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Cork Institute of Technology
Higher Certificate in Engineering in Electrical Engineering – Award
(NFQ Level 6)
Summer 2007
Electrical Planning and Project
(Time: 3 Hours)
Answer FIVE questions.
In marking scripts, the Examiner will take account of clarity of expression and communication skills.
All questions carry equal marks.
Examiners: Mr. J. Buckley Mr. M. Hennessy Prof. E. McQuade
Q1. (a) Define the following terms when used in lighting system design. (i) BZ Classification (ii) Daylight Factor (iii) Efficacy (iv) Standard Maintained Illuminance (v) Light Loss Factor (vi) Utilisation Factor (6 marks)
(b) Two lighting standards are mounted 50 m apart; a single lantern with a uniform light intensity (in all directions) of 5000 candelas is mounted at a height of 10 m on each standard. Calculate the illuminance at a point between the two lighting standards located 9 m from one standard and 41 m from the other. (8 marks)
(c) Suggest some remedies for solving the problem of discomfort glare associated with an artificial lighting installation. (6 marks)
Q2. As consultant electrical engineering technician, your job is to plan the layout of a main distribution and metering system for a new shopping centre. The board incorporates both the ESB metering and the main distribution switchgear for the complex. The complex houses: 3 shops each with a load of 50A, 400V, 3-phase, 50Hz 1 shop with a load of 100A, 400V, 3-phase, 50Hz 1 main tenant with a load of 250A, 400V, 3-phase, 50Hz The board is located within the complex and there is one ESB incoming supply. Each of the shops is individually metered using centralised metering. The distribution board is fed from a 630 kVA transformer with 4.75% impedance. A sub distribution board located in each tenant’s premises is fed from the main distribution board. (a) Draw a line diagram of the main distribution / metering board showing: (i) The current ratings and short circuit ratings for all protection devices (ii) The location of all meters. State whether whole current or current transformer metering (C/T) metering) will be used. (17 marks) (b) Indicate the IP rating of the switchboard. (3 marks)
Q3. (a) IS 3218 and BS 5839 distinguish between automatic fire systems for the protection of property and those installed for the protection of life. Outline the different classifications for each type. (10 marks) (b) State the main function of each of the following fire alarm system components. (i) automatic door closer (ii) battery (iii) end-of-line resistor/diode (10 marks)
Q4. (a) Explain what is meant by the following types of emergency luminaire: (i) non maintained emergency luminaire (ii) maintained emergency luminaire (iii) sustained (combined) emergency luminaire (6 marks) (b) Emergency lighting is provided for use when the general lighting system fails and must be powered from a source other than the source supplying the general lighting.
(ii) State the trip earth fault current for domestic socket circuits. Why is this level necessary? (iii) Describe, with the aid of a sketch, the operation of a RCD. (6 marks) (b) A UPS is required for a computer room which contains twenty computers. Each computer has a consumption of 360 VA at a power factor 0.56 lagging. The supply is 230 V 1Ø 50 Hz. Diversity of machine use is 80%. Calculate the load on the UPS under stated conditions. (7 marks) (c) The computer room in (b) above requires an electrical sub-distribution board. The board will supply power to the lights and the sockets. Draw a line diagram for a typical installation showing the main switch fuse, RCDs (residual current devices) and MCBs (miniature circuit breakers). What factors should be taken into account when deciding on the number of RCDs to be used in a computer application? (7 marks)
Q7. (a) Discuss the advantages / disadvantages of critical path analysis (CPA) as a tool in project management. (10 marks) (b) An extension has been added to a medium sized factory and you must programme the installation of a 240 mm^2 , 4 core PVC insulated steel wire armoured XPLE insulated (PVC SWA XPLE) cable with copper conductors. The cable must be terminated at both ends. Prepare a CPA and bar chart, showing activities associated with the installation of the cable. (10 marks)
