UNIVERSITY OF NAIROBI FACULTY OF ENGINEERING DEPARTMENT OF ELECTRICAL AND INFORMATION ENGINEERING

Transcription

1 UNIVERSITY OF NAIROBI FACULTY OF ENGINEERING DEPARTMENT OF ELECTRICAL AND INFORMATION ENGINEERING BUILDING ELECTRICAL SERVICES DESIGN FOR THE BANK OF FAHARI CITY PROJECT INDEX: PRJ 099 BY ODHIAMBO GIFT JUNE F17/1784/2006 SUPERVISOR: DR N O ABUNGU EXAMINER: MR OGABA PROJECT REPORT SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE OF BACHELOR OF SCIENCE IN ELECTRICAL AND ELECTRONIC ENGINEERING OF THE UNIVERSITY OF NAIROBI 2010 SUBMITTED ON: 18TH MAY 2011 i

2 DEDICATION To my late parents who inspired me to follow my dreams ii

3 ACKNOWLEDGEMENTS First and foremost, I would like acknowledge my project supervisor Dr Abungu for his overwhelming guidance, support and encouragement throughout the period this project was carried out I extend special thanks to him for his insightful comments, the guided discovery and feedback in this project Thank you for being my role model and mentor Next, I would like to thank Ronald Onyango for his unfailing commitment, encouragement, patience and support over the years to ensure that I was able to accomplish this project and my studies in spite of the challenges I also acknowledge my colleagues and friends Donna, Evelyn and Victor who challenged me with their input, constructive criticism and patiently extended their help for accomplishing this undertaking I would also like to express my heart-felt gratitude to the Department of Electrical and Electronics Engineering for providing a challenging and enlightening experiencefinally, I offer my gratitude to God for good health, knowledge, wisdom and understanding iii

4 DECLARATION AND CERTIFICATION This BSc work is my original work and has not been presented for a degree award in this or any other university ODHIAMBO GIFT JUNE F17/1784/2006 This report has been submitted to the Department of Electrical and Information Engineering, University of Nairobi with my approval as supervisor: DR NICODEMUS ABUNGU ODERO Date: FICATION iv

5 TABLE OF CONTENTS DEDICATION ii ACKNOWLEDGEMENTS iii DECLARATION AND CERTIFICATION iv TABLE OF CONTENTS v LIST OF FIGURES ix LIST OF TABLES x CHAPTER 1 1 INTRODUCTION 1 LITERATURE REVIEW 2 11 LIGHTING ARTIFICIAL LIGHTING REASONS FOR LIGHTING SOURCES TERMS AND UNITS IN ARTIFICIAL LIGHTING DESIGN LUMINAIRES INTERIOR LIGHTING SCHEME EXTERIOR LIGHTING SCHEME METHODS OF CALCULATING THE NUMBER OF LUMINAIRES 4 12 LIGHTING CIRCUITS ONE-WAY SWITCH6 122 TWO-WAY SWITCH 6 13 POWER POINT LAYOUT 7 v

6 131 RING CIRCUIT LAYOUT RADIAL CIRCUIT LAYOUT 7 14 EARTHING 8 15 ELECTRICAL SERVICE NETWORK DIVERSITY CONSUMER UNITS DISTRIBUTION BOARDS SELECTION OF CABLES DISTRIBUTION SYSTEMS EMERGENCY AND STANDBY POWER SYSTEMS PROTECTION SYSTEMS DISCRIMINATION POWER FACTOR CORRECTION LIGHTNING PHENOMENON 13 CHAPTER 2 16 LIGHTING FITTINGS DESIGN AND POWER POINTS DESIGN INTRODUCTION INTERIOR LIGHTING CALCULATIONS FOR THE BANK LUMEN METHOD OF LIGHTING DESIGN POWER SOCKET DESIGN 18 CHAPTER 3 20 ELECTRIC SERVICES DISTRIBUTION LOAD BALANCING COMPLETE CONSUMER UNIT SPECIFICATION CONSUMER UNIT DESIGN SIZING OF CU CABLES DISTRIBUTION BOARD SPECIFICATION 31 vi

7 341 SIZING OF THE CABLE FEEDING DISTRIBUTION BOARD A DISTRIBUTION BOARD DESIGN OF THREE PHASE LOADS LIFT POWER SUPPLY DESIGN HOSE REEL PUMP POWER SUPPLY DESIGN SIZING OF CABLE FEEDING DISTRIBUTION BOARD B (THE THREE PHASE LOADS) ELECTRICAL DISTRIBUTION SYSTEM RETICULATION BACKUP GENERATOR BACKUP GENERATOR SIZE SIZING OF CABLE FEEDING THE STANDBY GENERATOR POWER FACTOR CORRECTION 40 CHAPTER 4 42 PROTECTION SYSTEMS FAULT CURRENT LEVEL AT THE SWITCHBOARD FAULT CURRENT LEVELS AT THE BEGINNING OF FINAL CIRCUITS DISCRIMINATION BETWEEN CUS AND DBS DISCRIMINATION BETWEEN DBS AND THE SWITCH BOARD DISCRIMINATION BETWEEN AIR CIRCUIT BREAKER (ACB) AND SWITCHBOARD DISCRIMINATION BETWEEN GENERATOR (MOULDED CASE CIRCUIT BREAKER) MCCB AND SWITCHBOARD 49 CHAPTER 5 50 LIGHTNING PROTECTION 50 CHAPTER CONCLUSION RECOMMENDATIONS FOR FUTURE WORK 52 APPENDICES i APPENDIX A i vii

8 APPENDIX B i APPENDIX C i APPENDIX D iii APPENDIX E iv APPENDIX F xviii APPENDIX G xx APPENDIX Hxxii APPENDIX I xxiii REFERENCES xxiv viii

