EWRB Electrical key terms

The relationship stating that current through a conductor is directly proportional to voltage across it and inversely proportional to resistance, expressed as V = I × R.

The total opposition to alternating current flow in a circuit, combining resistance and reactance, measured in ohms and denoted by Z.

The ratio of real power (watts) to apparent power (volt-amperes) in an AC circuit, indicating how effectively electrical power is converted into useful work.

The product of voltage and current in an AC circuit without regard to phase angle, measured in volt-amperes; it combines real and reactive power.

An AC supply using three conductors with voltages displaced by 120 electrical degrees, enabling balanced power delivery and efficient motor operation.

A three-phase connection where one end of each phase winding joins at a common neutral point, giving line voltage equal to √3 times phase voltage.

A three-phase connection where windings form a closed loop, so line voltage equals phase voltage and line current is √3 times phase current.

The reduction in voltage along a conductor caused by current flowing through its resistance and reactance; excessive drop impairs equipment performance and must be limited by design.

The maximum continuous current a conductor can carry under specified installation conditions without exceeding its rated temperature, determined by size, insulation, and installation method.

A multiplier applied to the sum of connected loads to estimate the maximum demand actually drawn, because not all loads operate simultaneously at full rating.

The total impedance of the path taken by fault current from the source through the active conductor, fault, and protective earth back to the source; it determines protective device operation.

The resistance measured between live conductors and earth, or between conductors, using a high-voltage tester; it indicates the integrity of insulation and must meet minimum values.

Electric current that periodically reverses direction, typically varying sinusoidally at a set frequency, and is the standard form of supply for distribution networks.

The number of complete AC cycles per second, measured in hertz (Hz); New Zealand's public supply operates at 50 Hz.

A protective device that disconnects a circuit when it detects a difference between active and neutral currents, indicating current leaking to earth, protecting people from electric shock.

Connecting exposed conductive parts of equipment to earth so that fault current returns safely and protective devices operate, limiting touch voltage during a fault.

The Multiple Earthed Neutral system used in New Zealand, where the neutral is earthed at the supply transformer and at each installation, providing a low-impedance fault path.

Electrical work defined in the Electricity Act and regulations as requiring a licensed or supervised person, covering installation, maintenance, and testing of electrical systems.

Prescribed electrical work classified as higher risk because of voltage, energy, or system complexity; it requires a licensed person and specific certification and inspection.

Prescribed electrical work of lesser risk, such as replacing certain fittings on low-voltage circuits, that still requires competence but has reduced supervision and certification requirements.

An annual licence issued by the EWRB allowing a registered electrical worker to legally carry out or supervise prescribed electrical work in their class.

The combination of knowledge, skills, and experience needed to safely perform prescribed electrical work to the required standard, maintained through ongoing practice and training.

Oversight of electrical work by a licensed person who ensures the work is done safely and competently, with the level of direct or general supervision depending on the worker's licence.

The formal declaration by a licensed electrical worker that completed prescribed electrical work complies with the relevant standards and regulations, supported by required testing and records.

A certificate issued for prescribed electrical work confirming it is safe to connect and complies with requirements; it must be provided to the owner and retained as a record.

A documented record of tests and inspections performed on an installation, including results and dates, kept to verify compliance and support future maintenance and certification.

The joint Australian/New Zealand Wiring Rules standard that specifies requirements for designing, installing, and verifying electrical installations to ensure safety and compliance.

The process of inspecting and testing a completed electrical installation to confirm it meets AS/NZS 3000 and is safe to energise, before handover to the owner.

The periodic inspection and electrical testing of portable appliances and equipment, followed by labelling, to confirm they remain safe for use in the workplace.

The standard that sets out in-service safety inspection and testing requirements for electrical equipment, including test intervals and pass criteria for portable appliances.

The process of disconnecting electrical equipment from all sources of supply and securing it against reconnection so work can proceed safely on de-energised parts.

A safety procedure using locks and warning tags to prevent energy sources from being re-energised while work is being carried out on equipment.

The practice of verifying that a circuit or equipment is de-energised with a proven tester before touching it, confirming isolation has been effective.

The defined safe distance around live electrical equipment that unqualified persons must not enter, and within which only authorised work with appropriate controls may occur.

Electrical work performed on or near energised conductors, permitted only when justified, risk-assessed, and carried out with specialised tools, PPE, and procedures.

Clothing and equipment such as insulating gloves, arc-rated clothing, and safety glasses worn to reduce injury risk from electrical, thermal, and mechanical hazards.

A sudden release of energy caused by an electrical fault between conductors, producing intense heat, light, and pressure that can severely injure workers.

A documented authorisation that defines the scope, hazards, isolation points, and controls for a specific high-risk task, signed before work begins and closed on completion.