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 Post subject: Arc Flash Detection Relays accounted for in Study?
PostPosted: Wed Jul 31, 2013 10:37 am 

Joined: Mon Oct 19, 2009 7:42 am
Posts: 30
Curious if anyone is using arc flash detection relays in their equipment? If so, are you accounting for its use in your incident energy calculations? Do any of the standard arc flash analysis softwares (SKM, ETAP, Easy Power, etc) model arc flash detection relays or provide a way for their consideration in the calculations to determine incident energy?


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PostPosted: Wed Jul 31, 2013 4:50 pm 
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Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
In SKM version 7, you can basically tell it to assume a trip time of I think 1 cycle. Unless the currents are just off the chart ridiculous, it usually reduces the incident energy to <1.2 cal/cm^2. You just select it as a toggle since there are a huge variety of devices that can give the fast tripping function including more traditional ones such as differential relaying. I'm not sure how it would handle zone protective relaying since this results in a slower instantaneous trip function but lets you effectively use instantaneous or otherwise do things that would otherwise be considered miscoordination on a time-current curve.


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PostPosted: Mon Aug 05, 2013 3:55 pm 

Joined: Sun Jul 22, 2007 5:00 pm
Posts: 31
Location: Stratham, SW Australia
SKM/PTW Arc Flash program enables users to select fault clearing times on individual user selected buses.
The default clearing time setting ( Global maximum arcing time ) for all buses is 2 sec, if the timed phased overcurrent protection time plus CB clearing time is less than 2 sec, the protection operate plus CB clearing time is used to calculate the arc flash hazard.
A typical setting for zone protection or arc detection relay would be 0.1 sec. If a bus is individually selected for a 'maximum arcing time' of 0.1 sec then this time will be used to calculate the arc flash hazard.


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PostPosted: Thu Aug 22, 2013 7:11 am 
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Location: Rutland, VT
EasyPower allows user defined trip times to be inputted per bus. This way one can add up the relay actuation time, clearing device time, signal propagation, interposing relays, etc. and use that time as the device clearing time.

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PostPosted: Fri Sep 06, 2013 5:48 pm 
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Joined: Sat Feb 27, 2010 5:59 pm
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Location: Cincinnati, OH
mnewman wrote:
...If a bus is individually selected for a 'maximum arcing time' of 0.1 sec then this time will be used to calculate the arc flash hazard.


This would not be a preferred method for manually entering a clearing time for high speed protection - at some point in the future other individuals may need to use the model you create when you are unavailable and they would probably not expect a manually calculated clearing time to be entered in this way. The maximum arcing time field in all of the major software packages would typically be set to a global default of 2 seconds and individual buses could be set to longer values if there is limited egress from that equipment (e.g. access via an overhead lift) or even for a specific task (e.g. phasing in Magneblast switchgear).

The preferred method for entering manually calculated clearing times is to add the desired clearing time in the bus properties. Some software packages allow us to enter a function ID name along with the clearing time, then the function ID (87B, ZSI, optical arc flash relay, etc.) is listed in the arc flash report along with the corresponding clearing time, incident energy, etc.


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