Arc Flash Hazard – A source of possible injury or damage to health associated with the release of energy caused by an electric arc.
The maximum incident energy resistance demonstrated by a material (or a layered system of materials) prior to breakopen or at the onset of a second-degree skin burn. Arc rating is normally expressed in cal/cm².
Arc Flash Suit – A complete arc-rated clothing and equipment system that covers the entire body, except for the hands and feet.
Arc Rating (AR) – The value attributed to materials that describe their performance to exposure to an electrical arc discharge. The arc rating is expressed in cal/cm² and is derived from the determined value of the arc thermal performance value (ATPV) or energy of break open threshold (EBT) (should a material system exhibit a break open response below the ATPV value). Arc rating is reported as either ATPV or EBT whichever is the lower value.
Balaclava – An arc-rated head-protective fabric that protects the neck and head except for a small portion of the facial area.
Barrier – A physical obstruction that is intended to prevent contact with equipment or energized electrical conductors and circuit parts.
Boundary, Arc Flash – When an arc flash hazard exists, an approach limit from an arc source at which incident energy equals 1.2 cal/cm² (5 J/cm²).
Boundary, Limited Approach – An approach limit at a distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists.
Boundary, Restricted Approach – An approach limit at a distance from an exposed energized electrical conductor or circuit part within which there is an increased likelihood of electric shock, due to electrical arc-over combined with inadvertent movement.
Free from any electrical connection to a source of potential difference and from electrical charge; not having a potential different from that of the earth.
Disconnecting Means – A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply.
A dangerous condition such that contact or equipment failure can result in electric shock, arc flash burn, thermal burn, or blast.
Recognizing hazards associated with the use of electrical energy and taking precautions so that hazards do not cause injury or death.
Electrical Single-Line Diagram
A diagram that shows, by means of single lines and graphic symbols, the course of an electric circuit or system of circuits and the component devices or parts used in the circuit or system.
Electrically Safe Work Condition (ESWC) – A state in which an electrical conductor or circuit part has been disconnected from energized parts, locked/tagged out in accordance with established standards, tested to verify the absence of voltage, and, if necessary, temporarily grounded for personnel protection.
Electrically connected to or having a source of voltage.
Exposed (as applied to live parts)
Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts that are not suitably guarded, isolated, or insulated.
The property of a material whereby combustion is prevented, terminated, or inhibited following application of a flaming or non-flaming source of ignition, with or without subsequent removal of the ignition source. Flame resistance can be an inherent property of the material, or it can be imparted by a specific treatment applied to the material.
A dangerous condition associated with the release of energy caused by an electric arc.
Flash Hazard Analysis
A study investigating a worker’s potential exposure to arc-flash energy, conducted for the purpose of injury prevention and the determination of safe work practices and the appropriate levels of PPE.
Flash Protection Boundary
An approach limit at a distance from exposed live parts within which a person could receive a second degree burn if an electrical arc flash were to occur.
The amount of energy impressed on a surface, a certain distance from the source, generated during an electrical arc event. One of the units used to measure incident energy is calories per centimeter squared (cal/cm²).
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.
Equipment or materials to which has been attached a label, symbol, or other identifying mark of an organization that is acceptable to the authority having jurisdiction and concerned with product evaluation, that maintains periodic inspection of production of labeled equipment or materials, and by whose labeling the manufacturer indicates compliance with appropriate standards or performance in a specified manner.
Limited Approach Boundary
An approach limit at a distance from an exposed live part within which a shock hazard exists.
Lockout/Tagout (LOTO) – Specific practices and procedures to safeguard employees from the unexpected energization or startup of machinery and equipment, or the release of hazardous energy during service or maintenance activities
Prohibited Approach Boundary
An approach limit at a distance from an exposed live part within which work is considered the same as making contact with the live part.
Qualified Electrical Auditor – A qualified electrical worker who has been authorized to perform audits on other qualified electrical workers.
One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved.
Qualified Worker – One who has demonstrated skills and knowledge related to the construction and operation of electrical equipment and installations and has received safety training to identify the hazards and reduce the associated risk.
Restricted Approach Boundary
An approach limit at a distance from an exposed live part within which there is an increased risk of shock, due to electrical arc over combined with inadvertent movement, for personnel working in close proximity to the live part.
Risk – A combination of the likelihood of occurrence of injury or damage to health and the severity of injury or damage to health that results from a hazard.
Risk Assessment – An overall process that identifies hazards, estimates the likelihood of occurrence of injury or damage to health, estimates the potential severity of injury or damage to health, and determines if protective measures are required.
Shock Hazard – A source of possible injury or damage to health associated with current through the body caused by contact or approach to exposed energized electrical conductors or circuit parts.
Single (One) Line Diagram – A diagram that shows, by means of single lines and graphic symbols, the course of an electric circuit or system of circuits and the component devices or parts used in the circuit or system.
Step potential – A ground potential gradient difference that can cause current flow from foot to foot through the body.
Touch potential – A ground potential gradient difference that can cause current flow from hand to hand, hand to foot, or another path, other than foot to foot, through the body.
Touch/Step potential – A ground potential gradient difference that can cause current flow from hand to foot through the body.
A person who is not a qualified person.
Unqualified Worker – A person who is not a qualified worker, but is still required to be trained to avoid the electrical hazard.
Voltage, Nominal – A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts).