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Showing posts with label shocks/burns. Show all posts
Showing posts with label shocks/burns. Show all posts

Thursday, February 24, 2011

Electric Shock and Electrical Burns

The 12.5% of the test on Codes and Standards includes the NEC, National Electrical Safety Code (NESC) and Electric shocks and burns. I already went over the NEC so today it was on to shocks and burns.


Electrical shocks and burns is really the domain of NFPA 70e: Standard for Electrical Safety in the Workplace, and if you want to learn how to do Incident Energy and Flash Protection Boundary Calculations, Annex D of NFPA70E is a good resource, but if you don't feel like reading through all that and just want to familiarize yourself with the subject, Mike Holt has a short article on Electric Shock and a longer one on Electrical Burns.

I'm not really sure what kind of questions the NCEES will ask on Electric shock and burns. I could envision a question on calculating arc flash protection boundary distance question or a maximum safe shock duration.
  • Calculating Arc Flash Protection boundary distances is straight out of Annex D of NFPA 70e
  • To determine the maximum safe shock duration according to IEEE Std. 80, you can use the formula, T=0.116÷(E÷R), where T is duration in seconds, E is the electromotive force in volts, and R is resistance of the person, which is a constant 1,000 ohms.
Ugly's has a handbook for Electrical Safety and NFPA 70e which has some calculations in it that mirror Annex D. Google books has a preview of it which gives you a free 20 or so pages.

NEC digest also has a good article on PPE person protective equipment and burns