This article provides definitions for various electrical terms that are commonly encountered in the industry. The following terms, their meanings, and relevant standards are essential for understanding electrical systems, equipment, and installations.
For ease of reference, the terms are organized alphabetically, with each definition, including the respective code or standard where applicable.
- Electric-Discharge Lighting
Systems of illumination utilizing fluorescent lamps, high-intensity discharge (HID) lamps, or neon tubing.
(CMP—18) - Electric Power Production and Distribution Network
Power production, distribution, and utilization equipment and facilities, such as electric utility systems that are connected to premises wiring and are external to and not controlled by a system that operates in interactive mode.
(CMP—13) - Electric Sign
A fixed, stationary, or portable self-contained, electrically operated and/or electrically illuminated utilization equipment with words or symbols designed to convey information or attract attention.
(CMP—18) - Electric Supply Stations
Locations containing the generating stations and substations, including their associated generator, storage battery, transformer, and switchgear areas.
(CMP—4) - Electric Vehicle (EV)
An automotive-type vehicle for on-road use, such as passenger automobiles, buses, trucks, vans, neighborhood electric vehicles, and electric motorcycles, primarily powered by an electric motor that draws current from a rechargeable storage battery, fuel cell, photovoltaic array, or other source of electric current.
(CMP—12)
Informational Note: Off-road, self-propelled electric mobile machines, such as industrial trucks, hoists, lifts, transports, golf carts, airline ground support equipment, tractors, and boats are not considered electric vehicles. - Electric Vehicle Connector
A device that, when electrically coupled (conductive or inductive) to an electric vehicle inlet, establishes an electrical connection to the electric vehicle for the purpose of power transfer and information exchange.
(625) (CMP—12) - Electric Vehicle Power Export Equipment (EVPE)
The equipment, including the outlet on the vehicle, that is used to provide electrical power at voltages greater than or equal to 30 Vac or 60 Vdc to loads external to the vehicle, using the vehicle as the source of supply.
(625) (CMP—12) - Electric Vehicle Supply Equipment (EVSE)
Equipment for plug-in charging, including the ungrounded, grounded, and equipment grounding conductors, and the electric vehicle connectors, attachment plugs, personnel protection system, and all other fittings, devices, power outlets, or apparatus installed specifically for the purpose of transferring energy between the premises wiring and the electric vehicle.
(625) (CMP—12) - Electrical Circuit Protective System
A system consisting of components and materials intended for installation as protection for specific electrical wiring systems with respect to the disruption of electrical circuit integrity upon exterior fire exposure.
(CMP—16) - Electrical Datum Plane
A specified vertical distance above the normal high-water level at which electrical equipment can be installed and electrical connections can be made.
(CMP—7) - Electrical Ducts
Electrical conduits, or other raceways round in cross-section, that are suitable for use underground or embedded in concrete.
(CMP—6) - Electrical Life Support Equipment
Electrically powered equipment whose continuous operation is necessary to maintain a patient’s life.
(517) (CMP—15) - Electrical Resistance Trace Heating
Type of protection for the purpose of producing heat on the principle of electrical resistance, typically composed of one or more metallic conductors and/or an electrically conductive material, suitably electrically insulated and protected.
(CMP—14)
Informational Note: See ANSI/UL 60079-30-1 for additional information. - Electrically Connected
A connection capable of carrying current as distinguished from connection through electromagnetic induction.
(668) (CMP—12) - Electrified Truck Parking Space
A truck parking space that has been provided with an electrical system that allows truck operators to connect their vehicles while stopped and to use off-board power sources to operate on-board systems such as air conditioning, heating, and appliances, without any engine idling.
(626) (CMP—12) - Electrified Truck Parking Space Wiring Systems
All of the electrical wiring, equipment, and appurtenances related to electrical installations within an electrified truck parking space, including the electrified parking space supply equipment.
(626) (CMP—12) - Electrolyte
The medium that provides the ion transport mechanism between the positive and negative electrodes of a cell.
(CMP—13) - Electrolytic Cell
A tank or vat in which electrochemical reactions are caused by applying electric energy for the purpose of refining or producing usable materials.
