BN3232 Design report EE

University of Central LancashireBEng (Hons) Building Services EngineeringModule: BN3232 – System Design Design Report for Electrical Installation______________________________________________________________________________________CONTENT

1.0 Building Information

2.0 Description of Building Site Map

3.0 Design Main Theme

4.0 Regulations & Standards

5.0 Electrical System Design

5.1 Power Distribution System of Composite Building5.1.1 Nature of Supply5.1.2 Distribution of Loading among Transformers5.1.3 Customer’s Main Switch (Main Incomer Circuit Breaker)

Requirements5.1.4 Changeover Arrangement for Emergency Supply5.1.5 Rising Mains Arrangement5.1.6 Earthing Requirements5.1.7 Power Supply Company’s Meter Arrangement5.1.8 Power Factor Correction5.1.9 Plant Room Arrangements5.1.10 System Protection5.1.11 Equipments Selection Consideration & Arrangement

on Main Incoming, Main Circuit, Sub-Main Circuit & FinalCircuit

5.2 Standby Power (Emergency Generator Set) System5.3 Lighting System5.4 Earthing System5.5 Lightning Protection System5.6 Doorphone & Security System5.7 CABD/SMATV/CATV System5.8 CCTV surveillance System5.9 Public Address system5.10 Telephone/Communication System

6.0 Special Design Consideration6.1 Presence Detector for Office Lighting Control

7.0 AppendixA Load AssessmentB Generator Set Size AssessmentC Calculation of Fuel Oil Tank SizeD Sample Cable Sizing CalculationE Calculation for Capacitor Bank Sizing AssessmentF Lightning Protection Design System and Lightning Risk

Assessment

University of Central LancashireBEng (Hons) Building Services EngineeringModule: BN3232 – System Design Design Report for Electrical Installation______________________________________________________________________________________

8.0 Drawings

Drawing no. DescriptionEL-01 Schematic Diagram for Electrical InstallationSD/GBP/01 Ground Floor Layout PlanSD/GBP/02 First Floor Layout PlanSD/GBP/03 Second Floor Layout PlanSD/GBP/04 3/F~19/F Layout PlanSD/GBP/05 Roof Floor Layout Plan

9.0 Reference12.1 Code of Practice for Energy Efficiency for Electrical

Installation 1988Edition

12.2 Code of Practice for the Electricity (Wiring) Regulations1997 Edition

12.3 General notes/hand outs for Electrical Services from Year1 to 3.

University of Central LancashireBEng (Hons) Building Services EngineeringModule: BN3232 – System Design Design Report for Electrical Installation______________________________________________________________________________________1. Building Information

The proposal building which situated at the south-east side ofKwai On Road a in Kwai Chung. The building is composed withcommercial center (G/F –2/F) and office(3/F – 19/F) and MechanicalPlant Room located at roof floor.

2. Description for Building and Site Map

2.1.

Figure. 1 – Site Map

2.2. This presentation is briefly describe the basic provisions,design concept, system design criteria and consideration of thebuilding services including:- MVAC system- Electrical system- Vertical Transport system.

3.0 Design Main Theme

Safe, comfortable and reliable environments are main designrequirements for the building occupants because they can directlyinfluence the human activity and the public health. In the worstcase, it may affect the organization productivity and cause economicloss.

In fact, Power Surge is one of the major problems we oftenencounter. It can seriously influence our equipments inside apremise.

The need for Surge Protection

- Lightning is a fascinating natural phenomenon and can hardly beescaped.


There are mostly two ways in which lightning can interact withelectronic equipment in a building:-

(a) By a Direct Strike from a cloud-to-ground lightning stroke.This describes a direct strike to the equipment or more usually,the building or plant housing it. The effects of this can bedevastating, due to the enormous currents and energy involved.Where there is a significant risk of a direct strike, externalstructural protection based on lightning conductors and earthrods is essential to provide a relatively easy path for lightningcurrent to flow into ground without entering the building.Without external protection, equipment housed in the building mayprovide the easiest path to earth for lightning currents via‘side-flashing’ where the lightning arcs across from the outsideto the inside, damaging the structure and the equipment inside.

