Some Frequently Asked Questions on Arc Protection

What is an arc flash?

An arc flash is an electrical explosion caused by a low impedance earth or another phase in the electrical system. High temperatures can lead to rapid heating of the surrounding air and extreme pressure, resulting in an arc explosion. An arc blast (the result of an arc flash) may vaporise all solid copper conductors, which will expand to 67,000 times their original volume as they evaporate.

The arc blast releases flames, bright lights and pressure waves that create a flying shrapnel explosion. Arc flashes occur without warning. This usually results in the complete destruction of the equipment involved and causes serious injury or death to persons within the arc flash boundary in the event of an accident.

The energy released by an arc flash is a function of the system voltage, the available fault current at that location and the duration of the arc.

Should you be concerned about arc flash hazards on low voltage equipment?

The theory that the arc flash hazard is greater at higher voltages is a common misconception. For low voltages (e.g. 480v), it is more common for the arc flash hazard level to be higher because of the higher fault current. Most recorded arc flash accidents occur at lower voltages because the fault is caused by a technician working on electrical equipment. Due to the long clearing times of the protective devices and the high fault currents, it is not uncommon to have a category 3 or 4 arc flash hazard on low voltage systems.

What causes an arc flash?

When a large amount of fault current flows through multiple conductors in very close proximity to each other, the potential difference will, among other factors, ionise the air, thus creating a low resistance path between the conductors. Incorrect tools, incorrect electrical equipment, corrosion of electrical equipment, incorrect working techniques, lack of electrical safety training and lack of preventative maintenance are just some of the events that make arc flash more likely to occur.

What kind of damage can an arc flash cause?

It is estimated that between 5 and 10 arc flashes and explosions occur in electrical equipment every day in the United States, and that 2,000 people are admitted to burn centres each year with severe burns.

The degree of injury is directly related to the power of the arc flash, the distance of the person during the arc flash and the protective equipment (PPE) worn by the individual during the arc flash.

Burns, concussion, lung failure, hearing loss, shrapnel damage and fractures are common injuries due to the force of the energy blast and high heat.

What are the costs associated with an arc flash accident?

The total cost of the arc flash incident is estimated to be between $12 and $15 million, including medical costs, downtime, equipment replacement, litigation, and insurance and litigation costs.

How do I determine the correct level of PPE?

In order to select the right PPE (Personal Protective Equipment), it is important to know the incident energy at each point where workers may need to work on energised equipment. These calculations are determined in an arc flash study and need to be carried out by a qualified person (e.g. an electrical engineer).

A comprehensive view of the above issues, Wuxi Deep-protection still recommends that we combine the actual situation to purchase anti-arc equipment, never reduce the risk of injury to personnel.