ME Electrician key terms

A protective device that constantly compares current leaving a circuit with current returning and trips quickly when a small imbalance suggests current is leaking to ground through a person or equipment.

A circuit breaker or receptacle device designed to detect the signature current and voltage patterns of dangerous parallel or series arcing and to open the circuit before the arc ignites surrounding material.

The conductor that connects the non-current-carrying metal parts of equipment to the system grounding point so that a fault creates a low-impedance path and quickly opens the overcurrent device.

The conductor that links the grounded circuit conductor or equipment grounding system to the grounding electrode, sized according to the electrode type and the service or feeder conductors it serves.

A conductive object such as a ground rod, concrete-encased electrode, metal water pipe, or ground ring that provides a direct connection to the earth for the grounding system.

All grounding electrodes at a building or structure that must be bonded together into one interconnected system, including metal underground water pipe, structural steel, concrete-encased electrode, ground ring, and made electrodes.

A conductor that ensures electrical continuity between metal parts that must be electrically connected, such as service equipment enclosures, metal raceways, or the grounding electrode system components.

The connection in service equipment that ties the grounded service conductor to the equipment grounding bus, establishing the single point where the grounded system and equipment grounding system meet.

The circuit conductor that is intentionally connected to earth at the service, commonly the neutral, which carries return current under normal operation and is white or gray in color.

Any device such as a fuse or circuit breaker that automatically opens a circuit when current exceeds its rating for a set time, protecting conductors and equipment from overheating.

Operation of equipment beyond its normal full-load rating or a conductor carrying more than its ampacity, producing gradual heating that an overcurrent device is intended to interrupt before damage occurs.

An accidental low-impedance connection between two circuit conductors of different potential, causing very high current flow that must be cleared rapidly by the overcurrent protective device.

Unintended contact between an energized conductor and ground or grounded metal, which can energize equipment frames and is the condition GFCI devices are designed to detect and interrupt.

The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating, after any correction or adjustment factors are applied.

The required reduction of conductor ampacity when more than three current-carrying conductors are installed together in a raceway or cable, because mutual heating limits how much current each can safely carry.

An enclosed channel of metal or nonmetallic material designed expressly for holding wires, cables, or busbars, such as conduit, tubing, or wireways, and subject to fill and support rules.

The calculated volume of a box required to safely contain conductors, devices, fittings, and equipment grounding conductors, based on conductor sizes and the volume allowance per conductor.

An enclosure where conductors are spliced or where raceways or cables meet, which must be accessible and sized so that splices and devices fit without crowding or damage to insulation.

The required clear floor space in front of electrical equipment, including depth, width, and height, kept free of obstructions so a person can safely work on energized or de-energized equipment.

The equipment at the supply end of a premises wiring system that contains the main disconnecting means and overcurrent protection, and is the location of the main bonding jumper.

All circuit conductors between the service equipment or source of a separately derived system and the final branch-circuit overcurrent device, sized to carry the total load it supplies.

The circuit conductors between the final overcurrent device protecting the circuit and the outlets or utilization equipment it serves, classified as general purpose, appliance, or individual.

A ratio applied to the total connected load to account for the fact that not all loads operate at once, allowing service and feeder conductors to be sized smaller than the sum of all loads.

The reduction in voltage along a circuit caused by conductor resistance and reactance, which can cause poor equipment performance and is limited by recommended conductor sizing practices.

The relationship stating that voltage equals current multiplied by resistance, used to calculate expected current, voltage, or resistance in a circuit and to verify measurements during troubleshooting.

A circuit with only one path for current, so the same current flows through every component and the total resistance is the sum of the individual resistances, with voltage dividing across loads.

A circuit with multiple current paths in which the same voltage appears across each branch, total current is the sum of branch currents, and total resistance is less than the smallest branch resistance.

The ratio of real power in watts to apparent power in volt-amperes in an alternating-current circuit, reflecting how much of the supplied power performs useful work.

Electric current that reverses direction periodically, typically 60 hertz in North American power systems, producing the changing magnetic fields that transformers and motors rely on.

A device that transfers electrical energy between circuits through magnetic induction, raising or lowering voltage while keeping power roughly constant, and creating a separately derived system when used as a source.

A premises wiring system whose power comes from a source such as a transformer or generator with no direct electrical connection to supply conductors, requiring its own grounding and bonding.

A safety procedure in which an energy-isolating device is locked and tagged to prevent accidental energization while work is performed, with only the person applying the lock removing it.

A dangerous release of energy caused by an electric arc between conductors or to ground, producing intense heat, light, and pressure that can severely burn or injure workers nearby.

Clothing and gear such as insulated gloves, arc-rated clothing, and face protection worn to reduce injury from electrical, thermal, and physical hazards while performing electrical work.

A Maine license authorizing the holder to perform and supervise electrical work, contract for electrical installations, and in some cases employ or supervise journeyperson and apprentice electricians.

A Maine license allowing the holder to perform electrical installations under the direction of a master electrician or licensed electrical contractor, after meeting experience and examination requirements.

A person registered with the State to learn the trade while working under required supervision, accumulating on-the-job hours and related instruction toward journeyperson eligibility.

A Maine license held by a business entity that permits it to engage in the business of electrical installation, requiring a designated master electrician responsible for the work performed.

The periodic training hours a licensed electrician must complete to renew a Maine license, covering code updates and safety topics and documented to the Board at renewal.