(668) (CMP—12) - Electrolytic Cell Line Working Zone
The space envelope wherein operation or maintenance is normally performed on or in the vicinity of exposed energized surfaces of electrolytic cell lines or their attachments.
(668) (CMP—12) - Electronic Power Converter
A device that uses power electronics to convert one form of electrical power into another form of electrical power.
(CMP—4)
Informational Note: Examples include inverters, DC-to-DC converters, and electronic charge controllers. - Electronically Protected
A motor provided with electronic control that protects the motor against dangerous overheating, overload, and failure to start.
(430) (CMP—11) - Emergency Luminaire, Battery-Equipped
A luminaire with a rechargeable battery, a battery charging means, and an automatic load control relay.
(CMP—13) - Emergency Luminaire, Directly Controlled:
A luminaire that is powered by the facility’s emergency power system, with a control input for dimming or switching, providing emergency illumination upon loss of normal power.
Reference: (700) (CMP—13)
Informational Note: For more details, refer to ANSI/UI 924, Emergency Lighting and Power Equipment, for information covering directly controlled emergency luminaires. - Emergency Power Supply (EPS):
The source(s) of electric power of the required capacity and quality for an emergency power supply system (EPSS).
Reference: (CMP—13) - Emergency Power Supply System (EPSS):
A complete, functioning EPS system connected to conductors, disconnecting means, overcurrent protective devices, transfer switches, and all control, supervisory, and support devices up to the load terminals of the transfer equipment to ensure it operates as a reliable source of emergency power.
Reference: [110:3.3.4] (CMP—13) - Emergency Systems:
Systems that are legally required and classed as emergency systems by relevant authorities. These systems provide emergency illumination, power, or both, to designated areas and equipment in case of failure of normal power supply or in the event of an accident.
Reference: (CMP—13) - Encapsulation «m»:
A type of protection where electrical components that could ignite an explosive atmosphere by sparking or heating are enclosed in a compound, preventing ignition of the explosive atmosphere.
Reference: (CMP—14)
Informational Note: Refer to ANSI/UL 60079-18, Explosive Atmospheres — Part 18: Equipment Protection by Encapsulation «m», for more details. - Enclosed:
Surrounded by a case, housing, or wall(s) that prevents accidental contact with energized parts.
Reference: (CMP—1) - Enclosed-Break:
Devices with electrical contacts that can withstand an internal explosion caused by flammable gas or vapor without suffering damage or transferring the explosion to the surrounding environment.
Reference: (CMP—14)
Informational Note: See ANSI/UL 121201, Nonincendive Electrical Equipment for Use in Hazardous Locations, for additional information. - Enclosure:
The housing or fence surrounding apparatus to prevent accidental contact with energized parts or to protect the equipment from physical damage.
Reference: (CMP—1)
Informational Note: For examples of enclosure types, refer to Table 110.28. - Energized:
Electrically connected to, or is, a source of voltage.
Reference: (CMP—1) - Energized, Likely to Become:
Refers to conductive material that could become energized due to failure of electrical insulation or electrical spacing.
Reference: (CMP—5) - Energy Management System (EMS):
A system that includes monitors, controllers, timers, or other devices to monitor and/or control electrical loads or power production and storage sources.
Reference: (CMP—13) - Energy Storage System (ESS):
A system capable of storing energy and providing electrical energy into the premises wiring system or an electric power production and distribution network.
Reference: (CMP—13)
Informational Notes: - ESS can include batteries, capacitors, and kinetic energy devices like flywheels or compressed air. ESS can also include inverters or converters.
- ESS differs from stationary standby battery installations, where batteries are on a continuous float charge or high charge state.
- Entertainment Device:
A mechanical or electromechanical device designed to provide an entertainment experience.
Reference: (CMP—15)
Informational Note: These devices may include animated props, show action equipment, animated figures, and special effects coordinated with audio and lighting. - Equipment:
A general term for devices, fittings, luminaires, machinery, and related components used in an electrical installation.
Reference: (CMP—1) - Mobile Equipment:
Electrical equipment designed to be moved with mechanical aids or with wheels for movement by individuals or powered devices.