9 LIST OF FIGURES FIGURE 11 POLAR DIAGRAMS 5 FIGURE 12 SWITCHING IN ONE WAY 6 FIGURE 13 SWITCHING IN TWO- WAY 6 FIGURE 14 EXAMPLE OF A RING CIRCUIT CONFIGURATION 7 FIGURE 15 EXAMPLE OF A RADIAL CIRCUIT CONFIGURATION 8 FIGURE 16 EIGHT WAY CONSUMER AND TYPICAL CONTENTS OF A CONSUMER UNIT 9 FIGURE 17 DISTRIBUTION BOARD 10 FIGURE 18 A POWER FACTOR TRIANGLE13 FIGURE 19 PROTECTION ZONES FOR BUILDINGS <20M HEIGHT 15 FIGURE 110 PROTECTION ZONES FOR BUILDINGS >20M HEIGHT 15 FIGURE 21: LIGHT FITTING DESIGN FOR THE BOOK ROOM17 FIGURE 22: POWER POINTS DESIGN FOR THE BOOK ROOM 19 FIGURE 31 DISTRIBUTION BOARD A 33 FIGURE 32 DISTRIBUTION BOARD B 34 FIGURE 33 ELECTRICAL DISTRIBUTION SYSTEM RETICULATION 37 FIGURE 41 SWITCHBOARD SHOWING DISCRIMINATION 47 FIGURE 51 LIGHTNING PROTECTION 50 ix

10 LIST OF TABLES TABLE 21: LIGHTING DESIGN FOR THE GROUND FLOOR 18 TABLE 31: THE TOTAL LOAD WITH DIVERSITY ON THE MEZZANINE FLOOR-RED PHASE 21 TABLE 32: THE TOTAL LOAD WITH DIVERSITY ON THE MEZZANINE FLOOR-YELLOW PHASE 22 TABLE 33: THE TOTAL LOAD WITH DIVERSITY ON THE MEZZANINE FLOOR-BLUE PHASE 23 TABLE 34: THE SUMMARY OF THE TOTAL LOADS OF ALL THE FLOORS OF PER PHASE 24 TABLE 35: CONSUMER UNIT SPECIFICATION 24 TABLE 36: THE ASSIGNMENT OF FITTINGS ON CU GFR1 WAY 1 25 TABLE 37: THE ASSIGNMENT OF FITTINGS ON CU GFR1 WAY 4 26 TABLE 38: THE ASSIGNMENT OF FITTINGS ON CU GFR1 WAY 6 27 TABLE 39:DESIGN SPECIFICATIONS FOR THE FIRST CU ON THE RED PHASE OF GROUND FLOOR 28 TABLE 310: TOTAL LOAD FOR THE FIRST CONSUMER UNIT ON THE RED PHASE OF THE GROUND FLOOR (CUGFR1) 30 TABLE 311 TOTAL LOADS OF THE THREE PHASE ISOLATORS 34 TABLE 312: TOTAL LOAD OF THE ENTIRE BUILDING AND THE THREE PHASE ISOLATORS 38 TABLE 313: TOTAL LOAD OF THE ENTIRE BUILDING AND THE THREE PHASE ISOLATORS 40 TABLE 41 DISCRIMINATION BETWEEN THE CUS AND THE DB A ON THE GROUND FLOOR 45 TABLE 42 DISCRIMINATION BETWEEN THE SWITCHBOARD AND THE DISTRIBUTION BOARDS 46 TABLE 43 CURRENTS ON THE MAINTAINED AND ESSENTIAL BUSBARS PER PHASE 48 TABLE 44 TOTAL GENERATOR PHASE CURRENTS 49 x

11 LIST OF ABBREVIATIONS KV: Kilovolts A: Amperes IEE: Institute of Electrical Engineers KVAR: Kilovolt-amperes reactive KVA: Kilovolt amperes KW: Kilowatts BS: British Standard MCB: Miniature circuit breaker MCCB: Moulded case circuit breaker SC: Single core SP/N: Single phase neutral TP/N: Three phase neutral MI: Mineral Insulated IES: Illuminating Engineering Society W: Watts KPLC: Kenya Power and Lighting Company pu: Per unit Ω: Unit of measurement of resistance Z: Impedance X: Reactance mm: Millimetre m: Meter xi

12 ABSTRACT The main objective of the project was to design the electrical services of the bank of Fahari City The bank consisted of three floors:-the mezzanine floor, ground floor and the first floor area The lighting design was done using lumen method to achieve maximum visual performance and the type of light fittings used mostly were the recessed modular cinqueline with mirror brite louvres This took into account the size and use of the room being lit The power points were placed according to the IEE regulations for a room area of 100 square metres The total load for the building was 4834 KVA Load balancing was attempted with Amps on the Red Phase, 3445 Amps on the Yellow Phase and Amps on the Blue Phase The building had a total number of 15 consumer units with 7 consumer units on the ground floor, 3 consumer units on the mezzanine floor and 5 consumer units on the first floor The building also had 2 distribution boards both located on the ground floor rated at 200A and 630A The cable size between the DB A and the switchboard was 300mm 2 while that between DB B and the switch board was 95mm 2 The voltage drops of the cables were calculated using the MCCB ratings The power systems design had a silent generator rated 500KVA housed in the generator room The generator was SDMO model T1400 with a 1403KVA@ 50Hz The switchboard had a split busbar, that is the maintained busbar and the essential busbar The essential busbar had a maximum current rating of 4593A on the yellow phase Discrimination between the devices was undertaken to ensure coordinated operation The MCBs used for discrimination were rated 32A 100A MCCBs were used for discrimination between CUs and the DBs while a 200A MCCB was used for discrimination between DBs and the switchboard Power correction was done using power factor correction bank rated at 200 KVAR and electronically switched in steps of 25, 25, 50, 50, 50 KVAR Finally lightning protection was done using 16 air terminals which were mounted at the highest point of the roof linked by 25mm by 3mm braided copper strips Earth rods were sunk into the ground at the foot of the building xii

