zero". All qualified personnel will wear a minimum of arc rated PPE including long sleeve shirts and pants, almost without regard to the potential hazards, period. Risk assessments are required too and OSHA gives a table that is a lot better than the one in 70E-2015+. This is very different from how 70E and IEEE 1584 and ASTM 1959 treat arc flash.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Wed Jan 03, 2018 6:29 am 
Offline
Arc Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 697
Location: Rutland, VT
I think it should be noted that while OSHA has issued regulations for the utility industry regarding arc flash, OSHA uses the wording ..."the employer shall make a reasonable estimate of the incident energy to which the employee would be exposed."

I guess it would be possible for someone to construe that this means that the calculations are not exact which I don't think is the meaning here.

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 6:25 am 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1857
Location: North Carolina
The OSHA authored annex compares the Duke (Privette), Lee, 1584 (ignoring voltage limit), and Arcpro models. They basically cite Goldilocks...Lee and 1584 are too hit, Duke is too cold, and Arcpro is just right. There is also a several hundred page justification document, heavily footnoted, which provides the justification. It is clear that OSHA recognizes that particularly above 15 KV it's all guessing right now so they are clearly open to alternatives but what is also very clear is that SOME kind of estimating is required. They clearly left the door open for a supportable alternative.

EPRI is leading most of the research and so far their stance supported by IEEE (NESC) is that under utility conditions and with the extreme variability of results compared to calculations, an equipment type testing approach is the best option with calculations as a fall back. If you follow EPRIs work it makes the calculations look like a waste of time but the conditions EPRI is testing are mostly known outliers. The scariest one is meter sockets where IEEE 1584 falls short instead of overpredicting. Over in the basic research camp "arc absorbers" are proprietary but we'll known. As surface area increases or direct visibility of the arc is restricted in the equipment, the incident energy falls off dramatically, and the large box 1584 model is not very representative at all of common switchgear (overpredicts badly). Thus EPRI approach is much better when the equipment in question meets the criteria.

That is vastly different from the ostrich argument which is not supportable. Under the general duty clause certainly OSHA is clear that employers cannot be expected to protect employees against hazards where the science is lacking. That was certainly the case in say the 1990s and the reason enforcement actions did not occur until around 2006, and the reason enforcement actions on utilities was delayed for over a decade. But that horse has left the barn. There is clear room from OSHAs several hundred page "preamble" to the codified 1910.269 for legal action. But it would be difficult to mount a defense against enforcement actions without an active pending legal action taken to fight the regulation on the basis that the engineering is unsupportable. A claim of lack of knowledge about the change is theoretically possible but goes against basic legal assumptions that everyone knows and understands the law. I have never seen a case where that argument won and it would be a major precedent. I know there are some pending suits with regard to the 269 revisions though so you should be able to ask for a docket number. Even then as a matter of minimizing fines most employers would follow the regulation even with pending legal cases until such time as the legal case gets resolved as long as it is feasible to do so. In years past knowing under MSHA (The mining division of OSHA) there is approximately a 6.5 year legal backlog coal companies in the Appalachian region where mining operations often start, run, and end in 5 years would simply contest everything in court and force MSHA to drop the case when the mine closed. Now MSHA steps up to locking the gates and throwing people in jail if the fines don't work and there is nothing preventing OSHA from doing it too. Tyler Pipe in Texas came close. I've met DOJ people who were looking at my plant as a model for enforcement actions against McWane. That was an interesting discussion since I came from a Dupont-like background and the plant I was working at was a long ways from that level of safety but the DOJ folks said they wanted to look at a 'typical' plant, not a safety leader.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 8:35 am 
Offline
Arc Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 697
Location: Rutland, VT
mayanees - please keep the forum posted on your progress and final resolution.

I think my next utilities to tackle on not providing information are located in NJ and later this month I have a meeting with the client to determine how they want to proceed.

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 9:47 am 
Offline
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 438
mayanees wrote:
I missed the previous post that referred to PUC cases - Public Utility Commissions. I just read though it and it refers to pretty much the same issue we're having with the availability of accurate electrical system information. So then I looked at the regulating authority for Virginia's Utilities and it's the State Corporation Commission, Division of Public Utility Regulation. I'll work with them to address the issue and will provide an update when I get one.
- John Mayan


I suspect you will find the SCC does not regulate all the utilities, just those that are owned by investors. Cooperatives and municipals are generally regulated separately.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 11:10 am 
Offline

Joined: Tue Feb 17, 2009 8:38 am
Posts: 33
Location: Westminster, MD
stevenal wrote:
mayanees wrote:
I missed the previous post that referred to PUC cases - Public Utility Commissions. I just read though it and it refers to pretty much the same issue we're having with the availability of accurate electrical system information. So then I looked at the regulating authority for Virginia's Utilities and it's the State Corporation Commission, Division of Public Utility Regulation. I'll work with them to address the issue and will provide an update when I get one.
- John Mayan


I suspect you will find the SCC does not regulate all the utilities, just those that are owned by investors. Cooperatives and municipals are generally regulated separately.


