It is currently Sat Aug 08, 2020 1:28 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Xcel Energy
PostPosted: Thu Jun 04, 2015 10:47 am 

Joined: Fri Feb 13, 2015 9:27 am
Posts: 8
Location: Hendersonville, TN
Has anyone else had trouble getting fault current values from Xcel Energy? We were told all that would be provided on secondary metered services would be infinite bus calculations. I am not a big fan of doing calculations for arc flash based off infinite bus numbers.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Thu Jun 04, 2015 11:18 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 822
Location: Rutland, VT
I have not had to deal with Xcel Energy but a long time ago I did have an issue with a utility as all they would give were infinite bus. I solved the issue by:
1. Pointing out that IEEE 1584-2002 states to obtain utility max and min available fault current
2. Explained that infinite bus could lead to employees having inadequate PPE since an infinite bus in not necessarily conservative for arc flash analysis.
3. After 6 months of going back and forth with utility, I explained that I was at the point where I needed to file a complaint with the regulators (Public Utility Commission)

Shortly after I stated my only option left to protect employees was Item 3, I received the necessary information.

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


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Thu Jun 04, 2015 11:34 am 

Joined: Fri Feb 13, 2015 9:27 am
Posts: 8
Location: Hendersonville, TN
Thanks for the reply Barry. Its sad that you have to threaten to get information that you know more than likely they have in a model and they just flat out wont give it to you. We have been dealing with them for a while on these two locations and were pretty much told today that it was the company policy not to give the data out on secondary metered services.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Fri Jun 05, 2015 5:10 am 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 523
Location: Wisconsin
According to Xcel Energy's 'Standard for Electrical Installations and Use' handbook:
Quote:
It is the intent of the Company to address a customer’s need for information concerning arc flash data requires as follows.
For Secondary Voltage Services the Company will provide, upon request from the customer:
1. Transformer size, primary voltage, secondary voltage, and typical percent impedance
2. Transformer primary fuse information size and type.
3. Maximum available secondary symmetrical three-phase fault current, from Tables 1A through V in this Section.

Tables 1A through V in this Section are only intended to provide the basic information necessary for secondary service customers to make their own
internal system fault current and arc flash calculations.
Primary service customers will still need to consult with a Company Area Engineer, to obtain fault current and protective device information for their service locations.



I would bet that 90% of utilities actually do what Xcel does, they just don't publish the information.
Our firm's policy is to run several scenarios using different fault current values in an effort to create a 'worst case' value.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Mon Jun 08, 2015 7:11 am 
Sparks Level

Joined: Fri Apr 15, 2011 7:43 am
Posts: 177
Location: Colorado
I am in XCEL territory and they have a policy to only provide fault currents that they have published. You can find this directly from them if you know the size of the transformer. If you do not know anything on the power system the account holder must find this out (and engineering firm or other must have a letter giving permission to get that info)

here is where you can get the info http://www.xcelenergy.com/Start,_Stop,_ ... r_Builders


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Tue Jun 09, 2015 7:53 am 
Sparks Level

Joined: Fri Apr 15, 2011 7:43 am
Posts: 177
Location: Colorado
Here is an update to get the XFMR data:
https://www.xcelenergy.com/staticfiles/ ... /Corporate PDFs/XcelEnergy_Standard_For_Electric_Installation_and_Use2014.pdf


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Mon Jun 15, 2015 7:43 am 
Sparks Level
User avatar

Joined: Sun Jan 04, 2009 5:00 pm
Posts: 285
Location: Louisville, KY
We have frequently received the same reply from utilities. We typically will travel the nearby substation and look at the transformer types to estimate. Infinite bus is really a liability to the utility. They are saying they "guarantee" infinite bus? So their breakers will trip really fast and protect you and the fault current is really high so your devices will trip fast? That is unlikely. When you explain that to the utility engineer they will typically come back with a min/max level. They have this information in every case we've been able to dig into so it is just a matter of getting min/max. Never depend on them clearing as the upstream breaker since most utilities don't do regular breaker exercising or maintenance except in the power plants and crucial operations which have negotiated low down time.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Xcel Energy
PostPosted: Thu Jun 18, 2015 7:25 am 
Plasma Level
User avatar

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1499
Location: Scottsdale, Arizona
Having headed up the short circuit studies group for a very large public utility in a past life, it really depends on the utility's staff, capabilities (and the lawyers) We would provide pretty detailed information and also provide line out contingency conditions as well as attempt to project for the future based on the company's future plans. We also then surrounded this information with legal disclaimers about how the data is based on normal conditions, the system can change, etc. etc.

The infinite bus case "might" be the worst case for the arc flash assuming the minimum case doesn't cause devices to time delay but there is no way to know for sure without the data. A few weeks ago I did a webinar about utility data and one of the areas I touched on was how to deal with a lack of utility data.

WEBINAR - Utility Short Circuit Data

The short summary is you begin with an infinite primary source (assumes 0 source impedance) and run the study using the transformer secondary short circuit results. As an example, a 1500 kVA transformer with a 480 volt secondary and 5.75 percent impedance has a secondary short circuit current of 31,374 Amps (excluding motor contribution).

Run the study with this value an see if the arc rating of the PPE is sufficient. Then reduce the current in 5 or 10 percent increments and continue to rerun the study and verify the arc rating is still sufficient. At some point, the SC current will become too low and you will see incident energy values increase dramatically.

At this point you have found the minimum fault current where the PPE results are valid. This isn't a perfect answer but it gives you a range of currents where the calculations indicate the PPE arc rating is sufficient.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 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