13 CHAPTER 1 INTRODUCTION The objective of this project was to achieve lighting and power distribution for the bank of Fahari City under the IEE (Institution of Electrical Engineers) Standards and Regulations The bank consisted of three floors:-the mezzanine floor, ground floor and the first floor area The design of the lighting scheme was done using lumen method to achieve maximum visual performance The distribution system design, lightning protection and finally protection system design were also undertaken Backup generation was also input to ensure the system maintained a continuous supply in case of failure of the main source (main grid) - Kenya Power and Lighting Co & Ltd supply Therefore, the backup generator size was determined in the project The project focused on the electrical building design The installation part of the electrical services was not dealt with in the project The design had to meet a set of criteria which included: Efficiency: Where a designer had to ensure that maximum output was achieved with minimum input This ensured maximum utilization was achieved with minimal losses; Reliability: The design engineer had to ensure that the design did not have any assumptions or errors that would compromise the consistency of supply Safety: The engineer had to ensure that safety was the number one priority and design ensured that no consumer would be at risk on completion of the project Economy: The design engineer was to ensure that the standards of the project were within a laid down budget and met the present economic needs 1

14 LITERATURE REVIEW 11 LIGHTING 111 ARTIFICIAL LIGHTING Lighting is the application of light, what we do with lights, where they are placed, how much area is lit, what colour white light is chosen, what shadows are cast, or which artwork is accent-the effects it creates [1] 112 REASONS FOR LIGHTING Lighting is essential for security Outdoor security lights are essential components to minimizing the risk of criminal invasion, burglary, or violent attack All sporting events require good light to enable the sport to be played properly and to provide enjoyment for participants and spectators whether present in the venue or watching at home Lighting creates biological effects by supporting people s biological rhythm 113 SOURCES Incandescent lamps are filament lamps where the tungsten iodine lamp is used for floodlighting The gas-filled, general-purpose filament lamp has a fine tungsten wire sealed within a glass bulb The wire is heated to incandescence (white heat) by the passage of an electric current Fluorescent tube is a low pressure variation of the mercury discharge lamp Its energised mercury atoms emit ultra-violet radiation and a blue light The tube is coated internally with a fluorescent powder which absorbs the ultra-violet light and re-radiates it as visible light 114 TERMS AND UNITS IN ARTIFICIAL LIGHTING DESIGN Luminous flux describes the quantity of light emitted by a light source and is expressed in lumen Luminous efficacy describes the luminous flux of a lamp in relation to its power consumption and is therefore expressed in lumen per watt Luminous intensity describes the light output of a source in a given direction It is usually the same in all directions and expressed in candela Illuminance measures the concentration of light falling on a given area It indicates the amount of luminous flux from a light source falling on the given area 2

15 Luminance describes the brightness of an illuminated or luminous surface and is defined as the ratio of luminous intensity of a surface to the projected area of the same surface Its units are in candela per square metre 115 LUMINAIRES There are various types of luminaires One main group comprises decorative luminaires The most common types of luminaires are those with clearly defined photometric qualities [4] Luminaires provide support, protection, and electrical connection to the lamp as well as control of light output Luminaires are usually classified according to the degree of protection against electric shock, the material of the supporting surface for which the luminaire is designed and the degree of protection afforded against ingress of dust and moisture 116 INTERIOR LIGHTING SCHEME The interior lighting scheme requires the consideration of several factors and once met they can be expressed as a series of lighting criteria to facilitate a quality lighting design The standards and Regulations to be complied with include the energy efficiency of the lighting, the effects of the Building Regulations on the design and the requirement of emergency lighting When these objectives have been met they can be expressed as a series of lighting criteria facilitate a quality lighting design [3] The criteria normally considered are level of illumination, uniformity & ratios of illuminance, glare, colour, room reflectance and energy efficiency The areas in a bank where the interior lighting scheme is applied include the Foyer, Lift Lobbies and the Staircase 117 EXTERIOR LIGHTING SCHEME Exterior lighting is important for aesthetic purposes and also to accentuate the features of the landscape All outdoor lighting fixtures must always be aimed, located and maintained to prevent disability glare, which causes reduced visibility and visual performance [5] The light source for the exterior lighting should be either high pressure sodium or metal halide Specific light level criteria should be selected to suit each particular situation [7] The areas in a bank where the exterior lighting scheme is applied include outdoor ATM, security lighting and signage 3

16 118 METHODS OF CALCULATING THE NUMBER OF LUMINAIRES 1181 LUMEN METHOD This method is most suitable for interior lighting design It is normally used to calculate the average illuminance on working planes or to calculate the number of luminaires required to provide a specified average illuminance in rooms It applies only to regular arrays of luminaires The utilization factor (UF) gives the relationship between the light received and light put in This applies only when installation is perfectly clean Installed flux is given by: Installed flux Maintenance factor (MF): It is the ratio that takes into account of how the lighting conditions will deteriorate through use, some due to an average expectation of dirtiness of light fittings and surfaces or due to aging of light fittings [2] Room index (K): Describes the influence of the room geometry in lighting design and is used to determine the utilization factor, It is given by: K H m - Mounting height of the luminaires above working plane ( ) L- Length of the room W - Width of the room The number of light fittings of a particular type and rating can be obtained from their lumen output Where: LDL output-lighting Design Lumens output 4

17 1182 POINT-TO-POINT METHOD This method of calculation is best suitable for outdoor schemes with a small number of light sources It is also used when it is necessary to calculate the illuminance at a small number of points and for indoor schemes where the light reflected onto the working plane from walls and ceilings is negligible The point to point method uses the inverse square law and cosine law for calculation Computer programmes have to be extended to schemes with a large number of sources where the illuminance must be calculated at a large number of points [3] Polar Diagrams Figure 11 illustrates the distribution of luminous intensity, in cd/1000 lm for the transverse (solid line) and axial (dashed line) planes of the luminaire The curve provides a visual guide to the type of distribution expected in addition to intensity It involves use of photometric data Polar diagrams allow a lighting designer to select suitable luminaires and spacing distances based on an acceptable illuminance variation along the working plane [3] Figure 11 Polar diagrams 12 LIGHTING CIRCUITS Lighting circuits are normally protected by a 5A fuse or circuit breaker It is usually advisable to use 15mm 2 twin core and earth so as to carry more current and so that the lighting circuit can be 5

