Electrical Safety, Chapter 1

incident energy analysis

A component of an arc flash risk assessment used to predict the incident energy of an arc flash for a specified set of conditions.

arc flash hazard

A dangerous condition associated with the possible release of energy caused by an electric arc

electrical hazard

A dangerous condition in which contact or equipment failure can result in electrical shock, arc flash burn, thermal burn, or a blast.

Occupational Safety and Health Administration (OSHA)

A federal government agency which requires employers to provide a safe work environment for their employees.

National Fire Protection Association (NFPA)

A national organization that develops codes and standards related to fire, electrical, and life safety.

International Electrotechnical Commission (IEC)

A nonprofit organization that sets standards for electromechanical equipment in most of the world.

automated external defibrillator (AED)

A portable electronic device capable of interpreting a person's heat rhythm and automatically delivering a defibrillating shock to stop an irregular heart rhythm, there by allowing the heart to reestablish a normal rhythm.

National Electrical Code (NEC)

A standard on practices for the design and installation of electrical power systems, circuits, and components.

arc rating

A value attributed to a material that describes the performance of the material during exposure to an electrical arc discharge.

NFPA 70E

A voluntary standard for electrical safety-related work practices.

arc flash boundary

An approach limit at a distance from a prospective arc source within which a person could receive a second-degree burn if an electrical arc flash were to occur.

limited approach boundary

An approach limit at a distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists.

arc-rated clothing

Meets ASTM F1506 or other standards that have similar requirements.

arc blast

Occurs when a pressure wave is created by the rapid heating of gases within the arc column, as well as vaporizing metal.

electrical shock

Occurs when a worker comes in contact with an energized conductor or circuit part.

automated external defibrillator (AED)

Passes an electrical current through the heart, causing the heart muscle to contract and briefly stop.

upstream overcurrent protective device

Refers to a circuit breaker, fuse, protective relay, or switch that is closer to the main incoming power, which is often the utility power. Based on its position on single-line diagram and relation to the flow of power from the utility.

incident energy

Two main components: convective heat, which is heat flow through air, and radiant heat, which is heat energy that is transmitted by electromagnetic waves.

risk assessment

Two types: shock and arc- flash identified in NFPA 70E.

arc flash

Typically occur when a conductive object makes contact between an energized conductor or circuit part and ground.

restricted approach boundary

An approach limit at a distance from an exposed energized electrical conductor or circuit part within which there is an increased risk of shock, due to electrical arc-over combined with inadvertent movement, to personnel working in close proximity to the energized electrical conductor or part. Only qualified person can cross this boundary. An unqualified person, even if continuously escorted, cannot enter this space.

risk

An estimate of the combination of the likelihood of the occurrence of a hazardous event or exposure and the severity of injury or illness that may result from the event or exposure.

arc flash

An extremely high temperature discharge produced by an electrical current that flows through the air, usually to ground.

qualified person

An individual who has received training and demonstrated skills and knowledge in the construction and operation of electric equipment and installations as well as the hazards involved.

risk assessment

An overall process that identifies hazards, estimates the potential severity of injury or damage to health, and determines if protective measures are required.

Personal Protective Equipment (PPE)

Clothing and/or equipment worn by an employee to reduce the possibility of injury in the work area.

guarded

Describes any equipment that is covered, shielded, fenced, enclosed, or otherwise protected by means of suitable covers, casings, barriers, rails, screens, mats, or platforms to remove the likelihood of approach to a point of danger or contact by persons or objects.

downstream overcurrent protective device

Refers to a circuit breaker, fuse, protective relay, or switch that is further from the main incoming power, which is often the utility power. Based on its position on single-line diagram and relation to the flow of power from the utility. Below the utility but could also be upstream of other devices below or to the left on a single-line diagram.

Three recognized electrical hazards

Shock, arc flash, and arc blast.

incident energy

The amount of energy impressed on a surface, a certain distance from the source, during an electrical arc event.

arc thermal performance value (APTV)

The incident energy of a material or multilayer system of materials that results in a 50% probability that sufficient heat transfer through the tested specimen will cause a second-degree burn injury based on the Stoll curve, expressed as kW/M² (cal/cm²).

material brakeopen

The incident energy where clothing chars, crumbles, and falls apart, which allows flames an heat to penetrate.