(b) Ground potential surges caused by a cloud-to-ground strike orsometimes referred as ‘resistive coupling’.When lightning strikes the ground, the current disperses throughthe soil. Because the ground is not a perfect conductor, highvoltages can develop. Two building and the equipment which theycontain, can therefore be at very different local groundpotentials. If cables buried or not, link them, the equipment ateach end will be subjected to this potential difference. This isa common source of damage. The ground potential surge will bemost severe in the case of direct strike. Although direct strikes causemost damage, the ground potential surge poses the greatest threat to electronicequipment because the probability of it happening is much higher.

- The mains supply is also likely to carry disturbances withina building caused by switching of heavy current devices such asmotors and etc. Transients can be introduced into a system bythe mains supply (as with any others cables).

In our lighting design, for the sake of energy saving, each officeis designed be equipped with a presence detector to turn off the officelightings when unoccupied or with adequate daylight. The processfrom frequently switching on and switching off, will thus introducesurge.

It is therefore necessarily need to carry out surge protection to protectour delicated equipments in a building.


Methods of Surge Protection

- By earthing, i.e. bringing all incoming services such as electricalcables, telephone/communication cables, antennae cables, metallicwater and gas pipes into the building at one point, bonding allthese services to the main earthing terminal in the main switchroom. The conventional power supply distribution system for thisbuilding is something as shown in Figure 4. For example, theincoming power cables includes three phases and the neutralconductor, with the provision of an earth bar between the switchroom and the transformer for the purpose of connection of allexposed conductive parts of consumer installation to CLPtransformer earth. In fact, this is defined as a TN-S system.If all the equipments are bonded to this point, no relativelyvoltages are generated and no currents will flow through thepersonnel or distribution system.

- By means of fitting with Surge Protection Devices (SPD) on all incoming cables for the allabove services and bonding the SPD to the earth terminal.

Surge protection device should ideally operate instantaneously todivert a surge current to ground with no residual common modevoltage presented at the equipment terminals. Once the surgecurrent has subsided, the SPD should automatically restore normaloperation and reset to a state ready to receive the next surge.

Surge protection device can limit the transient voltage to alevel which is safe for equipment they protect by conducting thelarge surge current safely to ground through the earth conductorsystem. Current flows past, rather than through, the protectedequipment and the SPD thereby diverts the surge. One way ofregarding a surge protection device is as an earth connectionwhich is only present during a surge.

For lightning, Data line SPD and power line SPD are installed at the roof of the locationof the CABD/SMATV antennae to eliminate the surge of lightning.

With the aid of above means of protections, delicated equipments inour building can be safeguard from surges.

4.0 Regulations & Standards

(a) The Supply Rules and the Installation Guide of the Power SupplyCompany


(b) Electricity Ordinance 1990 and Code of Practice for TheElectricity (Wiring) Regulations 1997 issued by EMSD.

(c) BS7671:1992 for Electrical Installation by the Institution ofElectrical Engineers, United Kingdom.

(d) Guide to Supply and Metering Arrangement on Customer’s InternalDistribution System by CLP

(e) Commercial Code of Practice 215-Load Assessment Procedurepublished by CLP

(f) Codes of Practice for Minimum Fire Service Installations andEquipment in June 1998

(g) Code of Practice for Energy Efficiency of ElectricalInstallations 1998 Edition.

(h) British Standards Specification(i) Building Ordinance (Chapter 123) (j) Building (Lifts) Regulations Cap123(k) Building (Escalators) Regulations Cap123(l) Code of Practice on Works for Lifts and Escalators(m) Code of Practice on The Design and Construction of Lifts and

Escalators(n) Lifts and Escalators (Safety) Ordinance Cap327(o) Code of Practice on The Examination, Testing and Maintenance of

Lifts and Escalators(p) EPD Requirement(q) Regulations of the Telecommunication Authority, Government of

Hong Kong(r) Hong Kong Radiation Board(s) Laws of Hong Kong – Telecommunication (Cap.106)

5.0 Electrical System Design

The building is fed by CLP’s transformers in transformer rooms.Transformer room has two transformers with rating of 1500KVA each.

