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?