NVQ L4 Electrician key terms

Documented procedure for proving an installation or circuit dead: identify the supply, isolate, lock off and tag, prove the voltage indicator on a known source, test every conductor, then re-prove the indicator.

Formal written authorisation allowing specified work on or near a hazardous system under stated precautions, issued by an authorised person, with checks before work starts and a handback on completion.

Two linked documents: the risk assessment identifies hazards, who may be harmed and the controls; the method statement describes the safe sequence of work, plant, PPE and emergency arrangements.

Recorded assessment required by the Control of Substances Hazardous to Health Regulations of substances used or produced by the work, covering health effects, exposure routes, controls, monitoring and emergency action.

Waste Electrical and Electronic Equipment Regulations require producers to fund take-back and recycling; electricians must keep waste cable, luminaires and electronics apart from general waste and use authorised carriers.

Allowance that only part of the connected load operates at any one time. Applied to maximum demand using BS 7671 guidance so supply capacity and protective devices are sized realistically, not for every load running together.

Reduction in voltage along conductors caused by their impedance under load. BS 7671 limits it to 3 per cent for lighting and 5 per cent for other uses on public low-voltage supplies so equipment works correctly.

Conductor connecting extraneous-conductive-parts such as metallic water and gas pipes or structural steel to the main earthing terminal, sized against the supply conductors using BS 7671 Table 54.8.

Coordination of protective devices so the device nearest a fault clears it first while upstream devices stay closed, limiting the part of the installation affected by the outage.

Device comparing line and neutral current that trips when imbalance exceeds its rated residual current, giving additional protection at 30 mA and fault protection where loop impedance is too high for overcurrent devices.

Total impedance of the path taken by earth fault current: line conductor, protective conductor, supply earth and any parallel paths. Measured live to confirm disconnection times comply with BS 7671.

Highest current that would flow if a short circuit or earth fault occurred at a point. Measured or calculated to confirm devices can safely break it and equipment withstand ratings are not exceeded.

Dead test applying 500 V DC between live conductors and protective earth to show the insulation is sound; BS 7671 requires at least 1 megohm for the installation, with a lower test voltage for SELV and PELV.

Combined resistance of a circuit's line conductor and protective conductor, measured at points around the circuit; added to the external loop impedance to give Zs and confirm the disconnection path.

Inspection and testing of a new or altered installation before it is energised for use, confirming it matches the design and complies with BS 7671, followed by the appropriate certificate and schedules.

Report on the condition of an existing installation produced after periodic inspection and testing, listing observations coded C1, C2, C3 or FI and giving a date for the next inspection.

Logical fault-finding approach in which a circuit or system is divided into halves and tested to see which section holds the fault, repeating the division until the faulty item is located.

Break in a conductor, terminal or component that stops current flowing. Symptoms include no supply at the point, infinite resistance readings, or equipment that fails when a connection is disturbed.

Unintended connection between a live conductor and earth or an exposed-conductive-part, causing fault current to flow so protective devices operate and touch voltage rises until disconnection.

Fault appearing only under particular conditions such as vibration, heat, moisture or load, which often passes routine tests; locating it needs monitoring, load cycling and checks on connections.

Scheduled maintenance at fixed intervals of time, operating hours or cycles, using manufacturer instructions, regulations and service history to reduce the chance of failure and keep equipment compliant.

Infrared survey of energised equipment that reveals abnormal heat from loose connections, overload or phase imbalance; findings are judged against ambient temperature and similar equipment under comparable load.

Monitoring measurable parameters such as temperature, vibration and insulation resistance, then scheduling maintenance when readings or trends pass defined limits rather than at fixed calendar intervals.

Team-based method listing how each part can fail, the effect on the system, and ratings for severity, likelihood and detection, producing a priority order for maintenance, spares and design improvement.

Horizontal bar chart of activities against a calendar showing start and finish dates, durations, dependencies and progress, used to plan, communicate and track a work programme.

The longest chain of dependent activities in a project network, which sets the shortest possible overall duration; delay to any activity on it delays completion unless the plan changes.

Priced schedule listing measured quantities of work, materials and labour for a project, used to obtain tenders, form the contract sum and value progress payments and variations.

Formal instruction changing the scope, quantity, quality or timing of work from the contract documents; it must be authorised, recorded and valued to keep the account and programme under control.

Percentage held back from interim payments, released in stages at practical completion and after the defects liability period, giving the client money to correct defects if the contractor does not return.

Fixed period, commonly twelve months after practical completion, during which the contractor must return and put right notified defects at their own cost.

Requirement in England and Wales that electrical work in dwellings and associated gardens is designed and installed safely, with certain work notifiable and self-certified by registered competent persons.

Converts direct current from PV modules into grid-synchronised alternating current, tracks the array's maximum power point and must disconnect automatically when the grid supply is lost to prevent islanding.

Rechargeable battery bank with inverter and controls storing electricity for peak shaving, load shifting or backup; installation raises fire, ventilation, earthing and grid-connection issues that must be designed and approved.

Equipment delivering energy to an electric vehicle to BS EN 61851; a mode 3 a.c. charge point uses a dedicated supply and control pilot signal, with specific earthing and RCD requirements for charging.

Ratio of real power in kilowatts to apparent power in kilovolt-amperes. A low value means higher current for the same useful output, increasing losses and charges; corrected with capacitors or active filters.

Changing when a site uses electricity in response to tariffs or grid signals, for example delaying EV charging or discharging a battery at peak times, cutting cost and network strain.