18 enlarged safely by increasing the capacity of the fuse or circuit breaker [10] Lighting circuits can incorporate various switching types: 121 ONE-WAY SWITCH The single-pole switch must be connected to the live conductor to ensure that both live and neutral conductors are isolated from the supply system forms provided that 4% voltage drop of the supply is not exceeded Figure 12 Switching in one way 122 TWO-WAY SWITCH In two-way switching, a single-pole changeover switch is interconnected in pairs Two switches provide control of one or more lamps from two positions Large buildings should have access points and have their own lighting control switch which can be incorporated into a two-way switch circuit The additional controls in two-way switching are referred to as intermediate Figure 13 Switching in two- way 6

19 13 POWER POINT LAYOUT This falls under the category of electrical power circuits in buildings connected in a safe and balanced manner for continuity of supply and consumer satisfaction The power point layout can be divided into two Namely: 131 RING CIRCUIT LAYOUT A ring circuit is used for single-phase power supply to three-pin sockets and it may serve an unlimited number of sockets up to a maximum floor area of 100 square metres [11]Each ring circuit is protected by a 32 amp fuse or trip fitted in the consumer unit Modern installations incorporate a Residual Current Device (RCD) before the consumer unit which trips the whole system if a fault is detected The figure 14 represents a radial circuit Figure 14 Example of a ring circuit configuration 132 RADIAL CIRCUIT LAYOUT A radial circuit may be used as an alternative to a ring circuit to supply any number of power sockets [12] It is a length of appropriately rated cable feeding one power point then proceeding to the next and the circuit terminates with the last power point on it It does not return to the consumer unit or fuse box as seen from the ring circuit Radial circuits are generally used in larger buildings where returning the cable back to the consumer unit can effectively double the cost of installation [14] The figure 15 represents a radial circuit 7

20 Figure 15 Example of a radial circuit configuration 14 EARTHING Earthing connects all these parts which could become charged to the general mass of earth, providing a path for fault currents and holding the parts as close as possible to earth potential This prevents a potential difference between earth and earthed parts, as well as permitting the flow of fault current which will cause the operation of the protective systems [14] The earth system can be classified into three as follows: The TT systems are mostly used in rural areas where the supply is overhead Neutral and earth (protective) conductors must be kept quite separate throughout the installation, with the final earth terminal connected to an earth electrode by means of an earthing conductor [13] TN-S system has a common conductor for the neutral and earth supply The supply is therefore TN-C, with a separated neutral and earth in the consumer s installation it therefore becomes TN- C-S It has the advantage of its fault to earth is also a fault to neutral, therefore creating a high fault current and operating the overload protection rapidly [14] 15 ELECTRICAL SERVICE NETWORK 151 DIVERSITY Diversity in electrical installations permits specification of cables and overload protection devices with regard to a sensible assessment of the maximum demand on a circuit [9] It occurs in an operating system because not all loads connected operate simultaneously at their maximum rating In a bank installation, the diversity factor of lighting is 90% of the total current demand 8

21 while for the power sockets the diversity factor will be 100% of the largest circuit full load current plus75% of the remaining circuit [9] 152 CONSUMER UNITS The consumer unit contains a two-pole switch isolator for the live and neutral supply cables and three bars for the live, neutral and earth terminals The live bar has several fuse-ways or MCBs for overload protection and the selection of the fuse-ways is dependent on the function of the circuit Fuses are rated at 5, 15, 20, 30 and 45 amps while the miniature circuit breakers are rated in accordance with BS EN 60898: Circuit breakers for over current protection for bank installations [9] The figure 16 represents a consumer unit: Figure 16 Eight way consumer and typical contents of a consumer unit The consumer units can be 2way, 4way, 8way, 10way, 13way and 15way depending on the number of fuse-ways or miniature circuit breaker The maximum rating for the consumer units used in the project was 125Amps and was implemented using the two-pole switch [9] 153 DISTRIBUTION BOARDS A distribution board can be defined as a unit that consist of protective devices which protect the circuit from overcurrent It is utilized in a power supply system and it divides three-phase power into balanced loads while providing protection to each of the consumer units connected to it Distribution boards should be selected in a manner such that they provides plenty of wiring space and have terminals of adequate size to accommodate the cable connected to them [18] The 9

22 protection that the distribution board provides for each of the ways is effected by the MCCBs (Moulded Case Circuit Breakers) Figure 17 Distribution board 154 SELECTION OF CABLES The rating of the cable usually depends on its application The size of the cable is usually determined by the amount of current the cable will carry as well as the distance which the cable has to be laid The electrical characteristics of the cable depend on the size of conductors used This determination is done using recommended ampacity and voltage drop values provided in the IEE Standard IEE Standard Power Cable Ampacity Tables Ampacity tables give the size of a conductor, its ampacity and voltage drop Future load growth considerations are important as voltage drop and short circuit considerations may require the use of larger conductors Where non-standard circuits or even special installations are fundamental, the cable specification has to be calculated in the following stages: first, the determination of current flowing; secondly, the selection of appropriate cables and finally, a confirmation that the voltage drop does not exceed 4% 16 DISTRIBUTION SYSTEMS A distribution system is a conductor system, by means of which electrical energy is converted from bulk power sources (generating stations or major substations supplied over transmission lines) to the consumers Distribution systems are divided into 2 systems known as High voltage (primary distribution) and Low voltage (secondary distribution) 10

