Red Seal Construction Electrician key terms

A written procedure in which each energy source feeding equipment is isolated, locked, and tagged by the worker doing the work, then verified as de-energized before anyone touches conductors.

The distance from exposed live parts within which a person could receive a second-degree burn from an arc flash, calculated from incident energy and used to set approach limits and PPE.

The amount of thermal energy per unit area that reaches a surface at a stated working distance during an arc flash, usually expressed in calories per square centimetre or joules per square centimetre.

The assumed distance from the worker's chest or face to the prospective arc source, used in arc flash calculations and printed on equipment labels to interpret incident energy values.

A shock-protection distance around exposed live parts inside which only qualified persons, or unqualified persons escorted by a qualified person, may go; it depends on voltage and whether the part is movable.

A closer shock-protection boundary where a qualified person must use shock protection, such as insulated tools or gloves, and must be accompanied, because the risk of electric shock rises sharply.

A worker who has demonstrated the skills and knowledge needed to safely construct, install, inspect, or work on electrical equipment, including recognizing and avoiding the hazards involved.

The practice of verifying with a known-good voltage tester that conductors and equipment are de-energized, and re-verifying the tester afterwards, before hands or tools contact them.

An instrument used to confirm the presence or absence of voltage on a conductor; its rating must exceed the system voltage, and its operation should be proven on a known live source before and after each test.

The relationship stating that voltage equals current multiplied by resistance; rearranged, it lets you find current from voltage and resistance or resistance from voltage and current in a circuit.

The ratio of real power in watts to apparent power in volt-amperes in an alternating-current circuit; a value below one means current and voltage are out of phase, so more current is needed for the same useful work.

The product of root-mean-square voltage and current in an alternating-current circuit, measured in volt-amperes, which sets conductor and equipment sizing even when real power is lower.

The reduction in voltage along a circuit caused by conductor impedance; it grows with current, length, and conductor resistance and must be limited so equipment at the far end receives adequate voltage.

The ratio of the maximum demand on a system to the total connected load; it allows service and feeder sizing based on realistic simultaneous use rather than every load running at once.

The sum of the nameplate ratings of all equipment that could be supplied by a service or feeder, used as the starting point before demand factors and diversity are applied.

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

Reducing a conductor's allowable ampacity to account for conditions such as high ambient temperature or many current-carrying conductors bundled in one raceway, using factors from the code tables.

A check that the total cross-sectional area of conductors, including insulation, does not exceed the permitted percentage of a raceway's interior area, keeping pulling tension and heat within limits.

The minimum radius to which a cable or raceway may be curved without damaging insulation or kinking the raceway; it is usually stated as a multiple of the cable or conduit diameter.

A raceway component that slides to absorb length changes caused by temperature swings, preventing buckling or pulled joints in long outdoor or exposed conduit runs.

A conductor that intentionally connects metal parts to form a low-impedance path so they stay at the same potential, preventing dangerous voltage differences and carrying fault current reliably.

The conductor that connects the system grounded conductor or equipment grounding conductor to the grounding electrode, providing a path to earth for lightning, surges, and certain faults.

An area where conductive surfaces are bonded together so that voltage differences across it are minimized, commonly used around pools, spas, and livestock watering areas to reduce shock risk.

An unintentional connection between an energized conductor and earth or bonded metal, which can create shock hazard and must be cleared quickly by overcurrent devices or ground-fault protection.

A device that compares current leaving and returning on a circuit and trips when the imbalance indicates leakage to ground, protecting people from shock in wet or damp locations.

The point where utility conductors enter a building, including the service drop or lateral, meter, service equipment, and main disconnect, all sized for the calculated load and available fault current.

The maximum fault current, in amperes, that a protective device can safely interrupt without damage or hazard; it must equal or exceed the available fault current at its location.

The maximum current that could flow at a given point in a system during a short circuit, determined by the utility supply and system impedance, and used to select equipment ratings.

An unintended low-resistance connection between energized conductors or between a conductor and ground that causes very high current until a protective device opens the circuit.

A device with two or more coupled windings that changes alternating voltage and current levels by electromagnetic induction, with power roughly conserved apart from losses.

The ratio of primary to secondary winding turns, which sets the ratio of primary to secondary voltage and inversely relates primary and secondary current in an ideal transformer.

The brief, high current drawn when a transformer is energized, caused by core saturation; it can trip instantaneous overcurrent devices and must be considered when coordinating protection.

Selecting protective device settings and ratings so that the device nearest a fault opens first, limiting the outage and preventing upstream devices from tripping unnecessarily.

A generator kept ready to supply a building when the normal utility source fails, connected through transfer equipment that prevents backfeed to the utility and restores power automatically or manually.

A device that switches loads from the normal supply to an alternate source, arranged to prevent both sources from being connected to the load at the same time.

A system with stored energy that supplies power without interruption during a brief outage or until a generator starts, protecting sensitive equipment from dips and dropouts.

An instrument that applies a high direct voltage to insulation and measures resistance, used to check that conductors and windings are not leaking to ground before energizing equipment.

A combination of contactors and overload protection that controls a motor's start and stop and disconnects it if current stays too high, protecting windings from overheating.

A protective device that senses sustained excess current in a motor circuit and opens the control circuit, allowing the motor to cool before it is restarted.

An electronic unit that rectifies incoming power and switches it to produce adjustable voltage and frequency, letting an alternating-current motor run at controlled speeds and save energy.

A complete lighting unit consisting of the lamp or lamps plus the housing, optics, ballast or driver, and provisions for mounting and connecting to the branch circuit.

A component that limits and regulates current through a discharge lamp, and in some types provides the starting voltage needed to strike the arc.

A low-power circuit supplied by a listed source that limits voltage and current, permitting lighter wiring and reduced spacing because the shock and fire risk is low.

Wiring and equipment operating at a voltage low enough to limit shock hazard, commonly used for controls, communications, and signaling, and often subject to rules different from power circuits.

The process of counting and measuring materials from drawings to produce a quantity list, which becomes the basis of a material cost estimate and a purchase order.

A structured list of every component required for an installation, with descriptions, quantities, and often part numbers, used for procurement and for checking delivery against the design.

A drawing revised after construction to show the actual installed routing, sizes, and locations, used for maintenance, future renovations, and verification against the permit set.

The formal authorization from the authority having jurisdiction to perform regulated electrical work, issued after plan review and required before work begins on most installations.

The organization or official responsible for enforcing the electrical code and approving equipment and installations, whose interpretation governs acceptance of the work in that area.

The status of equipment that has been evaluated by a recognized testing organization and found to meet a published safety standard, allowing it to be installed as intended.