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bobby101
Q21 list three things to check when inspecting overcurrent devices
A21 (i) correct BS and type
(ii) Correct current setting
(iii) adequate breaking capacity
Q22 list four instances where a TN-C-S System is not allowed
A22 (i) construction sites
(ii) supplies to caravans
(iii) supplies to boats etc
(iv) temporary installations
Q23 give the reason that restricts the use of a TN-C-S system on a mobile or transportable unit
A23 A TN-C-S system may only be used if the installation is continuously under the supervision of a skilled or instructed person and the suitability and effectiveness of the earthing system has been confirmed
Q24 list the information you would require for inspection and testing of a new installation
A24 (i) assessment of general characteristics, including
(ii) Maximum demand
(iii) number and type of live conductors
(iv) type of earthing
(v) Supply characteristics, for each source of supply including standby and safety sources. (give details if asked)
Q25 state the type of inspection required on a new installation and what documents require to be filled out by the person conducting the inspection and testing of a new installation
A25 (i) the type of inspection required to be carried out is an initial verification
(ii) The documents that require to filled out are,
(i) Electrical installation certificate
(ii) Schedule of inspections
(iii) Schedule of test results
Q26 list three situations where a warning notice about voltage is required
A26 (i) where the voltage exceeds 230 volts in an enclosure where it would not be expected to exceed 230
Volts
(ii) where the voltage between live parts in different enclosures which are simultaneously accessible exceeds 230 volt
(iii) where there are different nominal voltages present in the same enclosure
Q27 list the method of fault protection most likely to be used for the following
(i) 12 V halogen downlighter
(ii) Shaver socket
(iii) Domestic socket outlet circuit indoors
A27 (i) SELV
(ii) Electrical separation
(iii) Automatic disconnection of supply, protective earthing
Q28 state the maximum voltage in both a.c. and d.c. for SELV systems:-
(i) with bare live parts in normal, dry areas
(ii) in normal, dry areas where basic protection is provided
(iii) in zone 0 of bathrooms or shower rooms
A28 (i) 25 v a.c and 60 v d.c.
(ii) 50 v a.c. and 120 v d.c.
(iii) 12v a.c. and 30 v d.c.
Q29 state why it is necessary to carry out a test of prospective fault current at the main intake position of an installation
A30 a value of prospective fault current needs to be determined at all relevant places. This means where a protective device is situated. The test is made to check that the prospective fault current does not exceed the breaking capacity of the device
Q31 an insulation resistance test is to be carried out on a SELV system. State:-
A. The test voltage to be used
B. The minimum value of insulation resistance allowed by BS 7671
C. The minimum acceptable value of insulation resistance between the SELV circuit and an adjacent low voltage circuit
A31 (i) 250 MΩ
(ii) 0.5 MΩ
(iii) 1.0 MΩ
Q32 state:-
A. Two pieces of legislation applying to the activity of inspection and testing
B. The legal status of the inspector
C. The BS 7671 requirements for the inspector
A32 (i) electricity at work regulations 1989 +health and safety at work act 1974
(ii) the duty holder
(iii) competent
Q33 A. list two methods for checking the continuity of protective conductors
B. state the percentage rise expected in the resistance of a copper conductor between 20⁰C and 70⁰C
A33 A. (i) R1+R2 method
(ii) Long lead method
B. twenty percent
Q34 in the equation Zs=Ze+(R1+R2) State what each of the symbols represents
A34 Zs = Total earth fault loop impedance of the circuit
Ze = external earth fault loop impedance
R1 = the resistance of the line conductor
R2 = the resistance of the circuit protective conductor
Q35 What calculation would you use to determine prospective fault current?
A35 pfc=Uo/Ze Uo = nominal voltage Ze = external earth fault loop impedance
A21 (i) correct BS and type
(ii) Correct current setting
(iii) adequate breaking capacity
Q22 list four instances where a TN-C-S System is not allowed
A22 (i) construction sites
(ii) supplies to caravans
(iii) supplies to boats etc
(iv) temporary installations
Q23 give the reason that restricts the use of a TN-C-S system on a mobile or transportable unit
A23 A TN-C-S system may only be used if the installation is continuously under the supervision of a skilled or instructed person and the suitability and effectiveness of the earthing system has been confirmed
Q24 list the information you would require for inspection and testing of a new installation
A24 (i) assessment of general characteristics, including
(ii) Maximum demand
(iii) number and type of live conductors
(iv) type of earthing
(v) Supply characteristics, for each source of supply including standby and safety sources. (give details if asked)
Q25 state the type of inspection required on a new installation and what documents require to be filled out by the person conducting the inspection and testing of a new installation
A25 (i) the type of inspection required to be carried out is an initial verification
(ii) The documents that require to filled out are,
(i) Electrical installation certificate
(ii) Schedule of inspections
(iii) Schedule of test results
Q26 list three situations where a warning notice about voltage is required
A26 (i) where the voltage exceeds 230 volts in an enclosure where it would not be expected to exceed 230
Volts
(ii) where the voltage between live parts in different enclosures which are simultaneously accessible exceeds 230 volt
(iii) where there are different nominal voltages present in the same enclosure
Q27 list the method of fault protection most likely to be used for the following
(i) 12 V halogen downlighter
(ii) Shaver socket
(iii) Domestic socket outlet circuit indoors
A27 (i) SELV
(ii) Electrical separation
(iii) Automatic disconnection of supply, protective earthing
Q28 state the maximum voltage in both a.c. and d.c. for SELV systems:-
(i) with bare live parts in normal, dry areas
(ii) in normal, dry areas where basic protection is provided
(iii) in zone 0 of bathrooms or shower rooms
A28 (i) 25 v a.c and 60 v d.c.
(ii) 50 v a.c. and 120 v d.c.
(iii) 12v a.c. and 30 v d.c.
Q29 state why it is necessary to carry out a test of prospective fault current at the main intake position of an installation
A30 a value of prospective fault current needs to be determined at all relevant places. This means where a protective device is situated. The test is made to check that the prospective fault current does not exceed the breaking capacity of the device
Q31 an insulation resistance test is to be carried out on a SELV system. State:-
A. The test voltage to be used
B. The minimum value of insulation resistance allowed by BS 7671
C. The minimum acceptable value of insulation resistance between the SELV circuit and an adjacent low voltage circuit
A31 (i) 250 MΩ
(ii) 0.5 MΩ
(iii) 1.0 MΩ
Q32 state:-
A. Two pieces of legislation applying to the activity of inspection and testing
B. The legal status of the inspector
C. The BS 7671 requirements for the inspector
A32 (i) electricity at work regulations 1989 +health and safety at work act 1974
(ii) the duty holder
(iii) competent
Q33 A. list two methods for checking the continuity of protective conductors
B. state the percentage rise expected in the resistance of a copper conductor between 20⁰C and 70⁰C
A33 A. (i) R1+R2 method
(ii) Long lead method
B. twenty percent
Q34 in the equation Zs=Ze+(R1+R2) State what each of the symbols represents
A34 Zs = Total earth fault loop impedance of the circuit
Ze = external earth fault loop impedance
R1 = the resistance of the line conductor
R2 = the resistance of the circuit protective conductor
Q35 What calculation would you use to determine prospective fault current?
A35 pfc=Uo/Ze Uo = nominal voltage Ze = external earth fault loop impedance