I just found out that you are correct sir. The SCC does not have jurisdiction over government agencies, in this case the County.

The Utility is digging their heels in on this though.

For entertainment purposes to like-minded folks, here's the content of two recent emails:


from the Utility:
Hello again,
Let me address this one since I am an arc flash expert.
Transformers of this size (300kVA) do not come with test reports and it is not a simple process to retrieve nameplate data. The most conservative incident energy levels are achieved using impedance ranges. As you know, low fault current values could have a higher incident energy level than a high fault current because of the slower clearing times. Not only can the transformer be changed at any time, the source impedance changes often, and the protective device can change. I would be concerned about an Arc Flash calculation that uses precise values; however, since the PPE ranges are relatively wide, with only five categories between 0 to greater than 40 Cals/cm2, precision is not a requirement. If precision were necessary then changing out the transformer tomorrow could cause safety issues. With this said, if the PPE requirements appear unreasonable, then we should take a second look at the data and the calculations and I will be happy to assist you with this.

my reply:
And I consider myself an expert at arc flash concepts as well; and an expert in the application of NFPA 70E, which is the basis for the requirement for arc-flash labels, as I'm an NFPA-Certified Electrical Safety Compliance Professional.
My calculations show a range of IE levels for the impedances you provided from less than 2 calories for the low-impedance transformer to 25 calories for the high-impedance transformer.
If you don't supply the nameplate Z then they are inconvenienced with an unrealistically high incident energy posting as I will be forced use the worst-case scenario. And we all know you won't be buying a 6%Z 300 kVA transformer.
IEEE Standard 1584-2013 specifies the use of nameplate data so I adhere to that standard and advise accordingly. It is in the clients best interest to have an accurate representation of the hazard at their service-entrance switchboard. NFPA 70E requires that this information be verified every five years, so changes are caught.
I'm also not looking for test report data for a padmount transformer, although I know that information is available at the factory. The Army Corps of Engineers requires this for their Power Study submissions. The information I'm looking for is on the transformer nameplate: the impedance, %Z.
So will you provide the transformer nameplate information, or will our client's switchgear be labelled with a higher-than-likely incident energy level?

from the Utility:
My apologies if you felt insulted. I stated I am an expert because I am the appropriate person to answer the question.
The question here is, who would be liable if UTILITY NAME REMOVED provided (arc flash related) nameplate impedance on a transformer that could be changed out tomorrow, or the protection changed, or the source impedance changed? Providing nameplate impedance is risky for UTILITY NAME REMOVED and the customer, which is why we don’t (?sic) provide a range. We work with hundreds of companies and consultants and no one else is asking for nameplate impedance.
After recently attending an IEEE PES seminar on Arc Flash, I feel even stronger that the customer should be given conservation (conservative sic)PPE requirements. Customers do not understand the values consultants are providing to them, some consultants are not properly providing the variances / risk, and the customer is putting too much faith in these numbers. The drastic change in energy level quoted below is even more of a concern; if UTILITY NAME REMOVED changed out the transformer tomorrow and the value could easily shoot from 2 cals to 25 cals; this is extremely dangerous.

You couldn't even make this stuff up!

The State Corporation Commission responded and we talked. His suggestion was to pursue through OSHA. It's apparent to me that OSHA requires them to provide the info as evidenced by:
1910.269(a)(3)(i)(A) The characteristics of the host employer's installation that are related to the safety of the work to be performed and are listed in paragraphs (a)(4)(i) through (a)(4)(v) of this section;
Note to paragraph (a)(3)(i)(A): This paragraph requires the host employer to obtain information listed in paragraphs (a)(4)(i) through (a)(4)(v) of this section if it does not have this information in existing records.

The Utility's latest correspondence suggested that they would get the information but that we would be charged for that work. But the "Note to paragraph" as shown above clearly states they have to provide the info. If they stick to their statement that they'll get the info but will charge for it, then the County, as their customer will have to negotiate that.

I will keep you all posted.

Regards,

John Mayan


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 12:46 pm 
Offline
Sparks Level

Joined: Fri Jul 08, 2016 10:01 am
Posts: 140
I feel for you. Not to rub salt in the wound, well maybe a little. I feel fortunate. Here is an email from our utility when I asked for the same info as you on a facility that is not connect to our campus distribution system but is just a bit off campus that I modeled a couple years ago.

They've also sent me screen shots of their models including trip curves before without any resistance to the request at all. Of course, it may have something to do with the fact our peak demand each month is generally well over 20 megs and our bill is in the millions annually. We're a pretty large customer for them so they treat us pretty well.

Attachment:
Utility Example.JPG


You do not have the required permissions to view the files attached to this post.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 1:12 pm 
Offline

Joined: Tue Feb 17, 2009 8:38 am
Posts: 33
Location: Westminster, MD
bbaumer wrote:
I feel for you. Not to rub salt in the wound, well maybe a little. I feel fortunate. Here is an email from our utility when I asked for the same info as you on a facility that is not connect to our campus distribution system but is just a bit off campus that I modeled a couple years ago.