23 The Distribution systems are important and their planning should be such that their future load growth is made without compromising the quality and economic viability of the installations The two main distribution systems used in large buildings like banks are Ring Distribution and Radial Distribution The rising main supply system is used in high rise offices like banks and flats Copper busbars run vertically inside trunking and are given support by insulated bars across the trunking chamber The supply to each floor is connected to the rising main by means of tap-off units and to balance electrical distribution across the phases, connections at each floor should be spread between the phase bars In order to prevent the spread of fire and smoke, fire barriers are incorporated with the busbar chamber at each compartment floor level The chamber must also be fire stopped to the full depth of the floor [11] 17 EMERGENCY AND STANDBY POWER SYSTEMS An emergency power system is an independent reserve source of electric energy where upon failure or outage of the normal or primary power source, this system automatically provides reliable electric power within a specified time The electric power is provided to critical devices and equipment whose failure to operate satisfactorily would jeopardize the health and safety of personnel or result in damage to property It is usually intended to operate for a period of several hours to a few days Standby Power System is an independent reserve source of electric energy which, upon failure or outage of the normal source, provides electric power of acceptable quality and quantity so that the user's facilities may continue satisfactory operation The standby system is usually intended to operate for periods of a few days to several months, and may augment the primary power source under mobilization conditions [18] Uninterruptible Power Supply (UPS) is designed to provide continuous power and prevent the occurrence of transients on the power service to loads which cannot tolerate interruptions and transients due to the sensitive or critical operations that are undertaken 18 PROTECTION SYSTEMS It is inevitable that faults can occur in electrical systems and appliances that they supply Therefore, steps need to be taken to ensure the safety of power system It is thus necessary to prevent over-current that could cause overheating and fault currents The code requirements have 11

24 to be met to ensure that the equipment and conductors within the system are protected against current flow that will produce destructive temperatures above specified rating and design Overcurrent is defined in the 16th Edition of the IEE Wiring Regulations as a current exceeding the rated value For conductors the rated value is the current-carrying capacity Overcurrent can be divided into two individual levels of fault known as overload and short circuit current Overload Protection: Regulation of the 16th Edition of the IEE Wiring Regulations defines the basic requirement for overload protection as: protective devices shall be provided to break an overload current flowing in the circuit conductors before such a current could cause a temperature rise detrimental to insulation, joints, terminations, or the surroundings of the conductors Circuits shall be so designed that a small overload of long duration is unlikely to occur Short Circuit Protection: Regulation of the IEE Wiring Regulations takes account of the time by applying what is known as the adiabatic equation which states that, the time t in which a given short circuit current will raise the temperature of the conductors to the limiting temperature, can be calculated from the formula [20] 181 DISCRIMINATION Pursuant to the 16th Edition of the IEE Wiring Regulations (BS7671) , this requires that in an installation: The characteristics and settings of devices for overcurrent protection shall be such that any intended discrimination in their operation is achieved Discrimination which is also called selectivity is considered to be achieved when, under fault conditions the circuit breaker nearest the fault operates rather than any of the circuit breakers or fuses upstream of it [20] Current Discrimination: A distribution system requires a circuit breaker to have a lower continuous current rating and a lower instantaneous pick-up value than the next upstream circuit breaker Current discrimination therefore increases as the difference between continuous current ratings increases and as pick-up settings increase between the upstream and downstream breakers Time Discrimination: A distribution system requires the use, upstream, of circuit breakers with adjustable time delay settings The upstream breakers must be capable of withstanding the 12

25 thermal and electrodynamic effects of the full prospective fault current during the time delay For the time discrimination, The total clearing time of the downstream breaker must be less than the time delay setting of the upstream breaker The upstream circuit breaker must have a sufficient withstand capability for the thermal and electrodynamic effects of the full prospective short circuit 19 POWER FACTOR CORRECTION Power factor is defined as the ratio of true power to apparent power, generally expressed as a percentage It is the cosine of the angle between voltage and current in an ac circuit Reactive loads (inductive or capacitive) act on power systems to shift the current out of phase with the voltage A poor power factor will result in excessive losses along utility company feeder lines because more current will be required to supply a given load with a low power factor than the same load with a power factor close to unity It also results in large voltage drop in generators, transformers and transmission lines which results in poor voltage regulation thus extra regulating equipment is required to keep the voltage drop within permissible limits The figure 18 illustrates of a power factor triangle: Figure 18 power factor triangle 110 LIGHTNING PHENOMENON Lightning is the visible discharge of static electricity within a cloud, between clouds, or between the earth and a cloud A Lighting Protection System (LPS) provides a means by which a 13

26 lightning discharge may enter or leave earth without passing through and damaging a human being, electrical equipment or non-conducting structures such as buildings [20] The function of a lightning protection system is to attract a lightning discharge that might otherwise damage exposed and vulnerable parts of a building thereby providing a path of low impedance to an earth safety terminal [9] Zone of Protection: This is the volume of space around a conductor that is protected from lightning strikes The zone of protection around buildings less than 20 metres in height is usually conical but for buildings exceeding 20 metres the zone can be determined graphically by applying a 60 metres radius sphere to the side of a building The volume contained between the sphere and buildings indicates the zone of protection [9] The components of a typical protection system are as given below: Air terminations are provided to intercept a lightning strike and no part of a roof should exceed 5 m from part of a termination conductor, unless it is a lower level projection which falls within the zone of protection The bonding conductor are horizontal conductors running along the ridge of a pitched roof or around the periphery of a flat roof and if the roof is of sufficient size, a 20m* 10 m grid or lattice of parallel terminations should be provided [9] Down Conductor: This is that part of the external lighting protection system that conducts lightning current from the air termination system to the earth terminal system They provide a low impedance route from the air terminations to the earth terminals The down conductor must be installed straight and vertically in order to provide the shortest and most direct path to earth thus the formation of bends must be avoided Earth Termination: This is the part of the external lightning protection system that conducts and disperses lightning current to earth It is required to give the lightning discharge current a low resistance path to earth The maximum test resistance is 10 ohms for a single terminal and where several terminals are used, but the combined resistance should not exceed 10 ohms The figures 18 and 19 give the protection zones for buildings 14

