It is currently Fri Aug 14, 2020 4:04 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Xcel Energy
PostPosted: Tue Oct 29, 2019 4:39 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
Has anyone had to deal with Xcel Energy to obtain system data to perform an arc flash study? For a client in Xcel's MN territory, all that Xcel will provide is the transformer kVA, Primary & Secondary Voltage and configuration. They refer one to their installation and use manual which just gives infinite bus fault current. Xcel also stated that the PUC approves this.

The last time I ran up against a utility that would not provide available fault current, I went to the PUC in that state and after much educating the PUC, the PUC directed that utility to provide the information. I am hoping not to have to go that route this time.

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Wed Oct 30, 2019 8:50 am 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
For secondary voltage customers, I have never gotten anything from Xcel except the values from their manual.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Wed Oct 30, 2019 10:15 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
JBD wrote:
For secondary voltage customers, I have never gotten anything from Xcel except the values from their manual.


So how are people meeting the NEC 70 Art 110.16 requirement for labeling service equipment over 1200A with the available short circuit current? MN is a state that has adopted the NEC 70 2020 edition that contains that requirement.

Also, how are you doing valid studies with only infinite bus fault current?

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Thu Oct 31, 2019 7:28 am 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
wbd wrote:
JBD wrote:
For secondary voltage customers, I have never gotten anything from Xcel except the values from their manual.


So how are people meeting the NEC 70 Art 110.16 requirement for labeling service equipment over 1200A with the available short circuit current? MN is a state that has adopted the NEC 70 2020 edition that contains that requirement.

Also, how are you doing valid studies with only infinite bus fault current?


The NEC 110 requirement is for a value of fault current sufficient to select the correct equipment. The utility supplies a 'not to exceed' number so this requirement is met.

For arc flash you need to apply engineering judgement rather than simply using infinite bus values.

Maybe your company has a data base of thousands of studies to draw from so you can determine somewhat realistic min, max, and average fault levels, which would allow you to create 4 different scenarios to use in your analysis.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Fri Nov 01, 2019 1:40 pm 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
JBD wrote:

The NEC 110 requirement is for a value of fault current sufficient to select the correct equipment. The utility supplies a 'not to exceed' number so this requirement is met.



I would respectfully disagree with that. The language in NEC 70 Art 110.16 specifically states "available fault current at the service overcurrent protective devices" and requires the "the clearing time of service overcurrent protective devices based on the available fault current at the service equipment"

The NEC 70 Definitions section defines Fault Current, Available (Available Fault Current) as The largest amount of current capable of being delivered at a point on the system during a short circuit condition.

It is very clear that the NEC is requiring available fault current not bolted fault current based on an infinite bus.

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Mon Nov 04, 2019 6:04 am 

Joined: Mon Mar 13, 2017 8:43 am
Posts: 1
This post is quite timely...I have come across the exact same initial response from Xcel Energy in MN no more than a week ago. They actually stated that "rules have changed" (I presume they were referring to Xcel internal rules) and that they could only provide the basic kVA, Pri, Sec Voltage and the infinite bus tabulated values.

I managed to get on the phone with the engineer that had provided this initial response and after a brief discussion about the impractical use of infinite bus info for an arc flash study, he decided to go ahead and provide me actual 3-phase and 1-phase fault kVA as well as positive and zero seq X/R.


Top
 Profile  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Wed Nov 06, 2019 11:43 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
Gianni - I sent you a PM

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Mon Nov 25, 2019 10:20 am 
Sparks Level

Joined: Sat Apr 04, 2009 9:50 pm
Posts: 105
Location: San Antonio, TX
If the utility only provides the infinite value for ASSC, here is what you can do.

1. If you want to satisfy NEC 70 to report the ASCC at the service equipment, you can calculate it based on the infinite value of contribution from the utility. This will give you the WORST case value of ASCC in the service equipment, satisfying NEC 70.

2. If you also need to calculate the AFIE at the service and through the rest of the system, refer to the IEEE paper named: IMPACT OF AVAILABLE FAULT CURRENT VARIATIONS ON ARC-FLASH CALCULATIONS. With this method, you will have a high probability of finding the worst-case AFIE on the system when the exact value of the contribution is not known.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Tue Nov 26, 2019 5:43 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
RECS - the issue with your response 1 is that it is not the available short circuit current. That is for an infinite bus which is wrong based on the definition of available short circuit current and would not comply with the NEC requirement of posting the available short circuit current.

I do have that IEEE paper but that does not help with the transformer impedance, riser fuse, riser cable.

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Tue Nov 26, 2019 9:01 am 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
WBD,

How much room is on that label? Are you collecting information on the service transformer as well as the full range of possible replacements, as well as all the alternate feeds and every possible permutation? Don't forget the NEC is not a maintenance code, so the label will likely remain static as source impedance changes over time. You may be correct regarding the (poor) code wording, but common sense tells us a not to exceed value will satisfy the intent. Have you had an inspector flag this as an issue?