L.V. switchboards located at main switch room at Ground Level.Switchboard serves the shops, restaurants, office tenants powersupply as well as the public services. The switchboards are equippedwith ACBs, isolating switches, fuse switches, MCCBs, meters,protection relays and control circuit accessories.

The main and sub mains distribution systems comprising cablefeeders, isolating switches, MCB/MCCB distribution boards, busbarchambers, conduit, trunking and etc.,

At Roof Level, there is one unit 450KVA diesel generator set to backup the essential power of the whole composite building.


The commercial tenants are fed by one 400A TPN Cu. busduct with tee-off at each floor respectively at each electrical riser duct/switchroom.

The population of the building is served by 7 unit lifts. All liftcars are closely monitored by CCTV system.

All the antennae for CABD/SMATV are located at the roof top.Shop arcade and public lobby and corridor are provided with P.A.system.

For energy saving purpose, the lightings at public circulation areaof the residential block, carpark, vehicle road, etc are controlledby building management system at control room and at level of openarea with landscape lightings controlled by timer and photo cell.

At office block, the facilities of flushed floor trunking system areprovided at each tenant.

5.1 Power Distribution System of the Building

The L.V. incoming supply is taken from the L.V. terminals of powercompany’s transformer through the multi-cable transit (MCT) insidethe partition wall between transformer rooms and L.V. main switchrooms.The building requires two units of 1500KVA transformers. Accordingto CLP’s sub-station design booklet requirement, one transformerroom is required in this building.

5.1.1 Nature of Supply

According to CLP Power Supply Rules, the supply system operatingvoltages and frequency are as follow respectively:-

Three Phase 380V ±6%Single Phase 220V±6%Frequency 50Hz±2%

5.1.2 Interconnection Facilities of Customer’s Installation

Customer’s installations are directly connected to transformers viamulti-cable transit. CLP’s power cables are connected to the LVSwitchboards through through cable trench at Ground Level.

All interconnecting devices, Incoming ACB including the bus-sectionACB are of 4-pole type with mechanical interlock.


Castell key interlock serves this kind of mechanical interlock.

5.1.3 Customer’s Main Switch (Main Incomer Circuit Breaker) Requirements

Owing to the supply voltage has changed from 346V to 380V,transformer rated output current was then changed to1500kVA /√3/380V = 2,279A at 380V supply system, the building’s mainswitch adopted is 2,500A 4 Pole Air Circuit Breaker and so is set at2,250A.

Since the power supply is directly drawn from transformer, the MICBmust be of Draw-out type and its short circuit breaking capacity israted at 55kA (>40kA, as required by CLP requirement).

It also incorporates the following functions:-isolation and switching.-protection against overcurrent by means of overcurrent protection

relays.-protection against earth leakage by means of earth protection

relays.

5.1.4 hangeover Arrangement for Emergency Supply

1 set of 250Pole ATS (Automatic Transfer Switch) is connected to theEmergency Generator for Emergency supply, such as essentiallightings, F.S. pumps and other fire fighting equipments in order tosuit with F.S. requirement.

In addition, a test switch is provided to simulate the main powerfailure and initiate the changeover sequence to allow on loadtesting.

After restoration of normal supply, the ATS need to manuallyrestored to its normal position.

In case of power failure is sensed by the under volt relay, it willactivate the diesel generator set to start up within 15 second andtransferring essential power via the ATS to the essential section ofthe L.V. switchboard to maintain the operation of the building.

In case of fire signal or low fuel of the generator set is received when the generator isrunning, a control relay is equipped to trip some unnecessary loading, such as A/C system.(we refer them as categories 2 loads). By doing so, we can reduce the burden(load) of thegenerator.


