What is Electric Arc Flash?
Electric arc flash is one of the most serious and least understood electrical hazards. An electric arc (sometimes referred to as “electrical flashover”) is a continuous electric discharge of high current which flows through an air gap between conductors. This generates a very bright ultra-violet light as well as intensive heat. An arc flash is typically caused by a short circuit. This is sometimes due to a technical failure of electrical equipment (e.g. improper installation, dust, corrosion, surface impurities and sometimes simply due to normal wear and tear). However, in the majority of cases, short circuits are the result of a human error (e.g. caused by a worker touching a test probe to the wrong surface or from a slipped tool).
WHAT ARE THE CONSEQUENCES OF ELECTRIC ARC FLASH?
Depending on the severity of the arc flash, a function of arc current and the duration of the arc, and dependant on the distance from the arc, it can lead to:
- High heat of the electric arc up to 20,000 °C – causing burns to the skin and body of the worker
- Fire - causing potential injury to the worker as well as damage to the surrounding place of work
- An arc blast (electric arc explosion) with a blast pressure of up to 1000 kg /m2 which expels molten metal particles, remnants of destroyed equipment and related components at high speed - causing injury to the worker
- Sound blast (up to 140dB – as loud as a gun) - causing auditory damage to the worker
- Ultra-violet light from the blast – resulting in damage to the eyesight of the worker
The consequences for people working on or close to energized electric equipment will primarily depend on the amount of Incident Energy received at the body surface, which depends on its distance from the arc. The primary concern for the exposed person is skin burns.
WHEN DOES ELECTRIC ARC FLASH OCCUR?
Electric arc flash can occur whenever and wherever electrical equipment is live. During maintenance or repair, if for any reason the equipment cannot be made “dead”, then an electric arc can occur.