When talking about the hazard of a 480v load center, ours range from a low of 16.1cal/cm2 to a high of 25.1 cal/cm2. So using 4 cal/cm2 as a base for your hazards would be a bad assumption. For 480v MCC busses we have a low of 10.6 cal/cm2 and a high of 38.1 cal/cm2. Your calculations need to...
I agree with much of what you have said, my only issue is when you place the onus of securing ones own safety on the worker. That worker is not necessarily up to speed on the recent information we now have available with the new calcs. I know that I could not have performed the new calcs...
NFPA 70E's Arc Flash calcs were shown to be faulty 2-3 years ago by IEEE. Since they left out the times associcated with fault detection relays, trip relays and any other vital equipment required to clear a fault. Now that we know we have much higher arc flash energy than the original calcs...
I agree that 480v MCC's do not need flagged off nor do we need PPE to be in the area. We roped off our 13.8kv switchgear rated at 76.5 cal/cm2. We have considered roping off the 4.16kv switchgear as well since they are all in the mid 30's of cal/cm2. The need for anyone to casually walk in...
That is why when we learned of the blast effects and determined our cal/cm2 energy levels, we installed remote breaker racking. We looked into everything on the market and found that most of the systems were simply remote switches that had slight differences in how they did the job. We...
I would like to comment on the question about probability and risk. One of the things we have to remember is that there are 5-10 arc flash incidents in the US each day. We also have to remember that even the newest and best components can fail. We were just months away from our plant start up...
http://www.powermag.com/ExportedSite/Archives/Archives.htm
They did an accompanying article on our project that is linked in the first paragraph or so under (see box).
We recently performed new calcs that include each component in the system using the exact equipment we have in our system. Our calcs show that even our 489v load centers are in the 20cal/cm squared levels. The NFPA 70E and other arc flash software are not using real values for specific...
The comments about passing by the bus with no interaction seems to make sense until you have a fault on a 13.8kv bus that blows the 170lb door off of the hinges, breaks the latches and the door stop and throws the door 25 feet into another bus. We had that happen 23 years ago and now we...
I am the project manager for our plants remote breaker racking project. We are installing Safe-T-Rack systems in all 90 of our plants 13.8kv & 4.16kv breakers. We completed phase one with 34 breakers last fall and are very happy with the system, the ease of installation and the performance of...