Reference: (CMP—14) - Portable Equipment:
Equipment designed to be moved from one place to another and fed with portable cords or cables.
Reference: (CMP—12) - Signal Equipment:
Includes audible and visual equipment such as chimes, lights, and displays used to convey information to users.
Reference: (CMP—12) - Equipment Branch:
A system of feeders and branch circuits arranged for delayed, automatic, or manual connection to the alternate power source, serving primarily 3-phase power equipment.
Reference: [99:3.3.50] (CMP—15) - Equipment Protection Level (EPL):
A protection level assigned to equipment based on its potential to become a source of ignition in explosive atmospheres.
Reference: (CMP—14)
Informational Note: See ANSI/UL 60079-0 for further details. - Equipment Rack:
A framework designed to support or enclose equipment; can be either portable or stationary.
Reference: (CMP—12)
Informational Note: See EIA/ECA 310-E-2005, Cabinets, Racks, Panels, and Associated Equipment, for examples. - Equipotential Plane:
A system of conductive parts bonded together to reduce voltage gradients in a designated area.
Reference: (CMP—17)
Informational Note: This is an important safety feature in electrical systems to prevent harmful voltage differences. - Essential Electrical System:
A system that ensures continuity of electrical power to critical areas in a healthcare facility during a disruption of normal power. It minimizes disruption within the internal wiring system.
Reference: [99:3.3.52] (CMP—15) - Explosionproof Equipment:
Equipment enclosed in a case that can withstand an explosion of a specific gas or vapor within it, preventing ignition of surrounding gases or vapors.
Reference: (CMP—14)
Informational Notes: - For more details, refer to ANSI/UL 1203, Explosion-Proof and Dust-Ignition-Proof Electrical Equipment.
- See NEMA 250 for explosionproof enclosures that may be marked as Type 7.
- Exposed (Live Parts):
Electrical parts that are capable of being inadvertently touched or approached too closely.
Reference: (CMP—1)
Informational Note: This applies to parts that are not sufficiently guarded, insulated, or isolated. - Exposed (Wiring Methods):
Wiring methods that are on the surface or behind panels designed to allow access.
Reference: (CMP—1) - Exposed (Optical Fiber Cable Exposed to Accidental Contact):
A conductive optical fiber cable positioned such that, if supports or insulation fail, the cable’s conductive parts might contact an electrical circuit.
Reference: (CMP—16) - Exposed Conductive Surfaces:
Surfaces capable of carrying electric current that are unprotected, uninsulated, unenclosed, or unguarded, allowing personal contact.
Reference: [99:3.3.54] (CMP—15)
Informational Note: Paint, anodizing, and similar coatings are not considered sufficient insulation unless listed for such use. - Externally Operable:
Refers to equipment that can be operated without exposing the operator to live parts.
Reference: (CMP—1)
Summary Table
| Term | Definition |
|---|---|
| Electric-Discharge Lighting | Systems using fluorescent, HID lamps, or neon tubing. (CMP—18) |
| Electric Power Production and Distribution Network | Equipment and facilities for power production, distribution, and utilization, external to the system operating interactively. (CMP—13) |
| Electric Sign | Electrically operated/illuminated sign conveying information or attracting attention. (CMP—18) |
| Electric Supply Stations | Locations containing generating stations and substations, including associated equipment. (CMP—4) |
| Electric Vehicle (EV) | Automotive-type vehicle powered primarily by an electric motor, using a rechargeable battery, fuel cell, etc. (CMP—12) |
| Electric Vehicle Connector | Device establishing electrical connection to an electric vehicle for power transfer. (625) (CMP—12) |
| Electric Vehicle Power Export Equipment | Equipment providing electrical power from the vehicle to external loads. (625) (CMP—12) |
| Electric Vehicle Supply Equipment (EVSE) | Equipment for plug-in charging, including conductors and connectors, to transfer energy between premises wiring and the vehicle. (625) (CMP—12) |
| Electrical Circuit Protective System | Protection system for electrical circuits exposed to exterior fire risks. (CMP—16) |
| Electrical Datum Plane | Vertical distance above the normal high-water level for installing electrical equipment. (CMP—7) |
| Electrical Ducts | Conduits or raceways suitable for underground or concrete-embedded installation. (CMP—6) |
