WorksheetsInspection and testing live tests
Total questions: 36
Worksheet time: 18mins
Which of the following is the direct departure from BS7671 when a measured value of Ipf considerably exceeds those permitted for the protective devices installed at the point of test?
Earth fault disconnection times will be exceeded
Devices will safely interrupt the fault in time
Devices will not safely interrupt the fault in time
Disconnection times will be exceeded
What is the maximum permitted disconnection time for 100ma RCD to BSEN 61008 in order to meet specified time/current performance, when tested at 1xI n?
40ms
100ms
200ms
300ms
Which one of the following is used to establish phase sequencing for an installation
Frequency meter
Power factor indicator
Rotating disc instrument
Earth fault loop impedance tester
Which one of the following is the range tests that are carried out for RCD’s
½ x I△n – 150 x I△n
½ x I△n –1 x I△n
½ x I△n – 2 x I△n – 150 x I△n
½ x I△n – 2 x I△n – 5 x I△n
Functional tests are to be carried out on a general purpose RCD using a RCD tester. At which point during the testing process would the effectiveness of the test button on the RCD be checked.
Before the instrument test
Following all instrument tests
Following the 0.5 X I n test but before the 1 x I△n test
At no point as the instrument tests will carry out these functions
The current measured between line and neutral at the origin of an electrical installation forming part of a TT system would be recorded as the
Design current
Nominal Current
Rated current
Prospective fault current
The relationship between the maximum measured (Ipf) and the breaking capacity of any protective device is that the device breaking capacity is
Greater than the measured Ipf
Lower than the measured Ipf
Lower for ring circuits
Lower for radial circuits
Which of the following values is recorded when verifying Ipf for a single phase circuit
The lowest value from PSCC and PEFC
PSCC multiplied by a factor of 2
PSCC added to PEFC
The higher value from PEFC and PSCC
Which of the following is the correct method of measurement for PSCC for a single phase installation using two leads
Using a test instrument on pfc scale between line intake and main earthing terminal
Using a test instrument on pfc scale between neutral intake and main earthing terminal
Using a test instrument on pfc scale between main intake line and neutral
Using a test instrument on ohms scale between main intake line and neutral
Which of the following is the correct method of measurement for PEFC for a single phase installation using two leads
Using a test instrument on pfc scale between line intake and main earthing terminal
Using a test instrument on pfc scale between neutral intake and main earthing terminal
Using a test instrument on pfc scale between main intake line and neutral
Using a test instrument on ohms scale between main intake line and neutral
Which of the following is not a method of determining Ipf
By calculation
By enquiry
By using a RCD tester
By direct measurement using a EFLI tester set to measure Ipf
Which of the following is the correct formula for determining Ipf by calculation
Ipf = Zs/Uo
Ipf = Ze/Uo
Ipf = Uo/Ze
Ipf = Uo/R1+R2
What do the term Ze stand for
Resistance of the line R1 and cpc R2 in ohms
The external earth loop impedance in ohms
Zs the total earth loop impedance in ohms
Insulation resistance in MΩ
Which of the following is the correct method of measurement for Ze for a single phase installation using two leads
Using a test instrument on pfc scale between line intake and main earthing terminal
Using a test instrument on pfc scale between neutral intake and main earthing terminal
Using a test instrument on pfc scale between main intake line and neutral
Using a EFLI tester with the means of earthing disconnected and main switch open between main intake line and disconnected main earthing conductor
Which one of the following supplies would not require phase sequence testing
2 wire TN-C-S
3 wire TN-S
4 wire TT
4 wire TN-C-S
Which one of the following tests would be normally carried out with test connections on the supply side of an installation main switch
External earth fault loop impedance
RCD operation time
Insulation resistance
Voltage drop
Which one of the following combinations of test instruments and units display are used to establish a value of PFC.
PFC tester set to KΩ
PFC tester set to KA
EFLI tester set to MΩ
EFLI tester set to ma
One part of the earth fault loop path for a TN-S system is formed by the
PEN conductor
Neutral conductor
General mass of earth
CPC
Which one of the following devices is suitable for prospective fault currents in excess of 60KA
BS 88
BS 3036
BS 1362
BS EN 60898
A 230v single phase circuit is protected by a 16A type B, BS EN 60898 device. Which one of the following is the minimum value of current that will cause effective disconnection in the required time, if the maximum permitted earth fault loop impedance is 2.73Ω
84A
90A
123A
160A
If the breaking capacity of a BS EN 60898 protective device is given as Icn and Ics which of the following is the definition of Icn rating
The current the device can disconnect but may no longer be serviceable
The current of which the disconnection time will not be achieved
The current the device can disconnect and remain serviceable
The current of which arcing will be eliminated
The type of earthing system which includes a PEN is
TT
TN-S
TN-C-S
IT
The maximum tabulated earth loop impedance value for a protective device is 1.37Ω. The maximum measured value of earth loop impedance permitted for a circuit protected by this is
0.961Ω
1.096Ω
1.370Ω
2.167Ω
Which one of the following is the correct location to connect test leads within an installation in order to test an RCD
As close as possible to the RCD on supply side
At a suitably safe location on supply side of the RCD
As far away as possible from RCD on supply side
At a suitably safe location on the load side of the RCD
The measured value of external fault loop impedance for an installation is 0.4Ω. If the measured R1+R2 value for one of the circuits is 0.5Ω the expected Zs for the circuit is
2.0Ω
0.9Ω
0.8Ω
0.22Ω
The safety precaution to be taken before disconnecting a main protective bonding conductor for testing purpose is to
Warn the occupier of the premises
Isolate the supply and lock off
Check for parallel paths
Use a screwdriver insulated 100v
Insulation resistance between L-E on 230v installation gives a reading of 0.02MΩ. Which one of the following is the approximate value of current that would leak to earth during normal conditions
1.5ma
11.5ma
1.5amps
11.5amps
A test of insulation resistance on a number of circuits produces the following results 10MΩ, 5MΩ, 5MΩ, 4MΩ and 2MΩ
The measured insulation resistance at the distribution board with the circuits connected in parallel will be
26MΩ
10MΩ
5.2MΩ
0.8MΩ
The measured external E.F.L.I. for an installation is 0.2 ohms, if the line and cpc combined is 1.2 the expected earth fault loop impedance for the circuit will be.
0.24 ohms
1.0 ohms
1.4 ohms
3.2 ohms
The external earth loop impedance is 0.6 ohms and the maximum E.F.L.I. from BS7671 for a circuit is 2.19 following any corrections what is the maximum R1+R2 to ensure fault protection.
1.12 ohms
1.31 ohms
1.37 ohms
1.59 ohms
Where no supply is available a test of earth electrode resistance forming part of a TT system will be carried out using.
E.F.L.I. Tester
Continuity tester
Earth Electrode resistance tester
Low resistance ohm meter
Where two copper conductors each with resistance of 0.1 ohms are connected in parallel their combined resistance will be.
0.5 ohms
0.2 ohms
0.1 ohms
0.05 ohms
A check of the RCD should be recommended by pressing the RCD test button.
4 weeks
6 months
16 months
Annually
The maximum test current applied to a 30ma RCD used for additional protection is.
100ma
150ma
30ma
15ma
The maximum test current for 100ma RCD BS EN 61008
50ma
100ma
150ma
500ma
Which one of the following is the maximum permitted disconnection time as given in BS7671 for an RCD installed to provide additional protection when tested at the maximum applied test current?
30ms
40ms
200ms
300ms
