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Level 3 Certificate in Electrotechnical Technology Unit 2 Sample questions answers
##
#Unit 2: Installation (Buildings and Structures): inspection, testing and commissioning
Sample questions
Answer guide
1. List three widely used types of:
a. wiring system
b. wiring enclosure
Solution
a. micc cable
PVC/SWA cable
XLPE/SWA cable
PVC twin and earth cable
fire retardant cable (any 3) (3 marks)
b. PVC trunking
steel trunking
PVC conduit
steel conduit
ducting (any 3) (3 marks)
2. When making an area safe to work in
a. list three procedures to be taken before commencing work
b. describe the permit to work procedure
Solution
a. Use barriers and tapes to cordon off the area.
Place warning signs in appropriate positions.
Isolate equipment from the supply. (3 marks)
b. The permit to work is a formal procedure in the form of written authorisation used to control work in potentially hazardous areas. (3 marks)
3. When carrying out large contracts
a. list three parties likely to be concerned
b. state the purpose of a site record
Solution
a. Client
Contractor
Supplier
Consultant
Sub contractor (any 3) (3 marks)
b. Provides a continuous, updated record of all activities on site.
4. Describe the use of the following in monitoring the progress of a contract
a. a bar chart
b. a site diary
c. variation orders.
Solution
a. To display progress of different parts of a contract graphically. (2 marks)
b. A daily record of events on site. (2 marks)
c. Variation orders are requests for extra work or change to a contract and must be given in writing. The issue of variation orders may affect the main contract progress. (2 marks)
5. With reference to the application and use of residual current devices (RCD)
a. list three situations where R.C.D. protection is required
b. state the primary function of an R.C.D.
c. describe the term nuisance tripping.
Solution
a. For sockets installed on TT earthing systems.
For socket outlets likely to supply portable equipment used out of doors.
Where satisfactory values of Zs cannot be achieved. (2 marks)
b. To limit the severity of electric shock. (2 marks)
c. When tripping occurs due to small leakage currents that do not constitute a real fault. (2 marks)
6.
a. Explain briefly the importance of verification of test instruments before performing tests on an electrical installation.
b. State the purpose of each of the following types of test instrument
i) Insulation Resistance tester
ii) Tong tester
iii) PSCC tester
iv) low ohm reading meter
Solution
a. Verification of test instruments ensures that the meter to be used is functioning correctly and test measurements will be accurate. (2 marks)
b. i) To measure insulation resistance between conductors.
ii) To measure current in a conductor without breaking the circuit.
iii) To measure the prospective short circuit/Earth fault current in a circuit.
iv) To check the continuity of ring circuits or continuity of protective conductors or dead polarity.
(4 marks)
7. A 10 kW 230v shower is supplied using PVC/ PVC multicore cable clipped direct
to the surface over a distance of 15m. The circuit is protected by a BSEN 60898
type C circuit breaker. The ambient temperature is 25 deg C.
Determine
Installation method
Design current
Circuit breaker rating
Correction factor
Minimum cable size
Voltage drop
Solution
Method 1 (Table 4A1)
43.5
45A or 50A depending on source material used
1.03 (Table 4C1)
6mm or 10mm (see c above)
4.76v or 2.871v (see c above)
Identify three items to be checked during the initial inspection process for
steel conduit
steel trunking.
Solution
a. Ensure conduit is securely fastened to building fabric, stress is not placed on the conduit, all fittings are tight to provide a good earth path, conduit capacity is not exceeded, no sharp edges, bushes tight, exposed threads painted over etc. (3 marks)
b. Correct bonding at joints using copper bonding strips, circuit segregation provided if necessary, space factor of the trunking not exceeded, covers fixed correctly etc.
(3 marks)
9. When completing additions to a circuit such as an extra socket
a. state the type of certificate to be issued
b. list three items of information that need to be entered on the form
c. state to who the form should be given.
Solution
a. A minor works certificate. (2 marks)
b. Details of the existing installation.
Description of the minor works.
Test results. (3 marks)
c. The person ordering the work. (1 mark)
10. Describe briefly the purpose and types of information which relate to the electrical installation of the following types of drawing
a. site plan
b. block diagram
c. circuit diagram.