| Electrical Life Support Equipment | Electrically powered equipment necessary for maintaining a patient’s life. (517) (CMP—15) |
| Electrical Resistance Trace Heating | Heat-producing protection through electrical resistance. (CMP—14) |
| Electrically Connected | A connection capable of carrying current, distinct from induction. (668) (CMP—12) |
| Electrified Truck Parking Space | Truck parking space with electrical system for off-board power usage. (626) (CMP—12) |
| Electrified Truck Parking Space Wiring Systems | Wiring and equipment related to installations in electrified truck parking spaces. (626) (CMP—12) |
| Electrolyte | Medium providing ion transport in cells. (CMP—13) |
| Electrolytic Cell | Tank or vat for electrochemical reactions to refine or produce materials. (668) (CMP—12) |
| Electrolytic Cell Line Working Zone | Operational zone around exposed energized surfaces of electrolytic cells. (668) (CMP—12) |
| Electronic Power Converter | Device converting electrical power from one form to another. (CMP—4) |
| Electronically Protected | Motor protected by electronic control against overheating, overload, and failure to start. (430) (CMP—11) |
| Emergency Luminaire, Battery-Equipped | Luminaire with rechargeable battery and automatic load control relay. (CMP—13) |
| Term | Definition |
|---|---|
| Emergency Luminaire, Directly Controlled | A luminaire powered by the emergency power system with a control input for dimming or switching during power loss. |
| Emergency Power Supply (EPS) | Source(s) providing the required capacity and quality for an emergency power supply system (EPSS). |
| Emergency Power Supply System (EPSS) | A complete EPS system that ensures reliable emergency power to designated areas. |
| Emergency Systems | Systems providing emergency illumination or power to designated areas in case of power failure. |
| Encapsulation «m» | Protection that prevents ignition of an explosive atmosphere by enclosing electrical parts in a compound. |
| Enclosed | Surrounded by a case or housing to prevent accidental contact with energized parts. |
| Enclosed-Break | Devices designed to withstand internal explosions without transferring the explosion to the external environment. |
| Enclosure | Housing or fence around equipment to prevent contact with energized parts. |
| Energized | Electrically connected to a source of voltage. |
| Energized, Likely to Become | Conductive material that could become energized due to failure of insulation or spacing. |
| Energy Management System (EMS) | A system to monitor and/or control electrical loads or power production/storage sources. |
| Energy Storage System (ESS) | A system capable of storing and providing electrical energy to the wiring system or distribution network. |
| Entertainment Device | A mechanical or electromechanical device providing an entertainment experience. |
| Equipment | General term for devices, luminaires, machinery, and components used in electrical installations. |
| Mobile Equipment | Equipment designed to be moved using mechanical aids or wheels. |
| Portable Equipment | Equipment intended to be moved from place to place, typically fed with portable cords or cables. |
| Signal Equipment | Audible and visual equipment that conveys information to users. |
| Equipment Branch | A system of circuits connected to an alternate power source, serving primarily 3-phase power equipment. |
| Equipment Protection Level (EPL) | Protection level assigned to equipment based on its risk of becoming a source of ignition. |
| Equipment Rack | A framework designed to support or enclose equipment. |
| Equipotential Plane | Conductive parts bonded together to reduce voltage gradients in an area. |
| Essential Electrical System | A system ensuring continuous power to critical areas of a healthcare facility during power disruptions. |
| Explosionproof Equipment | Equipment enclosed to withstand internal explosions without igniting surrounding gases or vapors. |
| Exposed (Live Parts) | Parts capable of being accidentally touched or approached too closely. |
| Exposed (Wiring Methods) | Wiring methods that are on the surface or behind accessible panels. |
| Exposed (Optical Fiber Cable) | Optical fiber cables at risk of accidental contact with an electrical circuit due to support or insulation failure. |
| Exposed Conductive Surfaces | Unprotected surfaces capable of carrying electric current, allowing personal contact. |
| Externally Operable | Equipment that can be operated without contact with live parts. |
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