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 Post subject: Multiple sites with low load ratings
PostPosted: Thu Jun 10, 2021 3:04 pm 

Joined: Mon Sep 02, 2019 12:44 pm
Posts: 2
I am responsible for amongst a number of other things -175 aging Concrete batching plants around Australia - all are supplied from a pole mounted transformer via fuses at 400V.
The sites range in size according to Load ratings from 150A to 700A at approximately 50 A increments with the majority of the sites being rated at 250A.
All sites are basically of the same configuration; and typically consist of a main Switch feeding an MCC which feeds 2 conveyors (11kW ea) a mixer (45kW), Compressor(37kW), 3 Silos, Plant lighting and an admin office and a batching control room.
We just cannot afford the $4000 per site for an Arc Flash Study!
I was hoping to use the IEEE 1584 spreadsheet in order to perform generic AF calculations on typical sites ranging from 150A;200;250;300; ...700A) to determine the worst case scenario per rating and whether I could apply these results to all plants of the same load?

Any advice would be most welcome.


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 Post subject: Re: Multiple sites with low load ratings
PostPosted: Fri Jun 11, 2021 11:59 am 

Joined: Thu Apr 18, 2019 11:42 am
Posts: 49
Perform generic studies at your own risk. Differing transformer impedances, available fault currents from the utility, etc. My opinion, but I don't think that is a good idea.

Mike


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 Post subject: Re: Multiple sites with low load ratings
PostPosted: Sat Jun 12, 2021 1:51 am 
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Joined: Tue Apr 17, 2012 8:19 am
Posts: 244
Location: Charlotte, NC
mpparent wrote:
Perform generic studies at your own risk. Differing transformer impedances, available fault currents from the utility, etc. My opinion, but I don't think that is a good idea.

Mike


Agreed. If you don't want to pay for a professional to do the study, you will need to do the study yourself (hopefully by someone who knows how to do it). There is software available - likely at a lower overall cost than paying for each individual site. There are too many possible variables to generalize given a plant's amp load or kilowatt rating.


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 Post subject: Re: Multiple sites with low load ratings
PostPosted: Sun Jun 13, 2021 3:54 pm 

Joined: Mon Sep 02, 2019 12:44 pm
Posts: 2
Thanks very much for taking the time to respond I was hoping for someone who had been faced with the same dilemna - I will gather as much detailed info as possible and do the spreadsheet calcs, ask for a professional opinion on the results and then take action.
Hard to motivate and justify a spend of over $700k when there have been no incidents on 175 sites spread around the country in over 30 years..


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