Solution
a. A site plan will show the general layout of buildings and structures on a construction site. The types of information which relate to the electrical installation are layout of sub-stations and distribution cables routes. (2 marks)
b. A block diagram shows the relative position of components within an electrical installation without detail. Its purpose is to provide an uncomplicated view of the interconnection of electrical components within an electrical system. (2 marks)
c. A circuit diagram provides details of circuits and control equipment. It is used to show the specific components used within an electrical system. (2 marks)
11.
a. Explain the importance of coordinating electrical installation contracts with
other trades.
b. Describe one example where joiners/carpenters may be held up due to lack of
coordination with electricians working on the same site.
c. Describe one example where plasterers may be held up due to lack of
coordination with electricians working on the same site.
Solution
a. General construction work requires coordination between different trades to ensure that the work proceeds without delays and that minimum disruption is caused by workers from different trades appearing on site at the same time and working in the same area. Also helps ensure safe working environment. (2 marks)
b. Joiners/carpenters may be ready to lay down floorboards where the electrician has not installed cables which are required to run under the floorboards.
(2 marks)
c. Plasterers may be delayed by the electrician who has not completed a first fix of cables, sockets and switches to the wall where the cables are required to be concealed within the plaster. (2 marks)
12.
a. With the aid of a sketch, show how a 230V single phase supply and a 400V 3 phase supply is produced within a sub-station using a transformer with delta connected 11kV primary windings and star connected secondary windings.
b. State two reasons for balancing the loads across a 3 phase 4 wire system.
Solution
a. (4 marks)


b. The loads should be balanced to ensure
i) the neutral current is kept to a minimum
ii) the cable size is kept to a minimum
iii) optimum use is made of transformer capacity
iv) switchgear sizes are kept to a minimum.
any 2, or other suitable alternatives
(2 marks)
#SmartScreen
Level 3 Certificate in Electrotechnical Technology Unit 2 Sample questions 2 answers
#Unit 2: Installation (Buildings and Structures): inspection, testing and commissioning
Sample questions 2
Answer guide
1 (1.5.d, 1.1.e, 1.3.b/c)
a. Identify the statutory regulations which recommend that except for special circumstances, work should not be carried out on live electrical systems.
b. State who issues, and the purpose of, a
Level 3 Certificate in Electrotechnical Technology Unit 2 Sample questions answers
##
#Unit 2: Installation (Buildings and Structures): inspection, testing and commissioning
Sample questions
Answer guide
1. List three widely used types of:
a. wiring system
b. wiring enclosure
Solution
a. micc cable
PVC/SWA cable
XLPE/SWA cable
PVC twin and earth cable
fire retardant cable (any 3) (3 marks)
b. PVC trunking
steel trunking
PVC conduit
steel conduit
ducting (any 3) (3 marks)
2. When making an area safe to work in
a. list three procedures to be taken before commencing work
b. describe the permit to work procedure
Solution
a. Use barriers and tapes to cordon off the area.
Place warning signs in appropriate positions.
Isolate equipment from the supply. (3 marks)
b. The permit to work is a formal procedure in the form of written authorisation used to control work in potentially hazardous areas. (3 marks)
3. When carrying out large contracts
a. list three parties likely to be concerned
b. state the purpose of a site record
Solution
a. Client
Contractor
Supplier
Consultant
Sub contractor (any 3) (3 marks)
b. Provides a continuous, updated record of all activities on site.
4. Describe the use of the following in monitoring the progress of a contract
a. a bar chart
b. a site diary
c. variation orders.
Solution
a. To display progress of different parts of a contract graphically. (2 marks)
b. A daily record of events on site. (2 marks)
c. Variation orders are requests for extra work or change to a contract and must be given in writing. The issue of variation orders may affect the main contract progress. (2 marks)
5. With reference to the application and use of residual current devices (RCD)
a. list three situations where R.C.D. protection is required
b. state the primary function of an R.C.D.
c. describe the term nuisance tripping.
Solution
a. For sockets installed on TT earthing systems.
For socket outlets likely to supply portable equipment used out of doors.