27 Figure 19 Protection zones for buildings <20m height Figure 110 Protection zones for buildings >20m height 15

28 CHAPTER 2 LIGHTING FITTINGS DESIGN AND POWER POINTS DESIGN 21 INTRODUCTION The bank of Fahari City had three floors; mezzanine floor, first floor and ground floor, as shown in the architectural floor plans drawings attached in this section The architectural floor plans drawings were then used to come up with an appropriate lighting scheme through a lighting fittings design and power points layouts on each bank floor plan A schedule of symbols and lighting luminaires settled for in the lighting fittings design and power points layout design were attached Different lighting scheme called for different types of light fittings design based on their aesthetic values, lighting design lumens, saving on costs reasonably and location where they are to be fitted This involved, among other things, avoidance of glare and more positively, conscious attention to colour, form texture, variety and the combined effects of light from natural and electric sources 22 INTERIOR LIGHTING CALCULATIONS FOR THE BANK The number of luminaries in the various open sections and enclosed spaces in the bank at Fahari City are determined using the manual for Interior Lighting Design published jointly by the Lighting Industry Federation Limited and the Electricity Council of Great Britain, Fifth Edition 221 LUMEN METHOD OF LIGHTING DESIGN BOOK ROOM Illuminance 500 lux (IES Code recommendation for such an area) The position of measurement was the desktop Floor area dimensions: L 30m, W 231m Ceiling Height 3m Mounting Height (floor): H 3m-085m215m m Room index K LW H L W m ( + ) 16

29 1 The utilization factor (UF) was obtained from the table of utilization factors versus the room index for a 2x14W recessed modular cinqueline with louvre optics having a DLOR of 65% For a room of K 061 and ceiling and wall reflectances of 07 and 05 respectively, the utilization factor (UF) is, by interpolation: Illuminance Installed lux UFMF Area Installed flux lumens 4*14W recessed modular cinqueline with perforated panel mirror brite louvres are used, each tube has a known Lighting Design Lumen (LDL) output of 4800 lm No of fittings 4 The lighting layout for the book room was as shown in figure 21: Figure 21: Light fitting design for the book room 17

30 The lighting design for the ground floor was summarized in the table 21: Table21: lighting design for the ground floor Ground Floor Illumi nance, lux Type of light fitting Area, m 2 Maintenance Factor, M Utilization Factor, U Lumens Meeting Room 500 Recessed modular Book Room 500 Recessed modular Operation Recessed 300 Manager modular Strong Room 500 Primata Bank manager s Recessed 500 office modular ATM Lobby 150 Recessed modular Washrooms 150 Danube No of fittings 223 POWER SOCKET DESIGN In domestic power socket design, an unlimited number of sockets can be connected in a ring circuit for a floor area 100 and this design was also applied in the design of a bank, where the sockets were applied for public use The type of sockets applied were twin sockets, the power drawn from four twin sockets was (32 240) Watts This design was made considering future load growth of 120% of the current demand and the use of the twin circuits was to minimize overloading Non-domestic buildings like the banks had basic requirements for switches, outlets and controls that were conventional and familiar plus contrasting in colour to their surroundings Large push pad were preferred or extra wide rocker switches and pictogram to clarify use and purpose where multiple switches occurred The diversity factor according to the 16 th Edition of the IEE for the ring circuits was taken as 100% for the first ring and 75% for the subsequent ring circuits 18

31 The power points for the book room were as shown in the figure 22: Figure 22: Power points design for the book room 19

32 ELECTRIC SERVICES DISTRIBUTION CHAPTER 3 A count of the light fittings and power points was established on each floor per phase The total load per phase was then calculated to facilitate determination of the number of consumer units (CUs) and distribution boards (DBs) to be used in supplying each floor and each phase The CUs and DBs were located for safety and the convenience of supplying the loads Their distances from the DBs supplying them was measured and so was the distance of the various DBs from the switchboards determined The fittings were then assigned to be supplied by the various CUs by means of circuiting Total current for a group of lights switched on by a single switch was not to exceed 5 Amperes, this being the limiting value current that an ordinary switch s contacts could repeatedly make or break without risking excessive burning that would shorten the service life of the switch Putting a worst case, that is the upper limit of 100W on each light fitting supplied at 240 V implies: Current drawn / Maximum number of fittings per switch In this work, the maximum load assigned per CU was not to draw current more than 125 amperes CU load of 70A-100A was adopted for the bank floor (ground floor) with the heaviest load a while a CU load of 55A-60A was adopted for the bank floor (Mezzanine floor) with lighter loads In the design of the lighting and distribution of the bank, the following design specifications were taken into consideration: Light fittings - A worst case of 100W was assumed for all the light fittings that did not exceed that amount Socket outlets - A power of (32 240) watts was assumed, a maximum value was chosen as the loads to be used on the sockets could not be assumed Single phase isolators - This included the fans and the hand-driers The hand-driers were used in the washrooms A load of 1500watts was assumed for each hand-drier 20

33 Three-phase isolators - The lift is an example of a three phase isolator A maximum current of was assumed A power of approximately was assumed as the maximum average power that would be drawn by a lift Kitchen unit - This was used for the cooker; the bank had a cooker unit of 1500W 31 LOAD BALANCING Load balancing was an important aspect of power distribution that was done to ensure that the total load on the different phases of the three floors was approximately equal Thus whenever a fault occurred on any particular floor on a particular phase, it only affected the phase that the fault had occurred on and not the entire floor Each floor was divided into 3 phases; red, yellow and blue and a calculation was done to ensure that the total load for each phase was approximately equal This was so because the power in the building was supplied through a three phase system The phase that was assigned the larger overall load on one floor was deliberately given a lesser load on the next floor This had an overall effect of approximately balancing the load on the three phases The implementation was as shown in table 31 Table 31: The total load with diversity on the Mezzanine floor-red Phase MEZANINE FLOOR (RED) LIGHT FITTINGS Fitting type No of Diversity Assumed rate Total load (watts) fittings factor (Watts) Type Cinqueline Type D Type 2D Ring socket Fans Hand drier LIGHT FITTINGS POWER POINTS TOTAL (WATTTS) 19020W 21