5.1.5 Rising Mains Arrangement

Since any building of more than four floors including the groundfloor and designed for occupation by more than one customer shall beprovided with 3-phase electrical rising mains with 3-phase andneutral tee-off at each floor. The rising mains for tenants arearranged as follow:

- One set of 400A TPN Cu. busduct riser for commercial tenants from3/F to 19/F.

Each rising main installation is designed with 3-phase 4-wire fullneutral, equipped with a protective device for overcurrentprotection by Moulded Case Circuit Breaker (MCCB c/w built-inoverload) with a short circuit breaking capacity of rated at 25kAand for earth fault protection by means of an individual IDMT EarthFault relay.

A local riser switch is also provided in each floor for isolation,switching and overload protection.

5.1.6 Earthing Requirements

- The building is provided with its own earthing system. Theearthing pits are located at Ground Level.

- The customer’s main earthing terminals are bonded to thetransformer earth via a 38mm x 6mm copper bar located on the wallbetween the main switch room and transformer room on GroundLevel. As the bonding conductor shall not be smaller than 150mm2, so we use a 6mm x 25mm copper tape.

- The cross-sectional area of riser earthing conductors are of 70mm2 copper tape.

- A separate earthing system is also provided for the generator setand are linked to he building’s main earthing terminal by meansof 3x25mm copper tape.

- Separate earthing system should be provided for telecommunication/ computer equipment.

5.1.7 Power Supply Company’s Meter Requirement


Meter Position is located on individual floor electrical meter roomnear the rising mains tee-off position. At the meter position, alocal switch is provided for disconnecting the meter equipment fromsupply.

5.1.8 Power Factor Correction

Since if the total loading of a customer exceeds 25kW, then thepower factor of the customer should not be fall below 0.85 lagging.Otherwise, capacitor bank should be added to correct the powerfactor to not less than 0.85 lagging. Therefore, 300kVAr powerfactor correction equipments are provided not only for building’scommunal supply but also for each incomer ACB as well. Power factorcorrection equipment is divided into 6 steps, with each step rangingfrom 50 KVAr.

5.1.9 Plant Room Arrangements

Plant rooms provided for electrical services in this compositebuilding mainly include:-

- 1 nos. of Transformer Rooms- 1 no. of Main Switch Room - 1 no. Generator Room- 1 no. Chiller Plant Room for MCC

Transformer Room

It located on Ground Level, which is easily accessible.All electrical installations inside the transformer room must followthe transformer room layout as issued by the power supply company,CLP.

Main Switch Room

The main switch room is directly adjacent to the transformer room.There are two main switchboards in the composite building.One is mainly for Air-conditioning system (Motor Control Centre) atGround Level while the other are for tenant power supply for shops,office and apartments as well as communal (public) services powersupply of the whole composite building.


Generator Room

Generator room is located on Roof Level. A fuel tank room is justnext to the Generator Room.It serves the emergency power supply for the composite building incase of normal power failure or fire.

Chiller Plant Room

Chiller Plant Room is also located on Roof Level.There are two MCCsinstalled inside the plant room, one is fed from normal supply, theother one is fed from essential supply for maintaining a certainextent of A/C to tenants in case of normal power failure.

5.1.10 System Protection

The protective devices include IDMT relays, fuse, moulded casecircuit breakers (MCCB), miniature circuit breakers (MCB) andoverload (thermal) relays for motor circuits protection.

In this building design, the system protection include:

- Overcurrent protection;- Fault protection (earth fault, single phase fault, two phase

fault and three phase fault);- Protection against direct contact; and- Protection against indirect contact

Overcurrent Protection

This is to protect the circuits from being overloaded. Theovercurrent device at the main incoming position is normally an IDMTrelay. Power supply company specifies that it should operate equalto or faster than the ‘maximum time – current characteristic curveof consumer L.V. overcurrent protective relays as shown in theGrading Time Requirement allowed for Main Breaker disconnectiondiagram from Appendix.

