Dennis Moyer, PE
Electrical quality control, MEP Engineering Inc., Centennial
History tells us that in 1752 Ben Franklin flew a kite in a lightning storm, putting himself and his son, William, at grave risk of electrical shock and death. And yet, Franklin’s approach to this important 18th century experiment may have been practiced with more safety and caution than the safety practices implemented at modern day buildings, in regards to their high-energy electrical panels.
Unfortunately, a vast majority of property managers and owners are foregoing a simple and relatively inexpensive study to ensure that their maintenance team is protected from what would be the equivalent of a lighting blast. The study, which is often referred to as an “arc flash hazard analysis” is only used by 1 percent of property owners throughout the Denver metro area. And while the chances of a killer arc flash occurring is perhaps as minute as being struck by lighting, the risk exists. And, if left unchecked, it could be a very costly one.
Scientifically speaking, an electric arc is a strong discharge of current that jumps a gap in a circuit or between two electrodes. Electric arc flashes produce some of the highest temperatures known to occur on Earth (some can be up to 35,000 degrees Fahrenheit, or 3.5 times the temperature of the surface of the sun).
The intense heat from the arc causes the sudden expansion of air, resulting in a blast with very strong air pressure. All known materials are vaporized at this temperature, and the air blast can spread molten metal to great distances with force.
The “fuses” that can cause arcs aren’t terribly uncommon. Personnel protective equipment should be used while working on energized equipment to help eliminate arcs.
Many things can cause these arc flashes. For example, dust and impurities can provide a path to allow the current to flashover and create arc discharge across the surface. Fumes or vapors can reduce the breakdown voltage of air and cause a dangerous flash. Corrosion of equipment can provide impurities on insulating surfaces, also causing a deadly flash.
Accidental contact with energized-exposed parts can initiate catastrophic arc faults, and accidental dropping of tools may cause momentary short circuit, producing sparks and deadly arcs. And finally, failure of insulating materials can cause equipment to arc and flash.
The cost of having an arc flash hazard analysis performed far outweighs the consequences of a possible tragedy. A professional analysis will provide a property owner and manager with a critical labeling system for each and every part of their electrical system.
The labels will define the energy level for every piece of equipment and the level of personnel protection equipment required to work with or on the specified equipment. It also provides techniques for reducing energy levels and putting in necessary protection devices.
A thorough analysis will make it very clear to a maintenance team where dangerous conditions exist, and when they should consult a professional electrician before opening the cover of a high-voltage electrical panel.
For example, the labeling system will define the following:
Flash hazard boundaries. The distance from exposed live parts in which a person could receive a second-degree burn if an arc flash were to occur.
Flash hazard at a certain distance. Danger levels at certain distances.
System voltage warning. Information that describes when there is a potential risk of a shock hazard.
Limited approach boundary. Unless advised of the possible hazards and escorted by a qualified person, no unqualified person shall be permitted to approach nearer than the limited approach boundary.
Restricted approach boundary. No qualified person shall approach or take a conductive object closer to exposed energized electrical conductors or circuit parts unless the person is insulated or guarded.
In the era of Benjamin Franklin, safety measures such as an arc flash hazard analysis didn’t exist. Fortunately, modern day property owners have this type of analysis at their disposal and can implement it to create a much safer working environment for their maintenance team.