They've also sent me screen shots of their models including trip curves before without any resistance to the request at all. Of course, it may have something to do with the fact our peak demand each month is generally well over 20 megs and our bill is in the millions annually. We're a pretty large customer for them so they treat us pretty well.

Attachment:
Utility Example.JPG


... well thanks for that :)
I must clarify though that I've never had this level of ignorance from a Utility, and we've done hundreds of Studies over the past 5 years. The Utility in this case reiterated their position with the following:

Since our last correspondence, my management and other individuals involved had a meeting to address the issue of providing nameplate impedance to consultants for "Util name removed" customers. We came to the conclusion that we needed direction from our standards, safety, and legal departments before providing this information. We are concerned that using the nameplate impedance is not a safe practice for our customers. I personally believe this is an unsafe method of determining the worst case incident energy level over the four year period of review. As I noted before, a change in the distribution transformer can easily put the PPE requirements into a higher level of protection. Until we get direction from these groups, we won’t be providing nameplate data on distribution transformers.

So yes, I am in pain, but a little salt's good every now and then :lol:


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 2:03 pm 
Offline
Arc Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 697
Location: Rutland, VT
Quote:
it is not a simple process to retrieve nameplate data.


I find that statement hilarious. How hard is it to go to a padmount txf, unlock the padlock, use the pentagon wrench and open the low side door? And it is not PPE restrictive as NESC lists a 4 cal/cm2 incident energy for that task and I am sure their linemen or substation electricians open padmount doors frequently.

But seriously, I do understand/feel your pain! Keep plugging at them!

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Thu Jan 04, 2018 2:17 pm 
Offline
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 438
In my experience, 300 kVA padmounts do come with test reports. Testing is how they get the data to put on the nameplate. And if the data cannot be retrieved in digital or paper form, a qualified worker can always open the padmount door and look.

And yes, the IE calculated today may not be valid tomorrow as conditions change. I simply try to make this point when I provide data.

I'm not sure the utility can be considered a 1910.269 host employer here. They did not hire the consultant or the customer. Even if this applied, the standard requires sharing IE, not nameplate data. And speaking of 1910.269, it says nothing of the NFPA categories you contact speaks of.

Although I've never charged, I can see where a reasonable charge could be made.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Fri Jan 05, 2018 8:16 pm 
Offline
Plasma Level
User avatar

Joined: Tue Oct 26, 2010 9:08 am
Posts: 1857
Location: North Carolina
300 kVA transformers come with test reports IF you ask for it. Not all vendors provide automatically...it depends on the manufacturer. For example basic name plate data like date of construction is pretty much completely absent on Vantran transformers. They do the testing but unless you ask they keep it to themselves. And particularly when you get down to the small dry types, typically they do very little if any testing since often they simply average the results from several transformers, particularly if they are the mass produced types such as say GE or Square D ones. And some very local transformer manufacturers don't even really have the equipment since they are basically building them in a garage/home workshop. Plus if it's a local co-op/REA/EMC then chances are they are getting their transformers through the RUS program so they are buying based on a very generic specification and all the paperwork ends up in RUS, rarely making it through to the customer. This is the case with a lot of pole mounts and padmounts. So even though what you describe is very typical for Cooper, ABB, or Virginia, it does not apply to a lot of other manufacturers including Vantran, Howard, and others.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Sat Jan 06, 2018 6:55 am 
Offline
Arc Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 697
Location: Rutland, VT
My overall experience with the utilities I have dealt with is that they are very helpful with providing the information. Granted there are some that are not as I recently experienced (see my PUC post).

Utilities that have built robust models of their systems know what is on them including transformer impedances as that is used to determine the losses on their system. And utilities that I have dealt with that are unsure of the validity of the data in their system model, will send a crew out to get the nameplate impedance, fuse size, riser cable for padmounts, etc.

So far, I have not run into a utility that charges for this information.

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Mon Jan 08, 2018 9:00 am 
Offline
Arc Level

Joined: Thu Jan 10, 2008 8:49 pm
Posts: 483
Location: New England
Run the calcs at the 3% and the 6% (or whatever they tell you is the min or max impedance). Use the value that produces the highest IE values.

This is NOT an exercise in mathematics, its about safety. The numbers are ok to be wrong, as long as they err on the conservative side. Overall, this probably won't change downstream all that much after the main breaker anyways.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Utility refusal to provide service transformer impedance
PostPosted: Mon Jan 08, 2018 9:39 am 
Offline
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 438
Another thought: If the utility in question is a government agency such as a municipal or PUD, you may be able to do a "public records request." Government records are generally considered public unless they meet specific conditions. Such a request might reach different decision makers at least.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 20 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 1 guest


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
© 2017 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883