34 The diversity factors were pursuant to the 16 th edition of the IEE regulations The total load for blue phase of the mezzanine floor + Therefore the total current drawn by lower floor loads The load current was 793amps; logically 1 consumer unit (CU) with an integral isolator rated 100A will be required Table 32: The total load with diversity on the Mezzanine floor-yellow Phase MEZANINE FLOOR (YELLOW) LIGHT FITTINGS Fitting type No of fittings Diversity factor Assumed rate (Watts) Type Cinqueline POWER POINTS Ring circuit Ring circuit Fans TOTAL(WATTTS) Total load (watts) The diversity factors were pursuant to the 16 th edition of the IEE regulations The total load for yellow phase of the mezzanine floor + Applying 20% future load growth the total load for the yellow phase of the mezzanine floor: the total current drawn by the yellow phase of the mezzanine floor was 771A A standard consumer unit allows a maximum load of 100A For a current of 771A amps logically 1 consumer units (CUs) will be used 22

35 Table 33: The total load with diversity on the Mezzanine floor - Blue Phase MEZANINE FLOOR (BLUE) LIGHT FITTINGS Fitting type LIGHT FITTINGS No of fittings Diversity factor Assumed rate (Watts) Type Cinqueline Type D EXIT POWER POINTS Ring circuit Ring circuit Fans TOTAL (WATTTS) Total load (watts) The diversity factors were pursuant to the 16 th edition of the IEE regulations The total load for red phase of the mezzanine floor + Therefore the total current drawn by the red phase of the mezzanine floor A standard consumer unit allows a maximum load of 100A For a current of 826 amps, logically 1 consumer units (CUs) will be required In a similar way, calculations were done to determine the load per phase for the ground and first floor and tabulated in table 34 From the table 34, balance was approximately achieved between the three phases though a small deficient was evident 23

36 Table 34: The summary of the total loads of all the floors of per phase RED YELLOW BLUE GROUND FLOOR MEZZANINE FLOOR FIRST FLOOR TOTAL LOAD(WATTS) CURRENT(AMPS) A COMPLETE CONSUMER UNIT SPECIFICATION A summary of the number of CUs in their different floors and phases and their arrangement was as shown in table 35: Table 35: Consumer Unit Specification Floor Phase Load Current No of CUs Arrangement GROUND R (Watts) drawn(amps) 1355 CUs 2 CU GFR1,CU GFR2 FLOOR Y CU GFY1,CU GFY2 B CU GFB1,CU GFB2 MEZZANINE R CU MFR1 FLOOR Y CU MFY1 B CU MFB1 FIRST FLOOR R CU FFR1,CU FFR2 Y CU FFY1 B CU FFB1,CUFFB2 TOTAL CUs 24

37 33 CONSUMER UNIT DESIGN There were a total number of fifteen consumer units and every CU had circuits which were assigned to a given way This was done by assigning each of the lighting or power socket circuits to a given way in the CU The standard sizes for miniature circuit breakers by MEM catalogue are 6A, 10A, 16A, 20A, 32A, 40A, 50A and 63A A sample was done for the ground floor, the red phase GROUND FLOOR (RED PHASE) CIRCUIT CIR GFR 11 CIR GFR 11 means that the single phase loads were assigned to the first consumer unit on ground floor and on the red phase, CU GFR1The way assigned to them on the CU was way 1Thus the assignment of fittings on this CU way was summarized in table 36 Table 36: The assignment of fittings on CU GFR1 way 1 Fitting type No of fitting Assumed Total load(watts) rate(watts) Type L Total load(watts) 800 Therefore current drawn by the assignment of the type L fittings on circuit CIR GFR 11 A 6A MCB was used to protect the CIR GFR11 From the IEE tables attached in the appendix, the two cables single phase, cable was settled for which carried a maximum of 175 Amps In a similar way, the MCB ratings for the circuit CIR GFR12 on way 2 and circuit CIR GFR13 on way 3 were determined These circuits were lighting circuits; 6A MCBs were used for their protection against fault currents From the IEE tables attached in the appendix, the two cables single phase, cable was settled for which carried a maximum of 175 Amps 25

38 CIRCUIT CIR GFR 14 CIR GFR 14 means that the single phase loads were assigned to the first consumer unit on ground floor and on the red phase, CU GFR1 and the way assigned to them on the CU was way 4 Thus the assignment of fittings on this CU way was summarized in table 37 Table 37: The assignment of fittings on CU GFR1 way 4 Fitting type No of fitting Assumed Total load(watts) rate(watts) Ring circuit Total load(watts) 7680 Therefore current drawn by the assignment of the ring circuit 2 on circuit CIR GFR 14 A 40A MCB was used to protect the CIR GFR14 From the IEE tables attached in the appendix, the two cables single phase, cable was settled for which carried a maximum of 41Amps In a similar way, the MCB rating for the ring circuit GFR15 on way 5 on the first consumer unit on ground floor was determined A 40A MCB was used for protection against fault currents From the IEE tables attached in the appendix, the two-core single phase cable was settled for which carried a maximum load current of 41Amps CIRCUIT CIR GFR 16 CIR GFR 16 means that the single phase loads were assigned to the first consumer unit on ground floor and on the red phase, CU GFR1 They were assigned on way 6 of the CU Thus the assignment of fittings on this CU way was summarized in table 38 26

39 Table 38: The assignment of fittings on CU GFR1 way 6 Fitting type No of fitting Assumed Total load(watts) rate(watts) Fan Total load(watts) 1500 Therefore current drawn by the assignment of the fan on circuit CIR GFR 16 A 10A MCB was used to protect the CIR GFR1 From the IEE tables attached in the appendix, the two-core cables single phase cable was settled for which carried a maximum of 24Amps In a similar way, the MCB ratings for the Circuit CIR GFR17 on way 7 and CIR GFR18 on way 8 were determined These circuits had fans and used 10A MCBs for protection against fault currents From the IEE tables attached in the appendix, the two-core cables single phase cable was settled for which carried a maximum load of 24 Amps Two spare ways were added giving a 10-way CU with an 80A integral isolator The overall design specifications for the first consumer unit on the red phase of ground floor (CUGFR1) were summarized in the table 39 27

