QLD Electrical Licence key terms

The fixed relationship in a resistive circuit that voltage equals current multiplied by resistance (V = I x R). Rearranging it lets you find current or resistance and predict how a circuit will behave when values change.

The ratio of true power in watts to apparent power in volt-amperes in an alternating current circuit, expressed from zero to one. A low power factor means larger current is drawn for the same useful output.

The total opposition an alternating current circuit presents to current flow, combining resistance and reactance and measured in ohms. It determines current magnitude and the phase relationship between voltage and current.

The declared standard voltage of a low-voltage supply in Australia: 230 volts between phase and neutral and 400 volts between phases. Cable selection, equipment ratings and voltage drop limits are all referenced to it.

The current that would flow at a given point of an installation if a bolted short circuit occurred there, determined by supply impedance. It is used to choose protective devices with adequate breaking capacity and to check discrimination.

The reduction in voltage along conductors caused by their impedance carrying load current. Installations are generally limited to about five per cent total drop from the point of supply to the furthest point of use.

The maximum current a conductor can carry continuously under stated installation conditions without its insulation exceeding the permitted operating temperature. Tabulated values are adjusted for the actual installation environment.

Multiple Earthed Neutral: the supply neutral is connected to earth at the distribution transformer and again at each consumer's main switchboard. This keeps exposed metalwork near earth potential and gives a low-impedance fault path.

The conductor that connects the main earthing terminal or bar of an installation to the earth electrode. It carries fault current to earth and must be sized and protected against damage and corrosion.

A conductive element, such as a driven rod or copper strip, buried in contact with the general mass of earth. It provides the installation's connection to earth and helps stabilise touch voltages.

Connecting conductive parts that are not intended to carry current, such as water pipes and structural steel, so they sit at substantially the same potential. It reduces the risk of shock from touch voltages during a fault.

The conductor within a circuit that connects exposed conductive parts of equipment to the earthing system. It provides the low-impedance return path that lets a protective device clear an earth fault quickly.

The total impedance of the path taken by fault current from the point of fault through the protective earthing conductor, earth and supply transformer back to the source. It determines whether the protective device will trip within the required time.

The maximum period a protective device may take to automatically clear an earth fault. Typical limits are 0.4 seconds for final subcircuits up to 32 amperes and 5 seconds for distribution circuits.

A circuit breaker or fuse installed to interrupt overload and short-circuit current before conductors or equipment are damaged. Its rating and breaking capacity must suit the circuit and the prospective fault current.

A device that continuously compares active and neutral current and trips when the difference, representing current flowing to earth, exceeds its sensitivity. Thirty milliampere units are used for additional personal protection.

The circuit that runs from its protective device at the switchboard to the points where electricity is used, such as socket outlets and lighting. It is the last level of the distribution system before the load.

The conductors between the point of supply and the main switchboard. They must be sized for the installation's maximum demand, voltage drop and fault level, and are protected by the main switch or a main protective device.

An assembly containing the main switch, protective devices, neutral link and earthing arrangements that distributes supply to subcircuits. It must be accessible, labelled clearly and, in a MEN installation, contain the main earthing terminal.

A test applying a direct voltage, commonly 500 volts, between conductors and between live parts and earth to measure insulation quality. A healthy low-voltage installation should read at least one megohm.

A check confirming that active, neutral and protective earthing conductors are connected to the correct terminals at every point of the circuit. Correct polarity is essential so switches and protective devices control the active conductor.

The combination of visual inspection and testing carried out before an installation or alteration is first energised, confirming it complies with the Wiring Rules. Results must be recorded and compared with the required criteria.

Periodic inspection and electrical testing of plug-in equipment already in use in workplaces, including earth continuity, insulation and polarity checks with a tag showing the next test date. Requirements are set out in AS/NZS 3760.

Queensland's principal electrical safety law, which aims to eliminate or minimise the risk of death, injury and property damage from electricity. It imposes general duties on people conducting businesses and on workers.

A person conducting a business or undertaking. Under Queensland electrical safety law a PCBU owes a primary duty to ensure the electrical safety of workers and others affected by the business so far as reasonably practicable.

A personal licence issued in Queensland by the Electrical Safety Office that authorises the holder to perform electrical work within its scope. Performing electrical work without the appropriate licence is an offence.

The licence a business must hold to carry on the business of performing electrical work in Queensland. It requires a nominated qualified person, adequate insurance and compliance with record-keeping and testing obligations.

Categories of electrical work that Queensland's electrical safety regulation requires to be notified to the regulator and documented. The licensed contractor must complete the required paperwork and give copies to the customer and relevant parties.

The Queensland document completed for notifiable electrical work, recording the work carried out and certifying that it has been tested and is safe. Copies are provided to the customer and, where relevant, the electricity entity.

The practice of proving your tester on a known source, testing the conductors you are about to work on to confirm they are de-energised, then re-proving the tester. It guards against testers that have failed silently.

Disconnecting an installation or circuit from every source of supply and securing that disconnection so it cannot be re-energised while work proceeds. Isolation must be verified by testing before work starts.

The procedure of fitting a personal lock and danger tag to an isolating device so only the person who applied it can restore supply. It prevents accidental re-energisation of equipment being worked on.

A competent person whose sole task is to warn and, if necessary, isolate or rescue while another person works near live parts. The observer performs no other work and stays in a position to see the task.

The minimum distance a person or conductive object may come to exposed live conductors or overhead lines. Queensland's electrical safety regulation sets exclusion zones that vary with voltage and with the person's competence.

The ranked order of control measures: eliminate the hazard, substitute, isolate, engineer, then apply administrative controls and finally personal protective equipment. Higher-ranked controls are more reliable and must be used where reasonably practicable.

The Australian and New Zealand standard setting out safe working practices for low-voltage electrical installations, including isolation, testing for dead and emergency procedures. It underpins safe work methods used by electrical workers.