What is an electrical arc flash?

An electrical arc flash is a huge amount of energy caused at a switchgear. These highly volatile and dangerous explosions can result in tens of thousands of pounds of damage, long periods of downtime and even loss of life.

 

How does an electrical arc flash occur?

Electrical arc flashes are usually caused by accident. It can be the result of a member of staff dropping a tool during maintenance, or can be down to a rodent, snake or even water entering the enclosure.

Arc flashes can also occur as a result of poor maintenance of facilities and equipment.

 

What exactly is an electrical arc flash?

An arc flash occurs when a current flows through ionised air (air that is conducting). The result is a powerful explosion of energy in the form of heat, light and high-pressure waves. This explosion will vaporise all switchgear components, with temperatures reaching 20,000°c. Should an employee be within a close proximity of the arc flash, likely injuries include severe burns, damaged hearing and sight, impalement from flying shrapnel.

These stages of events take place over a very short amount of time. The table below highlights the 4 main stages of an arc flash:

10-30ms
(Compression stage)
Ignition of current flow through ionised air
Rapid release of energy
Maximum pressure
30-50ms
(Expansion stage)
Shock/pressure wave (up to 4 bars)
Sound wave
50-100ms
(Emission stage)
20,000°c temperatures
100-300ms
(Thermal or ‘burn through’ stage)
Toxic gases
Steel and copper fire
Hot shrapnel

Staff and equipment are left unprotected if arc flash protection isn’t in place.

 

Prevention of electrical arc flashes

The Arcteq arc protection system offers both detection and the ’cure’ to arc faults. By detecting and eliminating the arc quickly, it prevents serious injury to staff and assists in limiting damage to just one area.

The AQ100 arc flash relay detects the light, current or pressure produced by an arc fault and is able to trip the circuit breaker nearest to the fault, cutting the current. The AQ1000 arc quenching system will create a three-phase low impedance parallel path for the fault current, drawing the arc fault into the quenching unit, extinguishing the arc rather than letting it extend into the switchgear.