Arc-Flash risk

It is the result of an electrical short circuit in the air. It’s a violent eruption of thermal energy from an electrical source, which can cause severe burns or injuries, even fatal ones. On an electrical panel, Arc Flash risks become a major concern starting from 220 volts.

The difference lies in the severity of the consequences related to the accident. In the case of electrification, it refers to injuries caused by an electric current, whereas electrocution refers to death resulting from an electric shock.

An Arc Flash can reach temperatures between 18 000 and 20 000 °C, approximately three times the surface temperature of the sun.

The risks associated with arc flash exposure are numerous:

• Burns : The heat and flames from a massive explosion can cause third-degree burns. Molten metal splashes can also cause severe burns.
• Hearing loss : The sound wave can reach 165 dB, comparable to that of a jet engine at takeoff, and can lead to hearing degradation or loss.
• Eye injuries : An intense light flash, with UV radiation, can cause eye injuries.
• Respiratory issues : Toxic fumes and vapors (copper vaporization) can cause damage after inhalation.

An Arc Flash can occur in various environments where electrical equipment is present and high electrical currents are used. Here are some examples :

• Factories and industrial facilities : Heavy and complex electrical equipment.
• Electrical substations : High-voltage current transformed into low voltage for distribution.
• Data centers : Large quantities of servers and electrical equipment.
• Commercial facilities : Complex electrical systems.
• Power generation facilities : Power plants : nuclear, hydroelectric, thermal, or wind.
• Construction sites : Temporary equipment and electrical maintenance work.
• Technical rooms and electrical cabinets : Electrical distribution cabinets, circuit breakers, control panels.

It is crucial to follow safety and maintenance protocols to minimize the risk of Arc Flash in these environments.

A Flash Arc can occur when electricity jumps across a gap between two conductors or between a conductor and a conductive surface (such as the ground or a metal enclosure). Several conditions can lead to an Arc Flash :

• Short circuit : A short circuit between two conductors can create an electric arc. This short circuit can be caused by improperly used tools, exposed wires, damaged insulation, or conductive objects falling into electrical equipment.
• Accidental contact : Accidental contact of a tool or another object with live conductors can cause an arc flash (such as the dropping of tools or accidental contact with electrical systems). This can happen during maintenance or repair work. An Arc Flash can occur with or without human presence.
• Insulation failures : Failures or degradation of the insulation around electrical conductors can allow electricity to jump through the air, resulting in an Arc Flash.
• Accumulation of dust or debris : Dust, debris, or metallic contaminants can accumulate on conductive surfaces, creating conductive paths that promote electrical arcs.
• Corrosion : Corrosion of conductors or connections can increase electrical resistance and generate heat, which can trigger an Arc Flash.
• Moisture : Moisture or condensation can create a conductive path between conductors, facilitating the formation of an arc.
• Overvoltage or overcurrent : Surges or excessive currents, due to equipment failure or lightning, for example, can cause an arc flash by overheating components and creating short circuits.
• Improper handling of equipment : Incorrect opening or closing of switches, breakers, or other energized equipment can generate arcs.

From 220 Volts.

One might think that in LV, there is no exposure to an Electrical Arc,, but that is false ! Even in ELV, the risk is present.

The determining factor is the current intensity, more than the network voltage.

There are several :

• The intensity of the electrical arc, taking into account :
  • Network voltage
  • Current intensity / Amperage
  • Inter-electrode gap
  • Confined environment
• The duration of the electrical arc : or the exposure time
• Working distance : proximity to the source of the Flash Arc
• Improperly worn PPE : improper use of PPE can exacerbate the risks

It is necessary for several reasons, as follows :

• It helps define the protection level of the garment
• It helps define the protection class (4KA, 7KA, etc.)
• It determines the ATPV level for a given electrical installation

Only a notified laboratory or authorized personnel are allowed to carry out the risk analysis.

The unit of measurement used is Cal/cm².

No, there is no formula or normative text on the subject.