Scope & Definitions

What is the primary scope of BS 7671:2018+A4:2026?

• ADesign of electrical systems only
• BRequirements for safety of persons and property from electrical hazards✓
• CInstallation of renewable energy systems
• DTesting of electrical equipment only

Answer: BS 7671 establishes the requirements for the design, installation, inspection and testing of electrical installations to protect against electrical hazards.

Which of the following is NOT a voltage band defined in BS 7671?

• AExtra low voltage (< 50V AC)
• BLow voltage (50V - 1000V AC)
• CMedium voltage (1kV - 35kV)
• DUltra-high voltage (> 100kV)✓

Answer: BS 7671 defines Extra Low Voltage, Low Voltage, and High Voltage bands. Ultra-high voltage is not a classification in this standard.

In a TN-S earthing system, what does the 'S' represent?

• ASingle phase
• BSeparate protective conductor✓
• CSeries resistance
• DSupply neutral

Answer: TN-S means the neutral and protective earth are provided by separate conductors throughout the installation.

Which earthing system uses a separate earth electrode at the installation?

• ATN-S
• BTN-C-S
• CTT✓
• DIT

Answer: TT (Terre-Terre) systems use a separate earth electrode at the installation, independent of the supply earth.

What is the purpose of a protective conductor in an electrical installation?

• ATo carry the neutral current
• BTo provide a return path for fault current✓
• CTo supply power to equipment
• DTo measure voltage drops

Answer: Protective conductors provide a return path for fault current to protect against electric shock.

In BS 7671, what is defined as an accessible conductive part?

• AAny metal part of an appliance
• BA conductive part that can be touched and is not a live part✓
• CA part buried underground
• DAn insulated conductor

Answer: An accessible conductive part is a conductive part that can be easily touched and is not normally a live part.

Which term describes the protective conductor connecting extraneous conductive parts?

• AMain protective conductor
• BSupplementary bonding conductor
• CEquipotential bonding conductor✓
• DEarth rod

Answer: Supplementary bonding conductors connect extraneous conductive parts to enhance protection against electric shock.

What does the abbreviation EICR stand for?

• AElectrical Installation Certificate Report
• BElectrical Installation Condition Report✓
• CElectrical Inspection Certification Record
• DElectrical Installation Compliance Review

Answer: EICR is the Electrical Installation Condition Report used for periodic inspection of existing installations.

In the context of BS 7671, what is an 'extraneous conductive part'?

• AAn external metal enclosure
• BA conductive part introduced from outside the installation✓
• CA high-voltage conductor
• DAn earthing electrode

Answer: An extraneous conductive part is a conductive part, not part of the electrical installation, that introduces the possibility of electric shock.

What is the voltage threshold between Extra Low Voltage (ELV) and Low Voltage (LV)?

• A30V AC
• B40V AC
• C50V AC✓
• D60V AC

Answer: The boundary between ELV and LV is 50V AC (or 120V DC for ELV/LV separation).

Which earthing system requires an RCD for all circuits?

• ATN-S
• BTN-C-S
• CTT✓
• DNone of the above

Answer: TT systems require RCD protection on all circuits because there is no metallic return path to the supply earth.

In BS 7671, what does 'basic protection' refer to?

• AProtection against electric shock during normal operation✓
• BProtection of cables from mechanical damage
• COvercurrent protection
• DSurge protection

Answer: Basic protection (formerly called 'basic insulation') protects against contact with live parts during normal operation.