Appendix C: Definitions


Accessible (as applied to equipment).
Admitting close approach; not guarded by locked doors, elevation, or other effective means.

Accessible, Readily. Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.

Approved. Acceptable to the authority having jurisdiction (AHJ).

Arc Blast. Explosive release of molten material from equipment caused by high-amperage arcs.

Arc Flash Hazard. A dangerous condition associated with the possible release of energy caused by an electric arc.

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, arc flash protection boundary, and the appropriate levels of personal protective equipment (PPE).

Arc Rating. 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 calories per centimeter squared (cal/cm2). Breakopen is a material response evidenced by the formation of one or more holes in the innermost layer of flame-resistant material that would allow flame to pass through the material.

Conductive. Suitable for carrying electric current.

Deenergized. 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.

Electrical Hazard. A dangerous condition such that contact or equipment failure can result in electric shock, arc flash burn, thermal burn, or blast injury.

Electrical Safety. Recognizing hazards associated with the use of electrical energy and taking precautions so those hazards do not cause injury or death.

electrically-hazardous. A condition within the Limited Approach Boundary or Arc Flash Protection Boundary where exposed energized electrical conductors or circuit parts are operating per the following energy levels:

  1. 50 Volts or more, with the ability to produce at least 5mA current
  2. Capacitors storing more than 1J (Joules) at 50 Volts or greater; 1000 J at less than 50V.

Electrically Safe Work Condition (see also Verified Deenergized). A state in which the conductor or circuit part to be worked on or near has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if determined necessary.

Enclosed. Surrounded by a case, housing, fence, or wall(s) that prevents persons from accidentally contacting energized parts.

Energized Electrically connected to or having a source of voltage.

Exposed (as applied to energized electrical conductors or circuit parts). Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to electrical conductors or circuit parts that are not suitably guarded, isolated, insulated, or enclosed.

Flame-Resistant (FR). The property of a material whereby combustion is prevented, terminated, or inhibited following the application of a flaming or non-flaming source of ignition, with or without subsequent removal of the ignition source.

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.

Grounded. Connected to ground or to a conductive body that extends the ground connection.

Guarded. 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 or contact by persons or objects to a point of danger.

Incident Energy. 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).

Insulated. Separated from other conducting surfaces by a dielectric (including air space) offering a high resistance to the passage of electric current.

Labeled. 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 inspections of production of labeled equipment or materials, and by whose labeling the manufacturer indicates compliance with appropriate standards of 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.

Listed. Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services and whose listing states that the equipment, material or services either meets appropriate designated standards or has been tested and found suitable for a specific purpose.

Live Parts (see also Energized). Energized conductive components.

Nationally Recognized Testing Laboratory (NRTL. Certain private sector organizations recognized by OSHA as an NRTL. That recognition signifies that the organization has met the necessary qualifications specified in the OSHA NRTL program. The NRTL determines that specific equipment and materials (products) meet consensus-based standards of safety to provide assurance that these products are safe for use in the U.S. workplace.

NEC. The National Electric Code NFPA 70.

Overload. Operation of equipment in excess of normal, full-load rating, or of a conductor in excess of rated ampacity that, when it persists for a sufficient length of time, would cause damage or dangerous overheating. A fault, such as a short circuit or ground fault, is not an overload.

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 Person. One who has skills and knowledge related to the construction, installation, maintenance and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved. Qualified persons are authorized for a specific range of electrical tasks through their JHA and/or AHDs.

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.

Shock Hazard. A dangerous condition associated with the possible release of energy caused by contact or approach to energized electrical conductors or circuit parts .

Verified Deenergized (See Also Electrically Safe Work Condition). A state in which the conductor or circuit part to be worked on or near has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if determined necessary.

Voltage (of a Circuit). The greatest root-mean-square (rms) (effective) difference of potential between any two conductors of the circuit concerned.

Voltage to Ground. For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductors and any other conductor of the circuit.

Working On (energized electrical conductors or circuit parts). Coming in contact with energized electrical conductors or circuit parts with the hands, feet, or other body parts, with tools, probes, or with test equipment, regardless of the personal protective equipment a person is wearing.

 

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