Key Terms

Fault Current: The amount of current delivered at a point on the system during a short-circuit condition.

Fault Current, Available: The largest amount of current capable of being delivered at a point on the system during a short-circuit condition.

In 2021, NFPA added the following informational notes regarding available fault current:

• Informational Note No. 1: A short circuit can occur during abnormal conditions such as a fault between circuit conductors or a ground fault.
• Informational Note No. 2: If the DC supply is a battery system, the term available fault current refers to the prospective shot-circuit current.
• Informational Note No. 3: The available fault current varies at different locations within the system due to the location of sources and system impedances.

Ground Fault: An unintentional, electrically conductive connection between an ungrounded conductor of an electrical circuit and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.

Grounded (Grounding) Connected (connecting) to ground or to a conductive body that extends the ground connection.

Incident Energy: The amount of thermal energy imposed on a surface, a certain distance from the source, generated during an electrical arc event.

Qualified person: For the purposes of this course, a qualified person is someone that has the proper skills and knowledge related to the construction, maintenance, or operation of electrical equipment and installations. A qualified person must be familiar with and demonstrate an ability to use the following:

• Special precautionary techniques
• PPE
• Insulation and shielding materials
• Insulated tools and testing equipment

Training: Must include the following:

• The skills to identify the electrical hazards and reduce the associated risk
• The skills to distinguish exposed live parts from other parts of electrical equipment
• The skills to determine the nominal voltage of exposed live parts
• The clearance distances specified in 1910.333(c) and the corresponding voltages to which the qualified person will be exposed

Short circuit: A scenario where the current leaves its intended pathway and completes the circuit through an alternative route, such as through a piece of metal, a part of the body, or the air.

Working distance: The distance between a person's face and chest area and a perspective arc source.

To learn more about Arc Flash Safety visit our OSHA Construction Arc Flash Safety Online Training web page.