Fault Protection

There are four types of short circuit faults:- Earth fault- Single phase short circuit fault- Two phase short circuit fault- Three phase short circuit fault


For Earth fault

In the event of earth fault, the system should be able to disconnectthe supply automatically within 5 seconds. To achieve this, theprotective device should be well co-ordinated with the earthingsystem. If the earthing resistance is low enough, earth faultprotection can be achieved by fuse, MCCB or even MCB. For earthfault protection at main incoming position, usually IDMT relay isused which had adjustable sensitivity and response time.

Phase Short Circuit Faults

There are single phase fault, two phase fault and three phase fault,of which the three phase (symmetrical) fault is the most severe one.Therefore, in our calculation sheets, we only consider the threephase short circuit current. In fact, when calculating prospectiveshort circuit current, it is the three phase fault that isconcerned. Again, we use IDMT relays, fuse, MCCB and MCB for thesefault protection in our design. Sometimes if the fault level is notsure at any points of the installation, it is safe to use fusebecause HRC fuse (BS88) can withstand a fault level of 80 KA andthat’s why we mostly use F/S in our system protection design.

Protection Against Direct Contact

Since this is to prevent the direct contact between human beings andlive parts of the installation. To achieve this, all equipments weselected are required to have such provision such as suitablebarriers, segregation and insulation to prevent direct contact.That’s why we design electrical switchgears are normally placed atplant rooms such as electrical switch rooms because they can be outof reach by unauthorized person. Protection Against Indirect Contact

It concerns with the ‘Touch Voltage’ that is experienced by humanbeings in touch conductive parts normally not carrying current butbecome ‘live’ at faulty situation.

In this building we adopt protection against indirect contact by:-- Equipotential Bonding - Automatic disconnection of supply by means of - Earth Fault Protection relays (within 5sec. for fixed

installation)- RCD (within 0.4sec.for socket outlets)


This method is normally used in HK. By this method, all conductiveparts within the building are electrically bonded together to ensure‘ equal potential’. For fixed equipment, the disconnection time is achieved by carefullyselecting and setting the rating and sensitivity of IDMT relay,MCCB, fuse and MCB. For socket outlet circuit, the disconnection time is achieved byusing RCD of 30 mA sensitivity.

5.1.11 Equipment Selection Consideration & Arrangements on MainsIncoming, Main Circuits, Sub-main Circuits & Final Circuits

Mains Incoming

Main Incoming ACB used is of 4 Pole, horizontally draw-out type,conform to BS EN 60947-2 :1992 and rated at 55kA(normally in marketfor most brands) and certified by type tests by ASTA. We adopt 3nos. of 2250/5A P.C.T.s (5P20) for the tripping or operation ofprotection relays You may ask why the accuracy class and limit factor for protectioncurrent transformer chosen is 5P20. In fact, we are mostly concernedwith the latter figure 20, (i.e. the accuracy limit factor) becauseit will affect the accuracy of the C.T. output, which in turn willindirectly affect the proper operation of a protection relay. For example, when a fault level of 40kA, for a rated primary currentof 2,250A, the ratio is 40kA/2,250A = 17.8 (< 20), and the accuracycan be maintained. However, if we select a lower accuracy limitfactor, say 15, it may probably exceed the C.T. accuracy limit forthe same fault level, and accuracy will no longer be maintained. Under such circumstances, the protection relay may not sense thefault current correctly and thus it will not operate. Therefore itis very dangerous. That’s why we have to consider the latter figurewhen choosing a protection current transformer. In addition, 7 nos. of protection current transformers (rather than4nos. traditionally in the past) are so arranged (3 nos. forovercurrent, 4 nos. for earth fault) for reducing the burden of eachPCT such that it is ‘strong’ enough or adequate to drive the relays.So a low burden CT is preferred for selection.

Main Outgoing Circuit from the L. V. Switchboard


For circuits above 500A TPN, ACB are used. Overcurrent and faultprotection are achieved by IDMT (1.3sec.) relays.

For circuits 500A TPN or below, Fuseswitches (F/S) conform BS EN60947-3:1992 are used. Overcurrent and fault protection are achievedby fuses ( to BS88:part 2).

