7.10.2020

Electrical Arc Flash – Dangers and Protection

It is well known that one of the most important hazards, that is a main source of very serious electrical accidents, is related to the excistence of electric arc in the electromechanical equipment.

More specifically, the electric arc is possible when performing tasks that require stoping and starting the main voltage. It happens when two electrodes that are in contact with each other in such way that a low amperage electric current flows though, get a few millimeters apart. When that happens a spark is generated. That spark gets stabilized when the voltage remains at the appropriate level (40-45 Volts) and at the same time the gas that is situated between the electrodes acts like a bridge ensuring constant flow of electric current.

Depending on the intensity of the electric arc, the dangers that may appear are:

• High temperature that can reach 1600°C, resulting to the melting of most of the materials in a typical installation.
• Explosive forces – shock wave
• Very loud noise
• Very intense flash that include UV
• Plasma release
• Toxic smoke and fumes
• Solid residue at very high speed

There are multiple consequences for an employee in such a situation. Burns, blindness, hearing loss, chest damage(from the electric shock) and extensive injuries that on their totality and severity can lead to death.

It is undeniable that it is extremely important to have all the collective and individual measures in place to effectively eliminate the dangers of the electric arc. To combat the effects it is very important to have the means for individual protection such as protective gear, gloves, head protection, mask and suitable footware that can offer the higher safety level for the employee when they are handling and maintaining electromechanical equipment.

In that regard it becomes clear that the sourcing of the protection gear must come with the required credentials e.g. certification according to european standards and requirements indicated by the CE marking and instructions for safe use from the manufacturer.

Specifically with the protective clothing against the electric arc, an important aid is the establishment of international and european standards according to IEC and EN respectively. These determine the set of specifications and restrictions.

The IEC 61482-1-2 standard and the respective european ΕΝ 61482-1-2, examine thoroughly the testing procedures the materials and final protective apparel must withstand.

It is worth noting that all the technical assessment studies coping with electrical accidents deal with the calculation and the specification of the incident energy of the electric arc (cal/cm^2) at different work positions in front of the electromechanical equipment in conjunction with the real operating conditions.

The most used tools for the incident energy calculation at these events are the IEEE 1684 and NFPA 70E standards.