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Wed Nov 27, 2019 7:29 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
Stevenal -

I am working on an electrical systems study which will include incident energy values for all the equipment included in the study. In my modeling, I will model the electrical system starting with the riser pole in. As such, I usually obtain and have no issues obtaining, the following info:
3 ph available fault current and X/R
SLG available fault current and X/R
Transformer - prim volt, connection, kVA, impedance
Riser fuse data
Riser cable data

This provides the most accurate results especially at the service entrance cable.

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Wed Nov 27, 2019 1:15 pm 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
stevenal wrote:
How much room is on that label?


The 2017 NEC requires the service equipment to have a label showing the available fault current as well as the fuse opening time.
There are several POCOs in this area that will provide only a 'design' level fault current and no fuse information at all.

There are things we can do to arrive a reasonable arc flash study, however I don't know how contractors are meeting the NEC.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Wed Nov 27, 2019 4:38 pm 
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
I messed up and failed to read the section in question. Instead I followed JBD's lead and assumed it was for equipment sizing. I see now it is for arc-flash. But the labeling required misses 70E information like IE and PPE category, and includes stuff not required by a 70E label. I think I would take the exception and provide a 70E style label. While utility data would still be preferable, you'd be able to use the IEEE method RECS mentioned to get a reasonably conservative IE.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Mon Jan 06, 2020 9:03 am 

Joined: Thu Apr 18, 2019 11:42 am
Posts: 18
I have had interaction w/ Xcel for a number of years...no issues getting available fault current, etc. in Colorado.

Mike


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Tue Jan 07, 2020 6:06 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
Thanks Mike. I sent you a PM

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Tue Jan 07, 2020 12:37 pm 

Joined: Thu Apr 18, 2019 11:42 am
Posts: 18
wbd,

I saw the PM you sent. I'm not sure how to reply though...a message pops up and says I don't have sufficient privileges? I would rather respond in private.

Mike


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Tue Jan 14, 2020 5:50 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
I have received a response from the MN PUC from Xcel regarding my complaint on not providing the available short circuit current. Here it is for those interested. I will respond to them in the near future with an argument on why the information is needed.

We have received the CAO complaint filed by Barry Donovan, P.E. Vice President of Workplace Safety Solutions, Inc. on behalf of his un-named client. He has requested that Xcel Energy provide system fault current data in his client’s facility so that the client may perform an Arc Flash Study.
The type of information that is required to prepare a special study would necessitate additional work by Xcel Energy in the form of a special study. To our knowledge, there is no requirement stating we must perform special studies respond to this type of request. Further, even if we were to do a special study, the results would be applicable for a specific point in time. Our system is constantly changing via switching and circuit reconfiguration. The information that we are being asked to provide under such a study would not be representative of the range of possible system configurations in the future. We believe use of this static current information could lead to incorrect values of arc flash energy to determine what type of personal protective equipment (PPE) should be used on a prospective basis given that this information does not reflect the possible range of future system conditions.
In our experience, most engineering firms use software to solve for the energy available in considering an Arc Flash Study. Once Xcel Energy provides the maximum fault current available assuming an infinite bus and the protective device rating, engineering firms are able to run the software and conduct their study. We receive over a thousand similar requests each year and successfully respond to these requests in a similar manner.
If we were to be required to provide this type of information as requested by Mr. Donovan, it would be a fundamental shift in policy. Further, before doing so, we would need Workplace Safety Solutions, Inc. and their client to sign a release and indemnity agreement so as to protect Xcel Energy from exposure to liability and financial damages in the event that property is damaged or if someone is injured due to improper application of current Xcel Energy system data as a proxy for the continuously changing Xcel Energy System. The process to obtain such a release and indemnity agreement is not clear as currently we do not have a tariffed form for this.”

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Wed Feb 12, 2020 6:11 am 

Joined: Fri Sep 28, 2018 7:32 am
Posts: 11
Location: Evansville, IN
wbd wrote:
Has anyone had to deal with Xcel Energy to obtain system data to perform an arc flash study? For a client in Xcel's MN territory, all that Xcel will provide is the transformer kVA, Primary & Secondary Voltage and configuration. They refer one to their installation and use manual which just gives infinite bus fault current. Xcel also stated that the PUC approves this.

The last time I ran up against a utility that would not provide available fault current, I went to the PUC in that state and after much educating the PUC, the PUC directed that utility to provide the information. I am hoping not to have to go that route this time.


I initially was given their standard for electric installation and use manual. After prying a little bit I received an "Arc Flash Data Request" form for a property they serve in Englewood, CO. It identifies the maximum fault currents and X/R values. Additionally, they identified the upstream fuse protecting their step-down transformer.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Fri Feb 14, 2020 1:54 pm 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 823
Location: Rutland, VT
Attached is what I received from Xcel initially. It does give much and the manual referred to provides infinite bus fault current on secondary. I have not yet responded to Xcel reply to the PUC due to work load but will do in the near future.


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

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Tue Feb 18, 2020 8:17 am 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
wbd wrote:
I have not yet responded to Xcel reply to the PUC due to work load but will do in the near future.


Yet Xcel has no problem providing the requested information for customers that purchase power at MV levels. Is their LV distribution system really that much different than their MV one?

I wish you good luck. We gave up the fight years ago and developed some methodologies that we feel provide a reasonable estimate of worst case AF results (we have been known to run 20 scenarios).


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


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