For circuits 500A TPN or below which require the use of IDMT relayto ensure fast disconnection time in case of earth fault, MCCB areused for overcurrent and fault protection.

IDMT relay used is of (0-1.3sec.) characteristics (i.e. for 10 timesmultiples of fault current setting, it will operate at 1.3sec.) withadjustable currents setting (between 50% to 200% for overcurrent)and (between 10% to 40% for earth fault), in seven equal steps,comply with BS 142 and CLP requirement.

Fuse adopted comply with BS88:part 2 (of breaking capacity 80kA) isadequate for a maximum prospective short circuit current of 40kA.Submain Circuits

MCCB (25kA) or Fuse (BS88) are used, overcurrent, earth fault andshort circuit protection is achieved by the MCCB or Fuse.

The instantaneous tripping time (from Time/Current characteristicsof MCCB) is 0.1sec. at 10 times of rated current which means that itoperates faster than the upstream protective device. Thereforediscrimination are well coordinated between downstream and upstreamprotective device.

Final Circuits

MCB used are of triple pole or single pole and conform to BS EN60898:1991with a tripping classification of Type C for all lightingand power circuits with short circuit breaking capacity of 6kA (M6)is used; overcurrent, earth fault and short circuit fault protectionis achieved by the MCB.

In addition to MCB, socket outlets are protected by RCD (30 mAsensitivity) for earth fault protection

For motor circuits, MCB or MCCB are used for earth fault and shortcircuit fault protection but depending on the motor rating (thelargest MCB is rated at 100 A); thermal overload relay with timedelay are added for overcurrent protection.


Using the adiabatic equation K2S2 ≧I2t , provided by IEE WiringRegulation, we can easily determine whether a given rating of MCBunit can protect the cables.From the maximum I2t (energy let through) / prospective fault currentcharacteristic for a given rating of MCB, if at a point theprospective fault current touches the MCB curve is below the figurefor chosen cable’s K2S2 operating limit, then cable chosen is enoughfor protection.

The instantaneous tripping time (from Time/Current characteristicsof Type C MCB) is 0.1sec. at 10 times of rated current. It impliesthat it operates faster than the upstream protective device.Therefore discrimination are well coordinated between downstream andupstream protective device.

Power Cables

Most of power cables used are of XLPE/SWA/PVC copper cable to BS5467due to its high operating temperature up to 90℃ and high currentcarrying capacity than PVC insulated cable. Fire resistant cableused are of FR/XLPE/SWA/LSF to BS6387 Cat CWZ. and IEC 331(750℃for 3 hours).Prefabricated main and branch cross-linked XLPE/PVC cable complywith IEC standard 502 are used for tenant cable riser. The advantageof using this cable is high quality and simple and easy forinstallation.

5.2 Standby Power (Emergency Generator Set) System

The emergency power back up system adopted in the building isstandby generator set of 650kVA rating. The primer mover used isdiesel engine. The generator room is located at Basement Level 1,just next to the main switch room. This can reduce the capital costas the emergency power cables from generator to L.V. switchboard areshortened. Before the determination of adopting standby generator, we analyzethe diesel engine is automatically start up and the set can take upthe load within a time period of 15 seconds as stipulated in FSDrequirement.

One feature of this building design is that we has classified theessential supply into two categories as below:

Category 1: Services essential to the safety of human life and property; power supply to theseservices will be maintained for continuous operation for six hours in case of normal powerfailure.


Category 2: Services essential to continual operation of the building; essential power supplyto these services will be automatically cut-off in case of fire or low fuel level of generator setso as to maintain adequate fuel storage capacity for the genset to back up the operation ofabove category 1 service for operation for six hours in case of normal power failure.

The control logic is discussed later in special design consideration.

5.3 Lighting System

Power supply to lighting and equipment are supplied from differentMCB board located in various electrical riser ducts/switch rooms.

Lighting fixtures are well constructed and comply with therequirements of BS4533.