Where satisfactory values of Zs cannot be achieved. (2 marks)
b. To limit the severity of electric shock. (2 marks)
c. When tripping occurs due to small leakage currents that do not constitute a real fault. (2 marks)
6.
a. Explain briefly the importance of verification of test instruments before performing tests on an electrical installation.
b. State the purpose of each of the following types of test instrument
i) Insulation Resistance tester
ii) Tong tester
iii) PSCC tester
iv) low ohm reading meter
Solution
a. Verification of test instruments ensures that the meter to be used is functioning correctly and test measurements will be accurate. (2 marks)
b. i) To measure insulation resistance between conductors.
ii) To measure current in a conductor without breaking the circuit.
iii) To measure the prospective short circuit/Earth fault current in a circuit.
iv) To check the continuity of ring circuits or continuity of protective conductors or dead polarity.
(4 marks)
7. A 10 kW 230v shower is supplied using PVC/ PVC multicore cable clipped direct
to the surface over a distance of 15m. The circuit is protected by a BSEN 60898
type C circuit breaker. The ambient temperature is 25 deg C.
Determine
Installation method
Design current
Circuit breaker rating
Correction factor
Minimum cable size
Voltage drop
Solution
Method 1 (Table 4A1)
43.5
45A or 50A depending on source material used
1.03 (Table 4C1)
6mm or 10mm (see c above)
4.76v or 2.871v (see c above)
Identify three items to be checked during the initial inspection process for
steel conduit
steel trunking.
Solution
a. Ensure conduit is securely fastened to building fabric, stress is not placed on the conduit, all fittings are tight to provide a good earth path, conduit capacity is not exceeded, no sharp edges, bushes tight, exposed threads painted over etc. (3 marks)
b. Correct bonding at joints using copper bonding strips, circuit segregation provided if necessary, space factor of the trunking not exceeded, covers fixed correctly etc.
(3 marks)
9. When completing additions to a circuit such as an extra socket
a. state the type of certificate to be issued
b. list three items of information that need to be entered on the form
c. state to who the form should be given.
Solution
a. A minor works certificate. (2 marks)
b. Details of the existing installation.
Description of the minor works.
Test results. (3 marks)
c. The person ordering the work. (1 mark)
10. Describe briefly the purpose and types of information which relate to the electrical installation of the following types of drawing
a. site plan
b. block diagram
c. circuit diagram.
Solution
a. A site plan will show the general layout of buildings and structures on a construction site. The types of information which relate to the electrical installation are layout of sub-stations and distribution cables routes. (2 marks)
b. A block diagram shows the relative position of components within an electrical installation without detail. Its purpose is to provide an uncomplicated view of the interconnection of electrical components within an electrical system. (2 marks)
c. A circuit diagram provides details of circuits and control equipment. It is used to show the specific components used within an electrical system. (2 marks)
11.
a. Explain the importance of coordinating electrical installation contracts with
other trades.
b. Describe one example where joiners/carpenters may be held up due to lack of
coordination with electricians working on the same site.
c. Describe one example where plasterers may be held up due to lack of
coordination with electricians working on the same site.
Solution
a. General construction work requires coordination between different trades to ensure that the work proceeds without delays and that minimum disruption is caused by workers from different trades appearing on site at the same time and working in the same area. Also helps ensure safe working environment. (2 marks)
b. Joiners/carpenters may be ready to lay down floorboards where the electrician has not installed cables which are required to run under the floorboards.
(2 marks)
c. Plasterers may be delayed by the electrician who has not completed a first fix of cables, sockets and switches to the wall where the cables are required to be concealed within the plaster. (2 marks)
12.
a. With the aid of a sketch, show how a 230V single phase supply and a 400V 3 phase supply is produced within a sub-station using a transformer with delta connected 11kV primary windings and star connected secondary windings.
b. State two reasons for balancing the loads across a 3 phase 4 wire system.
Solution
a. (4 marks)


b. The loads should be balanced to ensure
i) the neutral current is kept to a minimum
ii) the cable size is kept to a minimum
iii) optimum use is made of transformer capacity
iv) switchgear sizes are kept to a minimum.
any 2, or other suitable alternatives
(2 marks)
#SmartScreen
Level 3 Certificate in Electrotechnical Technology Unit 2 Sample questions 2 answers
#Unit 2: Installation (Buildings and Structures): inspection, testing and commissioning
Sample questions 2
Answer guide
1 (1.5.d, 1.1.e, 1.3.b/c)
a. Identify the statutory regulations which recommend that except for special circumstances, work should not be carried out on live electrical systems.
b. State who issues, and the purpose of, a
