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WorksheetsEAL unit 4 revision 4
Total questions: 15
Worksheet time: 8mins
Which device is this about: Its I rating must be equal to or above the normal operating current for the circuit.
the cable
the fuse
the accessory
the distribution board
Which device is this about: Its I rating must be equal to or higher than normal current carrying capacity of the protective device?
the cable
the fuse
the accessory
the distribution board
Calculate the total demand current for a lighting circuit it it contains 20 x 100W GLS lamp units and the diversity factor is 66%
7.8A
8.69
6A
5.7A
When cabling is routed through insulation, its rated current carrying capacity will be:
decreased
increased
stay the same
be doubled be meter embed
if the voltage drop in a final circuit is found to be excessive, the corrective action is to:
limit the time under load
boost the voltage through a transformer
increase the CSA of the supply cable
decrease the CSA of the supply cable
when overload and over current protection is necessary, which of the following is correct?
Ib>In>It
Ib<In>It
Ib<In<It
Ib>In>Iz
Which of the following is correct regarding earth fault loop impedance?
Zs can be obtained by enquiry
Ze can be obtained by enquiry
Zs can be obtained by calculation
Zs can be obtained by measurement
One disadvantage of using the tabulated values of Ze in the OSG is:
they are hard to read
they can be too high
they are unreliable
they can be too low
when checking earth fault loop impedance, which of the following can be used without correction?
BS 7671
GN3
On Site Guide
GS38
The usual correction factors used to calculate the derating factor of a cable are:
thermal insulation, grouping, ambient temp and rewireable fuses
external insulation, grouping, ambient temp and rewireable fuses
cable type, grouping, rewireable fuses and ambient temp
thermal insulation, cable type, ambient temp and grouping
for the PFC, which should be recorded?
the prospective short circuit current
the prospective earth fault current
the highest PFC at the supply
the highest PFC at the furthest point of the circuit
to ensure the effective operation of the OCPD, the earth fault loop path must have:
a 230V supply
a very low resistance
fuses or CB in the live conductor
a high resistance
Shock protection ensures that:
the protective devices operate in a specified time
the actual loop impedance vales are lower than specified
the PFC is low enough to operate the OCPD in time
the circuit is switched off
what % drop is associated with a power circuit?
3%
4%
5%
6%
the design current is referred to as:
Ib
In
It
Iz