40 Table 39: Overall design specifications for the first CU on the red phase of ground floor (CUGFR1) Circuit and way on CU Fitting type Total load(watts) Total current (amps) MCB size(amps) Cable size ( ) GFR 11 GFR 12 GFR 13 GFR 14 Lighting Lighting Lighting Ring circuit circuit circuit circuit GFR 15 GFR 16 GFR 17 GFR 18 Ring Fans Fans Fans circuit A 6A 6A 40A 40A 10A 10A 10A The first consumer unit on the ground floor, red phase-consumer unit GFRI was a 10-way consumer unit and it had an integral switch rated 80AFrom specifications given, the consumer unit, CU GFR 1 is designed incorporating the circuit ways and including two spare ways for future load growth as shown in figure

41 6A CIR GFR11 3 x 15 mm 2 PVC- SC- CU Cables - Lighting 6A CIR GFR12 3 x 15 mm 2 PVC SC CU Cables - Lighting 6A CIR GFR13 3 x 15 mm 2 PVC SC CU Cables - Lighting 40A CIR GFR14 3 x 60 mm 2 PVC SC CU Cables Ring socket outlets 40A CIR GFR16 3 x 60 mm 2 PVC SC CU Cables Ring socket outlets 80A 10A CIR GFR17 3 x 25 mm 2 PVC SC CU Cables - Fan 10A CIR GFR18 3 x 25 mm 2 PVC SC CU Cables - Fan 10A CIR GFR19 3 x 25 mm 2 PVC SC CU Cables - Fan CIR GFR19 CIR GFR110 Spare Spare CU GFR1-10way Figure 310 Consumer Unit (CUGFR1) - 10way In a similar way, design analysis was done for all the other consumer units located on the blue and yellow phases of the ground floor, mezzanine floor and first floor The analysis was summarized in appendix D 331 SIZING OF CU CABLES CABLE FEEDING CONSUMER UNIT CU GFR 1 The total single phase loads of the CU GFR 1 (First consumer unit on the red phase of the ground floor) with the diversity factors being considered was as shown in the table

42 Table 310: Total load for the first consumer unit on the red phase of the ground floor (CUGFR1) Fitting type No of fitting Diversity factor Assumed rate(watts) Total load(watts) Type L Type Type Cinqueline Type Cinqueline Ring circuit Ring circuit Fan Fan Fan TOTAL The total single phase loads of the CU GFR 1 are: Applying 20% future load growth: The design current was therefore Length of cable to feed the CU GFRI from the Distribution board, (DB A) located on the ground floor 69m From IEE tables attached in the appendix, the 25 2-core single-phase cable of a voltage drop rate of 18 mv/a/m seemed appropriate which carried up to 101A amps Allowing up to a maximum of 15% voltage drop (the maximum voltage drop allowed for the design between a DB and CU) on this cable to supply this CU from the DB The cable choices for a circuit had to carry a larger current than the design but smaller than the cable capacity Therefore an overload device had to be rated at a figure between the two (cable capacity and design current) so that it 30

43 would trip to protect the cable but would not operate under normal conditions Therefore it was prudent to calculate the voltage drops of the CU cables using the MCCB ratings This was undertaken as shown: % _ % Therefore the voltage drop was given as: % / / % 0414% 0414% < 15% requirement, 25mm2 non-armoured twin cable was decided upon In a similar manner the voltage drop was calculated for the remaining CUs and the results were tabulated in the appendix F 34 DISTRIBUTION BOARD SPECIFICATION In the determination of the number of distribution boards (DBs), it was important to consider the total load that was supplied by the three floors The distribution boards were to supply all the 15 consumer units with the single phase loads as indicated in the table 35, section 32 A DB load with a maximum of 630Amps design line current was adopted in the bank project The total single phase load of all the 15 CUs as per the table 35 was given by: The line current drawn by the total number of 15 CUs supplied by a three phase DB with a line voltage of 415V: The design current for the DB was 630A, Therefore the 15CUs with all the single loads of the three floors of the bank could be supplied by one DB This was designated as DB A and was 31

44 therefore placed at the ground floor of the bank This was represented as shown in the AutoCAD drawings The distribution board was three phase, therefore the consumer units were placed in the three different phases 341 SIZING OF THE CABLE FEEDING DISTRIBUTION BOARD A DB A supplied CUs GFR1, GFR2, GFY1, GFY2, GFY3, GFB1, GFB2, MFR1, MFY1, MFB12, FFR1, FFR2, FFY1, FFB1,FFB2 CUs GFR1, GFR2, MFR1, FFR1 and FFR2 had a total load of 79620W as per the table 35 and were on the red phase (see section 32) Applying 20% future load growth: DB current on the red phase 3981 A GFY1, GFY2, GFY3, MFY1 and FFY1 were on yellow phase and had a total load of Watts (see section 32) Applying 20% future load growth: DB current on the yellow phase 4134A CUs GFB1, GFB2, GFY3, MFB1, FFB1 and FFB2 were on blue phase and had a total load of Watts (see section 32) Applying 20% future load growth: DB current on the blue phase 4054A Length of cable connecting DB A to the switchboard 148m Current used for sizing the cable 4134 Amps (the largest of 3981A, 4054A and 4134A) Calculation of the voltage drop was done using the MCCB rating to ensure the protection of the cable when a fault occurred It also ensured that not too large a conductor was used to size the cable feeding the DB The MCCB used was rated 500A Allowing for a maximum of 15% voltage drop on this cable: 32

45 % _ % % voltage drop // % % 03298% voltage drop meant that the 300mm 2 ; 3or 4 core cable settled for was appropriate The figure 31 represents DB A supplying the 15 consumer units Figure 31 Distribution Board A 33