What is an Arc Flash?
- A dangerous release of energy created by an electrical fault
- Release will contain:
- Thermal energy
- Acoustical energy
- Pressure wave
- Debris
What Causes an Arc Flash?
- The arc can be generated by:
- Mechanical breakdown / failure
- Current overload
- Accidental contact
Arc Flash Intensity
- Variables that effect the size and energy of an electric arc flash are:
- Amperage
- Voltage
- Arc Gap
- Closure time
- Distance away from arc
- 3 phase v single phase
- Confined space
What Type of Equipment Can Cause an Arc Flash?
- Typical equipment can be:
- Motor Control Centers (MCC’s)
- Circuit Breakers
- Disconnects
- Metering Devices (remove - install)
- Panel Boards
- Switchgear (low and high voltage)
- Transformers
Arc Energy Basics
- Exposure energy expressed in cal/cm2
- ½ to 1 cal/cm2 = hottest part of lighter in 1 sec
- An exposure of only 1-2 calories will cause second degree burn on human skin
- Typical non-FR workwear can ignite at energies as low as 2 calories
- Reports indicate that 80-90% of job tasks have hazards with the potential to release up to 8 cal/cm2
Arc Flash Events
- Arc temp can reach 35,000 F
- Copper expands 67,000 times when vaporized
- Fatal burns can and do occur at >10 feet
- Per OHSA, 80% of electrically related accidents, incidents and fatalities among qualified workers are caused by - Arc Flash
