NVQ L4 Electrician flashcards

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

Safe isolation procedure

Identify circuit, isolate all live conductors, lock off and tag, prove voltage indicator on known source, test for dead at point of work, then re-prove indicator.

GS38 voltage indicator

Voltage detector to GS38 has fused leads, finger guards, limited exposed probe tips and is proved on a known live source before and after the dead test.

30 mA RCD protection

BS 7671 requires 30 mA additional protection for socket outlets rated up to 32 A and for mobile equipment up to 32 A used outdoors.

Waste duty of care

Anyone producing electrical waste must segregate it, store it securely, transfer it only to authorised carriers and keep waste transfer notes for the required period.

Design current Ib

Ib is the current the circuit is expected to carry in normal service; it must not exceed the protective device rating In or the cable current-carrying capacity Iz.

Voltage drop limits

For public low-voltage supplies BS 7671 gives 3% for lighting and 5% for other circuits from the origin of the installation to the load.

Earth fault loop impedance

Zs is the loop impedance at the far end of a circuit; disconnection is achieved when Zs is low enough for the protective device to operate within the required time.

Adiabatic equation

The protective conductor must satisfy k²S² ≥ I²t, where k depends on conductor material and insulation, S is cross-sectional area, I is fault current and t is disconnection time.

Insulation resistance test

With supply isolated and sensitive equipment disconnected, apply 500 V DC between live conductors and earth; a healthy 230/400 V installation should read at least 1 MΩ.

Ring final continuity test

Measure end-to-end r1, rn and r2, then cross-connect the two legs; socket readings should be broadly equal, and a high reading indicates an open conductor or poor termination.

RCD 5I test

At five times rated residual current a 30 mA RCD should trip within 40 ms; the half-rated current test should not trip it.

EICR purpose

An Electrical Installation Condition Report records the condition of an existing installation, including inspection, test results, classifications C1, C2, C3 and FI, and overall assessment.

Half-split fault finding

Divide the circuit into sections and test at the midpoint; the result shows which half contains the fault, reducing the number of tests needed.

N-E insulation fault

A low insulation resistance between neutral and earth can cause RCD nuisance tripping; disconnect loads and test sections to locate the leakage path.

Broken ring final

A ring with a disconnected leg behaves as two radial circuits; sockets may have high loop impedance, overloaded cables and heat damage at terminals.

Thermal imaging survey

An infrared camera shows temperature differences under load; hot joints, overloaded conductors, unbalanced phases and failing components appear as abnormal hotspots.

Polarization index

For motor insulation, PI is the 10-minute insulation resistance divided by the 1-minute value; a value below about 2 may indicate moisture or contamination.

Condition-based maintenance

Maintenance triggered by measured condition such as temperature, insulation resistance or vibration rather than fixed time intervals, reducing unnecessary intervention and unexpected failure.

CMMS asset register

A computerised maintenance management system stores asset details, maintenance plans, work orders and history so that planned and reactive work can be scheduled and audited.

Partial discharge

Small electrical discharges within insulation that erode materials over time; they can be detected by acoustic, ultrasonic or electrical sensors before failure.

Critical path

The longest sequence of dependent activities through a project network; any delay on it delays completion unless the plan is changed.

Earned value SPI

Schedule performance index equals earned value divided by planned value; below 1 means the project is behind the planned schedule.

Resource levelling

Moving activities within their float to reduce peak resource demand, which may extend the project duration but avoids excessive labour or plant.

Commissioning plan

A document setting out inspection, testing, energisation, performance checks, responsibilities and acceptance criteria for systems before handover to the client.

EAWR 1989

The Electricity at Work Regulations require electrical systems to be constructed and maintained to prevent danger, and work on them by competent persons using safe systems.

Part P notification

In England and Wales, certain electrical work in dwellings is notifiable under Building Regulations Part P and must be certified through a competent person scheme or building control.

CDM notification threshold

A construction project is notifiable to HSE under CDM 2015 if it lasts more than 30 working days with more than 20 workers simultaneously, or exceeds 500 person-days.

NEC early warning

Under NEC contracts the project manager and contractor must give early warning of matters that could increase cost, delay completion or impair performance, and attend risk reduction meetings.

LED efficacy

LED efficacy is light output in lumens divided by electrical power in watts; higher lm/W gives lower energy use for the same illuminance.

PV inverter efficiency

Inverter efficiency is AC energy output divided by DC energy input; European or weighted efficiency better represents part-load operation than peak efficiency.

EV charging RCD

For Mode 3 EV charging BS 7671 requires 30 mA RCD protection; Type A may be used with 6 mA DC detection, otherwise Type B is needed.

Heat pump COP

Coefficient of performance is heat output divided by electrical input at a given condition; seasonal SCOP gives a more realistic annual efficiency.