Answer ALL questions. Look for any feedback given if you get an answer incorrect. Keep choosing an answer until you get it correct. CORRECT or INCORRECT answers are indicated at the TOP of the page. A score is given at the TOP of the page when the exercise has been completed. © K.Brown 2022

- Which Earthing system has an Earth Electrode at the substation transformer and at the consumers premises, and uses the 'general mass of earth' as the main earthing conductor between the two?
- TT system
- TN-S system
- TN-C-S system
- TN-C system

- Which Earthing system has an Earth Electrode at the supply transformer and uses the 'metallic sheathing of a supply cable' as the main earthing conductor between the supply transformer and the consumers premises ?
- TT system
- TN-S system
- TN-C-S system
- TN-C system

- What name is given to the 'combined' Earth and Neutral conductor in a TN-C-S Earthing system?
- LEN
- TEN
- PEN
- SEN

- Which Earthing system has an Earth Electrode at the supply transformer and uses a 'combined Neutral and Earth conductor' as the main earthing conductor between the supply transformer and the consumers premises ?
- TT system
- TN-S system
- TN-C-S system
- TN-C system

- What is the 'average' assumed impedance of a 'TT' system?
- 0.8 ohms
- 0.35 ohms
- 21 ohms
- 10 ohms

- What is the 'average' assumed impedance of a 'TN-S' system?
- 21 ohms
- 0.35 ohms
- 0.8 ohms
- 10 ohms

- What is the 'average' impedance of a 'TN-C-S' system?
- 21 ohms
- 0.8 ohms
- 0.35 ohms
- 10 ohms

- What is the 'average' impedance of a 'TT' system?
- 0.35 ohms
- 0.8 ohms
- 21 ohms
- 10 ohms

- Which Earthing System MUST have a (main) R.C.D as additional protection?
- TT
- TN-S
- TN-C-S
- TN-C

- What is the operating principle of a Residual Current Device (RCD)?
- thermal overload
- current balance
- magnetic overload
- voltage balance

- When calculating 'fault current', which 'ohms law' formula would be used?
- I = V/R
- I = V + R
- I = R/V
- I = R x V

- What name is given to the connection in a transformer where the Earth and Neutral connect together?
- central point
- star point
- earthing point
- EN point

- If three windings in a 3-phase machine are identical to each other, which conductor is not required?
- one of the lives (lines)
- one of the phases
- the earth
- the neutral

- What other name is given for a 3-phase system?
- polyphase
- triphase
- triple-phase
- multi-phase

- Identify the name of the earthing conductor that connects extraneous metallic parts together?
- main earth
- main equipotential bonding
- supplementary bonding
- circuit protective conductor

- Identify the name of the earthing conductor that connects exposed conductive parts to the main earthing terminal (MET)?
- main earth
- main equipotential bonding
- supplementary bonding
- circuit protective conductor

- Identify the name of the earthing conductor that connects service and structural extraneous conductive parts to the main earthing terminal (MET)?
- main earth
- main equipotential bonding
- supplementary bonding
- circuit protective conductor

- Identify the chapter in BS7671 that details protection against electric shock
- chapter 41
- chapter 42
- chapter 43
- chapter 44

- Identify the chapter in BS7671 that details protection against overcurrent
- chapter 41
- chapter 42
- chapter 43
- chapter 44

- State the minimum size for a supplementary bonding conductor that is not protected against mechanical damage?
- 1.5 sqmm
- 2.5 sqmm
- 4.0 sqmm
- 10 sqmm

- State the minimum size for a supplementary bonding conductor that is protected against mechanical damage?
- 1.5 sqmm
- 2.5 sqmm
- 4.0 sqmm
- 10 sqmm

- a TN-S system of earthing has a supply live (line) conductor that is 10 sqmm csa (cross-sectional area). Select the appropriate minimum csa for the protective conductor?
- 10 sqmm
- 6.0 sqmm
- 16 sqmm
- 25 sqmm

- a TN-S system of earthing has a supply live (line) conductor that is 16 sqmm csa (cross-sectional area). Select the appropriate minimum csa for the protective conductor?
- 16 sqmm
- 6.0 sqmm
- 10 sqmm
- 25 sqmm

- a TN-S system of earthing has a supply live (line) conductor that is 25 sqmm csa (cross-sectional area). Select the appropriate minimum csa for the protective conductor?
- 16 sqmm
- 6.0 sqmm
- 10 sqmm
- 25 sqmm

- a TN-S system of earthing has a supply live (line) conductor that is 35 sqmm csa (cross-sectional area). Select the appropriate minimum csa for the protective conductor?
- 16 sqmm
- 6.0 sqmm
- 10 sqmm
- 25 sqmm

- a TN-S system of earthing has a supply live (line) conductor that is 50 sqmm csa (cross-sectional area). Select the appropriate minimum csa for the protective conductor?
- 25 sqmm
- 50 sqmm
- 10 sqmm
- 16 sqmm

- a TN-S system of earthing has a supply live (line) conductor that is 95 sqmm csa (cross-sectional area). Select the appropriate minimum csa for the protective conductor?
- 50 sqmm
- 20 sqmm
- 100 sqmm
- 95 sqmm