All fluorescent light fittings used are designed to be equipped withlow loss, high power factor electronic ballast in order to complywith the Green issue of energy saving concept. It is very commonlyuse in Hong Kong nowadays.

Outdoor luminaires are able to withstand outdoor weather conditionwith a minimum protection class of IP54.

Luminaires for gas-discharged lamp, such as fluorescent, mercuryvapour, sodium vapour etc., which utilizes choke as part of thecircuit are equipped with capacitor to ensure the overall powerfactor of the lighting circuit does not fall below 0.85.

Battery lights and EXIT signs are self-contained charge type withbuilt-in inverter and nickel-cadmium battery. The capacity ofbattery is able to light the lamp for a minimum of 2 hours atfunctional operation as stipulated under FSD requirement.

For energy saving, all fluorescent tubes used are of bi-pin energysaving 26mm in diameter type in compliance with BS1853 and a ratedlife of not less than 15,000 hours. The colour temperature of 4000Kand the colour rendering indexes of fluorescent tube shall not lessthan 80.

5.4 Earthing System

As to comply with CLP’s supply requirement and The Code of practicefor Electricity (wiring) Regulations, the consumer should provideits own earthing electrode system, we have to design an earthingsystem comprising earth electrode, earth conductors, circuitprotective conductors and equipotential bonding conductors insideour building.


All metal works associated with the electrical installation but notforming parts of a live conductor, including exposed conductiveparts and extraneous conductive parts, are solidly and effectivelybonded and earthed in accordance with the latest edition of BristishStandard BS7671:1992.

A solid tinned copper main earthing terminal is provided near themain incoming switch at Main Switch Room on theGround Level for theconnection of the earth cu. tape. The main equipotential bondingconductors and the earthing conductors to create the equipotentialzone.

The main earthing terminal is connected to earth via a 6x25mm tinnedcopper earth tape to an earth electrode or a group of electrodes.The overall earth loop impedance shall be less than 0.5 ohm forelectrical system.

The neutral point of the generator alternator is earthed by a 25x3mmpvc copper tape connected to the main electrical earth.

Individual earthing terminals are provided inside each telephonebroadcasting equipment (TBE) room, all plant rooms including fanrooms, lift machine rooms , electrical riser duct and pump roomsetc. They should also be required to bond together to the mainearthing terminal at main switch room by a 3x25mm copper tapeseparately.

As previously discussed in our design main theme that all theincoming cables, including water pipes, utility company’s power andtelephone cables designed into the building at one point and thenbonding these services to the main earthing terminal in the mainswitch room for surge protection.

5.5 Lightning Protection System

Although the building is not too high and is lower than thesurrounding buildings, we shall provide the lightning protectionsystem in this building for safety reasons.

The lightning protection system for the whole building comprisinghorizontal conductors at top and flat roof of the building and downconductors using separate re-bars embedded inside column at the timeof construction of the building.

By embedding re-bars (down conductors) inside concrete along thecolumn is time saving and almost maintenance free.


The protection system adopted using copper tape network on roofbonded to the individual and separate reinforcement bar of 10mm dia.(down conductors) run along column superstructure by thermalwelding. The lightning protection system is installed in accordancewith BS 6651. Each down conductor, at 10m interval apart, isconnected to an earth electrode at Basement Level 3.

Each of these earth terminations should have a resistance to earthnot exceeding 10 ohms.

Finally, the lightning protection systems should also bonded to themain earthing terminal at main switch room by a 3x25mm copper tapeto achieve the equipotential bonding.

5.6 Doorphone & Security System

The apartment blocks comprising doorphone security system for forpreventing unauthorized visitors from entering the apartment. Eachvisitor panel is equipped with CCTV Camera at entrance.

Digital visitor panels with integrated colour CCTV camera will beinstalled at the G/F and podium level entrances of each apartmentblock. All visitors can communicate through the visitor paneloutside the entrance. The camera signal and picture can be receivedand displayed at video doorphone handset station and at TV unitthrough CABD system.

