It is currently Thu Feb 22, 2018 3:46 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Arc Gap for Transmission Stations
PostPosted: Mon Jun 30, 2014 6:21 am 
Offline

Joined: Mon Jun 30, 2014 5:29 am
Posts: 3
OHSA’s new requirements indicate an evaluation of both single phase to ground faults and three phase faults should be performed above 15kV. For transmission stations (115kV and above), what criteria are you using to select the arc gap for three phase faults.
I initially was going to employee the spacing between the phase bushings (transformer, breaker,…), although the phase spacing between the bus conductors (or bus bar) would be the largest phase to phase spacing. What are everyone’s thoughts on this topic?
Thanks
Dan


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Arc Gap for Transmission Stations
PostPosted: Mon Jun 30, 2014 8:55 am 
Offline
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 711
Location: Rutland, VT
If you are using ArcPro to do the analysis, then you don't need the gap spacing for three phase. In ArcPro, 3 phase open air arcs are derived by using a multiplier on the single phase result. This is acceptable to OSHA (see footnote 4 to Table 3 in Appendix E 1910.269)

The question really becomes what do you use for an arc gap for single phase? I have seen the insulator on a gang operated switch used as the gap and I have also seen the insulator height plus 15% used.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Arc Gap for Transmission Stations
PostPosted: Mon Jun 30, 2014 10:10 am 
Offline

Joined: Mon Jun 30, 2014 5:29 am
Posts: 3
Thank you for the reply. I planned on calling Kinectrics to discuss the application of the multipliers. When reading through the work EPRI did, I interpreted the multiplier as an adjustment to account for the fact that there is more than one arc but I could be completely off.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Arc Gap for Transmission Stations
PostPosted: Tue Jul 01, 2014 3:47 am 
Offline
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 711
Location: Rutland, VT
The Help Section has the multipliers in it, Section 9.0 of ArcPro manual states about the multiplier. Please report back on your discussion with ArcPro. I have had some difficulties with emailing questions and getting timely responses.

Also what are you using for your Arc Gap distance?


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Arc Gap for Transmission Stations
PostPosted: Tue Jul 01, 2014 8:19 am 
Offline

Joined: Mon Jun 30, 2014 5:29 am
Posts: 3
I discussed the multipliers for a three phase fault with Kinectrics. When evaluating a three phase fault the three phase arcing current, arc duration associated with that arcing current, and the arc gap associated with that arcing current should be entered into Arcpro then the multiplier should be applied. He mentioned it is important to note that updated multipliers are included in the latest version of Arcpro.

At this point I think for single phase to ground faults we will continue to utilize the arc gaps provided by NESC and OSHA, although this is still under discussion.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Arc Gap for Transmission Stations
PostPosted: Tue Jul 01, 2014 2:01 pm 
Offline
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 711
Location: Rutland, VT
So just to clarify:
Kinectrics said to use the 3 phase values and then the multiplier???

This goes counter to their published information with the latest version of ArcPro. In the manual it specifically states that the single phase incident arc energies are multiplied by a factor. Also the Help section of the software states that the single phase arc energy may be adjusted by the following factors with the multipliers listed.

The below statement is from Stephen Cress, one of the developers of ArcPro, in a email to me dated 4/17/14, which seems to still indicate that the single phase value is what is multiplied.

Quote:
The basis for the factors is an engineering analysis of all published test data both from Kinectrics and IEEE and a comparison of this with Arcpro outputs. Arcpro models single arcs, either phase to phase or phase to ground, so without the factors it produces results applicable to single arc situations. Note that IEEE1584 models only 3-phase situations. Essentially the factors adjust the output of Arcpro to yield the best match to the 3-phase and in-box test data that exists. Feel free to call if you wish more detail.


I would be interested to see from Kinectrics the statement about using the 3 phase values as inputs and then apply the multiplier.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Arc Gap for Transmission Stations
PostPosted: Wed Jul 02, 2014 9:29 am 
Offline
Arc Level

Joined: Tue Jan 13, 2009 5:00 pm
Posts: 442
markisd wrote:
OHSA’s new requirements indicate an evaluation of both single phase to ground faults and three phase faults should be performed above 15kV.


Where exactly is this indicated?

markisd wrote:
He mentioned it is important to note that updated multipliers are included in the latest version of Arcpro.


Which version is latest? I'm still hoping for a version that will run on a 64 bit machine, but Kinectrics has ignored my emails.


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Arc Gap for Transmission Stations
PostPosted: Wed Jul 02, 2014 11:45 am 
Offline
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 711
Location: Rutland, VT
stevenal wrote:
markisd wrote:
OHSA’s new requirements indicate an evaluation of both single phase to ground faults and three phase faults should be performed above 15kV.


Where exactly is this indicated?


OSHA requires the employer to make a reasonable estimate of the incident energy to which an employee would be exposed. There is no limit on the voltage level. There is a table in Appendix E which lists what methods OSHA would consider reasonable and the table headings are 600V and less, 601 V to 15kV and More than 15kV. One has to decide about SLG or 3 phase exposures.

wbd wrote:
markisd wrote:
He mentioned it is important to note that updated multipliers are included in the latest version of Arcpro.


Which version is latest? I'm still hoping for a version that will run on a 64 bit machine, but Kinectrics has ignored my emails.


I see you have the same issue I have with Kinectrics on their responses to emails. I have put tracers on the emails and know they are received, read but rarely replied to. Customer Service and after purchase support is not the best, IMHO. One would think with OSHA prominently mentioning ArcPro they would have a new version to run on a 64bit machine. Running XP Virtual is clunky!!


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


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