Egypt Engineering Consultant Electrical key terms

The current that flows when a fault of negligible impedance connects two points at different potential. It determines switchgear ratings, cable thermal withstand and protective device breaking capacity.

The value of current that would flow at a point in an installation if a short circuit occurred there, calculated from source impedance and conductor impedance before the protective device operates.

The reduction in voltage along a conductor caused by its impedance carrying load current, usually expressed as a percentage of nominal voltage and limited by code to keep equipment operating correctly.

A numerical analysis that solves bus voltages, branch currents and power flows across a network for defined generation and demand conditions, used to size equipment and check voltage limits.

A normalization method in which voltages, currents, powers and impedances are expressed as fractions of chosen base values, simplifying calculations across transformers of different ratings.

The percentage of rated voltage that must be applied to one winding, with the other short-circuited, to circulate rated current. It governs short-circuit current magnitude and voltage regulation.

The ratio of real power to apparent power in an AC circuit, ranging from 0 to 1. Low power factor increases current for the same useful power and attracts utility penalties.

The addition of capacitors or synchronous machines to supply reactive power locally, raising power factor, reducing line current, lowering losses and releasing transformer capacity.

Distortion of a waveform by integer multiples of the fundamental frequency, quantified as total harmonic distortion. It causes extra heating, neutral overload and capacitor resonance.

The maximum fault current a switching device can safely interrupt at its rated voltage without damage or dangerous emission, expressed in kA rms symmetrical or peak.

The peak current a switching device can withstand and close onto during a fault, including the asymmetric first-cycle peak, without contact welding or mechanical damage.

The selection of protective device ratings and settings so that the device nearest a fault trips first, isolating the smallest possible part of the installation while upstream devices remain closed.

A graph plotting operating time against current for a protective device, showing inverse-time and instantaneous regions. Overlaying curves verifies discrimination between upstream and downstream devices.

A relay whose tripping time decreases as fault current increases, following a defined characteristic curve. Used for backup and feeder protection where definite-time grading is impractical.

A device that trips when the vector sum of currents in live conductors exceeds a set residual value, providing protection against earth leakage, electric shock and fire.

The total impedance of the path taken by fault current from the origin, through the live conductor, the fault, the protective conductor and back to the source, used to verify disconnection times.

Deliberate electrical connection of exposed conductive parts and extraneous conductive parts to bring them to substantially the same potential, preventing dangerous touch voltages during faults.

A conductor or group of conductors buried in contact with the soil to provide an electrical connection to earth, characterized by its resistance to remote earth.

Potential differences appearing on the ground surface near an earthed fault point that can drive current through a person's feet or hand-to-feet path; they govern earthing grid design.

A complete arrangement of air terminations, down conductors and earth terminations designed to intercept lightning strikes and conduct current safely to earth, classified by lightning protection level.

A component that limits transient overvoltages by diverting surge current to earth, coordinated in type and rating across installation levels to protect equipment from lightning and switching surges.

The luminous flux incident per unit area on a surface, measured in lux (lumens per square metre). It is the primary design quantity for task lighting in codes and standards.

The ratio of luminous flux emitted by a lamp to the electrical power it consumes, in lumens per watt. Higher values mean more light for less energy.

The proportion of luminous flux leaving a luminaire that reaches the working plane, accounting for room geometry and surface reflectances in the lumen method of lighting design.

A multiplier applied in lighting design to account for light loss from lamp depreciation and dirt on luminaires and surfaces over time, ensuring maintained illuminance is met.

A lighting fitting using light-emitting diodes with integrated driver and thermal management, characterized by high efficacy, long life and sensitivity of output to junction temperature.

Reduction of a cable's tabulated current-carrying capacity by correction factors for ambient temperature, grouping, soil thermal resistivity, burial depth and protective enclosure.

The conductor that carries return current in a single-phase circuit or the vector sum of phase currents in a three-phase system; it may be overloaded by triplen harmonics.

A prefabricated assembly of copper or aluminium bars in a metal enclosure used for high-current distribution, offering tap-off points and easier installation than multiple cable runs.

A test on a representative sample of a device or assembly to verify it meets a standard's performance requirements, results being valid for all units of that design.

A test performed on every manufactured unit before delivery to confirm workmanship and correct functioning, such as insulation resistance, polarity and functional operation checks.

A structured set of tests witnessed by the purchaser at the manufacturer's works to confirm equipment complies with specification before shipment, reducing site rework and delay.

Testing performed after installation on site to verify equipment is correctly assembled, connected and functioning within specified tolerances before handover to the owner.

The systematic process of energizing, adjusting, testing and documenting installed systems to confirm they operate safely and meet design intent before handover.

A measurement of resistance between live conductors and earth, or between conductors, using a DC test voltage, to detect insulation deterioration, moisture and contamination.

A drawing revised after construction to record the installation as actually built, including routing changes and deviations, forming part of the handover documentation.

A formal instruction issued under a contract to change the scope, quantity or timing of works, with associated valuation and time implications agreed through the contract's change procedure.

A standard form of contract for construction works where the employer designs, widely used in Egypt and the region, defining engineer's role, payment, claims and dispute procedures.

A formal decision by the contract engineer on a matter such as a claim or dispute, made fairly and in accordance with the contract, subject to notice and challenge procedures.

A situation where an engineer's personal, financial or other interest could improperly influence professional judgement, requiring disclosure and where necessary withdrawal from the decision.