Past – Present – Future
By Jim Phillips, P.E.
Blog #3: Evolution in Forensic Electrical Engineering
There has been much advancement in the field of forensic electrical engineering since the days of Morse, Latimer, Edison and others. A few of the more significant advancements include:
- Better Understanding of Electric Shock and Arc Flash Hazards
- Codes and Standards
- Computer Simulations
Personal injury that is a result of contact or exposure to energized electrical conductors is usually due to electric shock/electrocution and/or burn injury from an arc flash. In the early years of electrical power systems little was known about these hazards other than they can occur. Today, research, testing and new and improved electrical standards have greatly expanded the knowledge of these hazards. Continue reading
I was asked to evaluate some “newer” bus duct technology that are finger safe, use a turn and lock connection or similar methods without turning off the power. It seems to do a great job at significantly reducing if not outright eliminating the shock hazard. It also looks like the risk of causing a fault when installing or removing a module is reduced (eliminated?) as it seems it would be very difficult to short line to line or line to ground. Therefore the arc flash risk greatly reduced (eliminated?). Assuming there is > 1.2 cal/cm2 energy available, is there still a arc flash hazard here? Comments on Labeling? PPE?
For example only as there are other manufactures with similar technology. https://www.youtube.com/watch?v=B03Bnhh6w8E
The surface area of the earth is approximately 197 million square miles, and IEEE 1584—IEEE Guide for Performing Arc-Flash Hazard Calculations has been covering more of it every day since it was first published almost 11 years ago. Although the IEEE 1584 standard has its roots in the United States, it has gained widespread international use as the most common method for performing arc flash calculation studies. Continue reading
Although beginning with an erratic schedule with revisions to NFPA 70E being spaced anywhere from 2 to 5 years apart, this very important electrical safety standard is now on a regular 3 year revision cycle. In early 2011, I wrote an article about the significant changes that were about to be part of the 9th Edition, the 2012 Edition of NFPA 70E Standard for Electrical Safety in the Workplace. This article will take us a little further into the standard and address some changes that I was not able to include in the previous article. Continue reading
In the earlier years of NFPA 70E and the emergence of arc flash protection requirements, many people would use the NFPA 70E Hazard/Risk Tables to determine what arc rated PPE to wear. This approach continues to shift towards the use of arc flash studies involving incident energy and arc flash boundary calculations based on IEEE 1584. Continue reading
NEC 240.87 has addressed a potentially hazardous situation beginning with the 2011 edition. When selective coordination is critical, e.g., minimizing the extent of an outage, a common design practice is to use a main circuit breaker without an instantaneous tripping function and feeder breakers with one. Without an instantaneous, the main can time delay up to 30 cycles or 0.5 seconds greatly increasing the arc flash hazard. Continue reading