Personal Arc Protection Calculation 4

[tmaly1]

folks,

does any of you know the basic empirical equations used to calculate arc-flash energy produced by fault currents on 13.8 kV system. I've calculated the SC current on our system but I don't know how to convert the results into arc energy required to specify protection cloth/tools.

I appreciate your help and feedback.

Thanks in advance

 

[cuky2000]

See the enclose sample calculation from SKM

http://www.skm.com/support/kb/120004.doc

 

[cuky2000]

The standard, IEEE 1584, "Guide for Performing Arc Flash Hazard Calculations," could be a good guide to start.

Enclose please find a simple version in Excel based in IEEE Std 1584.

http://grouper.ieee.org/groups/1584/simple.xls

 

[alehman]

Try NFPA 70E "Standard for Electrical Safety in the Workplace". It defines requirements for personal protective equipment based on available energy. It also includes generic tables for a variety of conditions and types of equipment for use when calculations are not available.

 

[RonShap]

alehman,
The generic table in 70E for when calcs are not available, require calcs to use it. You have to determine the bolted fault current and clearing times of the OCPD (which requires calculation of the arc flash fault current).

 

[alehman]

RonShap: Thank you for the correction. The tables in 70E do require classification of available fault current and clearing time for low votlage equipment into one of 5 categories. Also, there are revisions now being proposed for the categories.

The tables are provided 'in lieu of the detailed flash hazard analysis approach', which involve the incident energy calculations mentioned by tmaly.

 

[mgs1209]

tmaly1: Download this ELECTRIC ARC HEAT FLUX calculator and input your appropriate variables. This should give you some sort of idea as to what type of arc energy/heat will be delivered at a pre-determined distance so that you can apply the appropriate CAL/CM clothing/tooling to be used for proper protection. Do read the help file, it is VERy informative.

http://www.saftgard.com/heatflux.htm

 

[dpc]

If you're looking for the equations, IEEE-1584 is the repository of the empirical equations that were developed based on various tests done up to 15 kV. NFPA-70E-2004 has a different set of equations, more theoretically based, in the Annex in the back. The basis for the NFPA-70E equations goes back to the original paper by Ralph Lee, and are often referred to as the "Lee Equations".

If you are trying to develop an electrical safety program to comply with NFPA-70E requirements on arc-flash protection, you should probably buy NFPA-70E and also IEEE-1584, although there is no inexpensive way to purchase the IEEE standard.

 

[tmaly1]

Dear folks,

I was overwhelmed by the responses and help I got from all of you. I'm really grateful to be part of this great community. I appreciate you sharing your knowledge and experience with me. May God bless you all

millions thanks

 

[CJFlatters]

Hi

The Bussmann website has some very useful data on Arcflash - suggest you take a ganders at their website

Using IEC269 / BS88 Fuses is a good way to reduce the I2t and therefore reduce Arcflash

http://www.bussmann.com/apen/pubs/spd/

_______________________________________
Regards -

Colin J Flatters
Consulting Engineer & Project Manager