EN 61482-1-2: Box Test Method and “Ka” explained 

The arc box test, also known as the arc resistance or arc tracking test, is a standardized method evaluating electrical equipment and materials under electrical arc conditions. It’s a vital test for ARC flash protection in Europe. Conducted by placing a sample in a box filled with air and steam, an electrical arc is generated, observing the material for signs of damage or degradation.

This test assesses a material’s resistance to arcing and its ability to prevent flame spread during electrical faults, commonly applied to plastics, rubber, and polymers for electrical insulation.

Results are reported in seconds a sample withstands the electrical arc before failure and any observed damage. This informs material selection for electrical equipment, ensuring safety and reliability.

The “kA” unit quantifies fault current, crucial for arc flash analysis and electrical safety. An arc flash, emitted during a fault current in an electrical system, poses risks to people and equipment. Fault current, often in kiloamperes (kA), informs incident energy calculations, crucial for hazard analysis. Expressed in kA (thousands of amperes), understanding fault current aids in implementing safety measures for worker and equipment protection.

What does “Ka” mean?

The “kA” unit quantifies electrical fault current, crucial in arc flash analysis and electrical safety. An arc flash, generated during a fault current flow in an electrical system, emits intense heat and light, posing risks to people and equipment.

To assess arc flash hazards, determining available fault current in amperes (A) is key. This metric, often in kiloamperes (kA), informs incident energy calculations, measuring thermal energy per unit area (J/cm²). Incident energy varies with factors like fault current, duration, and distance from the arc.

Expressed in kA, “kA” represents thousands of amperes. For instance, a 20 kA fault current implies 20,000 amperes at a location. Understanding fault current aids in arc flash hazard analysis, guiding safety measures for worker and equipment protection.

EN 61482-1-2 garments are certified to two levels, Arc Protection Class (APC) 1 and 2.

APC 1 protects against 4Ka 

APC 2 protects against 7Ka

What Is An Arc Flash?

An arc flash is a sudden release of electrical energy that occurs when current jumps across a gap between two conductors or from a conductor to a ground. The arc flash generates an intense burst of heat and light that can cause serious injuries, damage to equipment, and fires.

Arc flashes can occur in a wide range of electrical systems and equipment, including switchgear, transformers, motors, and other high-voltage components. They can be caused by a variety of factors, including equipment failure, human error, or a short circuit.

The intense heat generated by an arc flash can cause severe burns, as well as ignite clothing and other materials in the surrounding area, leading to secondary fires. The bright light from the arc flash can also cause temporary or permanent vision damage.

To prevent arc flash incidents, it’s important to follow proper electrical safety procedures, including wearing appropriate personal protective equipment (PPE), de-energizing equipment before working on it, and maintaining a safe distance from energized equipment.

Understanding Arc Ratings and Calories

Now that you understand FR clothing is tested and given an arc rating, you know that the arc rating measures the amount of heat the flame resistant fabric blocks when exposed to electric arc. The arc rating is the number of calories that the garment is expected to “absorb” if exposed to an electric arc. Arc rating is, in essence, the level of protection provided to you, the wearer.

Calorie is the unit of measure of the heat energy of an arc flash and the protective level of FR clothing. The bigger the calorie number, the greater the heat energy level of arc flash and the greater the protective level of the clothing. You will be protected from an electric arc if your clothing has a higher calorie arc rating than the calories of heat generated by the arc.

While it does not matter if the fabric has an Ebt,  ATPV and or ELIM value, it is important to pay attention to the calorie level the fabric can support* (as expressed in cal/cm2)