C&G 2391 MOCK Exam One With Answers

11. There are a number of documents that are relevant to the Inspection and Testing of an electrical installation. State
- a) One statutory document (1 mark)
- b) Two none statutory documents (2 marks)

12. State THREE human senses that could be used during the inspection and test of an electrical installation? (3 marks)

13. What is the degree of protection provided by the following enclosures? (3 marks)
- a) IEXXB
- b) IP4X.
- c) IPXS.

14. State THREE functional tests that could be carried out on a domestic installation. (3 marks)

15. From the formula Zs = Ze +   state what is represented by (3 marks)
- a) Ze
- b) R2
- c) 1.2

16. List  in the correct sequence, the FIRST THREE tests that should be carried out during an initial verification on a new office installation. (3 marks)

17. Name THREE different protective conductors that would need to be connected to the main earthing terminal of an installation. (3 marks)

18. Identify the earthing systems that would have the following characteristics (3 marks)
- a) A supply cable in which the functions of earth and neutral are performed by one conductor?
- b) A multi-core supply cable with a separate neutral and earth?
- c) An overhead line supply with no earth?

19. State THREE reasons for conducting a polarity test on an electrical installation? (3 marks)

20. The following readings were obtained during the initial tests on a healthy ring final circuit (3 marks)
L1 to L2 - 0.3 ohm
N1 to N2 - 0.3 ohm
CPC1 to CPC2 - 0.3 ohm

a) What readings would you expect after cross connection?
- i) Between L and N conductors at each socket outlet.
- ii) Between L and CPC at each socket outlet?

b) What does the L to CPC reading represent?

21.
- a) What documentation / information would you need in order to carry out the inspection and verification? (5 marks)
- b) What consideration should be given to the existing installation from which this new installation is fed? (4 marks)
- c) Where should the documentation / information be located? (3 marks)
- d) What notable details regarding this installation should have been included on such documentation? (3 marks)

22. The test results shown in the table below were obtained from the workshop ring final circuit continuity test. (For the first five sockets ONLY)
State whether the readings for each socket are satisfactory or unsatisfactory, giving reasons for those readings deemed to be unsatisfactory (I5 marks)
(Note - Phase, Neutral and CPC loops end to end measurement = 0.8 ohms)

23.
- a) Describe all the steps required to carry out an insulation resistance test on this workshop installation. (8 marks)
- b) The test result indicates an overall value of 1.60 MQ. State, with reasons, what actions, should be taken (if any). (7 marks)

24. The two PIR controlled security lights are each wired on its own radial circuit.
- a) List ALL the component parts of the earth fault loop path associated with one of these circuits in the event of a fault to earth. (8 marks)
- b) If the maximum value of earth fault loop impedance for this circuit is 3.0 ohms and an earth fault causes a current of 200 A to flow. Show by calculation if this value will disconnect the circuit in the required time? (7 marks)

25. State FIVE areas of inspection for this installation that should be carried out prior to testing. (15 marks)

26. An earth fault loop impedance test on the workshop fluorescent lighting circuit has been conducted but no reading can be obtained, as the 6A Type B MCB trips repeatedly. Explain
- a) Why this is the case? (8 marks)
- b) How this problem may be overcome in order to conduct the test? (7 marks)