An arc flash is a dangerous condition associated with the release of energy caused by an electric arc. During an arc flash, uncontrolled current flows through the air when either a phase-to-ground or phase-to-phase short circuit occurs. Arc flash incidents produce some of the highest known temperatures on earth, reaching up to 35,000oF, which is four times the temperature of the sun. This extremely hot flash can affect anything in its path and is powerful enough to vaporize copper at a speed of over 700 MPH.
To date, PowerHawke has conducted and completed more than 50 separate system models representing thousands of individual analysis busses in hospitals, industrial, office and manufacturing facilities throughout New England. So we thought we’d share some insight on what seems to be developing as the key mitigation strategies once an Arc Flash Hazard Analysis has been completed.
Strategy #1: Don’t Work on Energized Systems
We know this sounds pretty obvious, but frankly the best way to deal with this entire topic is to adopt a ‘No Hot Work’ policy – and then enforce it. Years of habits are difficult to change, so getting folks to stop doing something “that they’ve done for years” is a real challenge.
Strategy #2: Install IR Windows
If you are currently engaged in an Electrical Preventive Maintenance Program and are conducting regular Infrared scans of your equipment, you may need to consider adopting other technologies once your Arc Flash Hazard Analysis is completed. We’ve found that locations where we’ve performed IR inspections in the past are now identified with such a high incident energy that opening the device to assess with IR is not possible. Installation of IR windows allows the infrared transmissivity through while protecting the structural integrity of the device.
Strategy #3: Install Voltage Metering
Another outcome of having the knowledge that the incident energy is too high is the case where workers regularly have to open VFD’s and other devices to check voltage or for the absence of voltage when working de-energized. Installation of either non-contact voltage verification ports or actual voltage meters means workers will no longer be exposed to potentially deadly arc flash and blast.
Strategy #4: Change Fuse Type
In a number of cases changing from a standard fuse to a Fast Acting fuse can dramatically change the potential arc flash and incident energy calculations. In other circumstances lowering the fuse capacity can provide another effective mitigation strategy where loads in a system are substantially below the original design criteria. Buildings today undergo so many changes from how they may have been electrically constructed that this option is surprisingly common.
Strategy #5: Change Instantaneous Trip Settings
Years and decades of operation may have afforded ‘adjustments’ to the instantaneous trip setting of you system breakers. Inadvertently, those nuisance adjustments can be a significant source of high incident energy results. One of the least expensive and most practical mitigation techniques remains adjusting the instantaneous – as long as the system performance can handle the adjustment.
Strategy #6: Install Arc Fault Detecting Equipment
Probably the most expensive of what we have described. There are numerous systems from major manufacturers that allow a retrofit of your system that includes an optical sensor that is so sensitive that it will trip your system when it ‘sees’ an arc start in your gear or equipment. In lieu of major change-outs of components in your system, this may be viable in certain cases.