NSW Electrical Licence flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ohm's law

The relationship V = I × R, where voltage in volts equals current in amperes multiplied by resistance in ohms, used to calculate any one value when the other two are known.

Three-phase power formula

For a balanced three-phase load, total power P = √3 × line voltage × line current × power factor, with voltage in volts and current in amperes giving watts.

RMS value

The effective value of an alternating quantity, equal to the peak value divided by the square root of two, which is about 0.707 times the peak value.

Power factor

The ratio of true power in watts to apparent power in volt-amperes; a value below one indicates reactive load, commonly from inductive equipment such as motors.

Conductor resistance formula

Resistance equals resistivity multiplied by length divided by cross-sectional area, so longer or thinner conductors have higher resistance than short or thick ones.

Voltage drop limit

A common design limit of five percent of nominal supply voltage from the point of supply to the furthest point of a final subcircuit, covering mains and subcircuits combined.

TPS conductor colours

In flat thermoplastic sheath cable, brown is the active, blue is the neutral and green with yellow stripes is the protective earthing conductor.

Cable derating factors

Current-carrying capacity is reduced for high ambient temperature, grouping with other circuits, enclosure in thermal insulation and the installation method used.

Sheath colour meaning

White sheath identifies flat thermoplastic sheath cable, while orange sheath identifies circular thermoplastic sheath cable used for mains and submains.

Cable support requirement

Cables must be secured at intervals and within the distance from accessories specified by the manufacturer and the Wiring Rules, and protected where mechanical damage is likely.

MEN system

Multiple earthed neutral system where the supply neutral is earthed at the point of supply and the protective earth bar is linked to the neutral bar at the main switchboard.

Earth fault loop impedance

The total impedance of the path from the supply transformer through the active conductor, the fault and the protective earth back to the source, which limits fault current.

Maximum disconnection time

The time within which a protective device must automatically disconnect a fault; commonly 0.4 seconds for final subcircuits up to 63 amperes.

RCD rated residual current

The residual current at which a residual current device is designed to operate; 30 milliamperes is the value used for additional personal protection.

Equipotential bonding

Connection of metallic services such as water and gas pipes and structural metalwork to the main earthing terminal so that touch voltages between them stay low.

Ingress protection rating

A two-digit code where the first digit rates protection against solid objects and the second rates protection against water, such as IP44 for outdoor equipment.

Class I equipment

Equipment protected by basic insulation and a protective earthing conductor connected to accessible metal parts, relying on the earth to clear an insulation fault.

Class II equipment

Equipment with double or reinforced insulation and no protective earth connection, marked with the double-square symbol and used where earthing is not available.

Switchboard requirements

A switchboard must contain a main switch, protective devices, a main earth bar and neutral bar, plus a legible diagram or schedule of circuits.

Motor circuit protection

Motor circuits need short-circuit protection, overload protection matched to the motor rating, and means of isolation, with emergency stopping where the installation requires it.

Insulation resistance test

A test at 500 volts direct current between conductors and earth, with sensitive equipment disconnected, requiring a result of at least one megohm for the installation.

Verification test sequence

Visual inspection first, then protective earthing continuity, insulation resistance, polarity, earth fault loop impedance and finally residual current device operation testing.

Polarity test

A check that active and neutral are not reversed at outlets and that all switches and protective devices are connected in the active conductor only.

RCD trip time test

A test confirming the device trips within 300 milliseconds at rated residual current and does not trip when tested at half its rated residual current.

Proving a voltage indicator

Checking the voltage indicator on a known live source before and after testing the circuit, so a faulty indicator cannot give a false dead reading.

Hierarchy of control

The order of risk controls from most to least effective: eliminate the hazard, substitute, use engineering controls, then administrative controls, with protective equipment last.

Lock out tag out

Isolation procedure where the supply is switched off, locked and tagged by the worker, and the circuit is proved dead before work begins.

Safety observer role

A person stationed to watch the worker performing live work, able to warn of danger and isolate or rescue, without performing other tasks at the same time.

Notifiable incident

A serious electrical incident or dangerous occurrence that must be reported to the work health and safety regulator, in addition to internal reporting and recording.

Certificate of Compliance

A prescribed document issued for electrical work certifying it complies with the Wiring Rules and safety requirements, with a copy given to the person who commissioned the work.

Licensed electrician requirement

Electrical work in New South Wales must be done by, or under the supervision of, an individual holding the appropriate electrical licence for that class of work.

Wiring Rules standard

AS/NZS 3000 sets the requirements for electrical installations, covering selection, installation and verification of wiring systems and equipment.