The visitor panel has two way communication with any flat unitwithin the same apartment block by pressing the call button equippedon the entrance panel. On receiving the call from the visitor, theoccupant of the flat unit will use his videophone handset locatedinside the flat to communicate with the visitor. He can then releasethe electric lock of the entrance if the visitor is allowed to enterthe building.

An electronic combination lock system is designed for the use by theresident to enter the apartment without having to use keys.

A panic alarm button is installed in each master bedroom forsecurity purpose. The panic alarm signals from the panic alarmbutton and doorphone handset will be transmitted to the securitycontrol room.

When an alarm is reported to the alarm control panel, an audibletone sounds from security alarm panel to alert the operator that analarm is waiting to be processed. A visual indication will also beprovided to indicate the alarm point in the control panel.

University of Central LancashireBEng (Hons) Building Services EngineeringModule: BN3232 – System Design Design Report for Electrical Installation______________________________________________________________________________________5.7 CABD/SMATV/Cable TV System

The whole composite building are designed to install a CABD, SMATVand Cable TV System providing TV/FM and Satellite TV/ Cable TVBroadcasting facilities for all tenants including shops, officetenants and apartments flats.

The receiving end is installed for this development to receive thebroadcast of local TV/FM channels (JADE, PEARL, ATV-C and ATV-E,RTHK & CRHK) and channels from satellite. An UHF aerial and FMaerial are installed on the roof of the Office tower. It enablethat systems can receive the maximum signal level.

One satellite dish will also be installed at the roof of theBuilding and the signal will be fed to shops, office and apartmentflats for the whole composite building.

Signals are amplified through the pre-amplifier and are aligned bythe channel equalization amplification equipment. These alignedsignals are combined with the FM signals and Local TV signals. Theyare branched into each outlet through the use of splitter, tee unitand wide band distribution amplifiers.

Headend & Amplifier equipment are installed on 19/F electrical riserduct and is connected between the receiving aerials and theremainder of the CABDS to process the signals to be distributed.The headend comprise of channel amplifiers, distribution amplifiersand channel converters.

FM/TV Socket OutletOutlet is twin socket type for VHF and UHF signals complete withfrequency dividing network and the respective socket is identifiedwith labels embossed on the front plate.

5.8 CCTV Surveillance System

The Closed Circuit Television System (CCTV System) is an integralpart of the security systems. It is used to monitor strategicpositions inside the building including entrance, driveway, entrancehall, shopping arcade, external boundary and landscape area. Allcameras are equipped with the panning feature.

All lift cars are also equipped with CCTV camera for surveillanceand security purpose.

The system comprised CCTV cameras, multiplexer, monitors, and timelapse VCR. The panning control panel is resident at Control Room.


In addition, a permanent record of these pictures from all camerascan be stored and replayed by means of a 24 hours video taperecorder.

5.9 Public Address System

Public Address System is used to send messages through an audioequipment. This system makes addressing the public the easier way.

Each floor is installed with speakers which are connected to thepaging microphone, cassette player and CD player via the volumecontrol unit, zone selector and power amplifier at G/F managementoffice.

Public Address System is provided in the Main Lobbies, Toilets,Corridors and Shopping Arcade and etc. with different zones.

The paging microphone is used to inform the public of anyinformation.All P.A. equipments are designed be fed by essential supply.

The cassette player and CD player is used for playing backgroundmusic. When the operator uses the paging microphone or thecassette/CD player, the voice messages or music can be heard at theselected speaker. Recessed ceiling speakers are installed in false ceiling of shoparcade while wall mounted speakers are mounted at exhibition halls.

5.10 Telephone/Communication System

The telephone/communication system of the composite building isprovided by the Hong Kong Telecom Co. A TBE room is located in Ground Level for the incoming telephonecables termination and accommodation of telephone equipments.

6.0 Special Design Consideration


6.1 Presence Detectors for Office Lighting Control

Operation Principle

As the building envelop mainly consist of curtain wall. Daylight canbe easily come into the building and therefore very suitable to usein the open office in this building. A presence detector consists ofa passive infra-red detector with built-in photocell. The infra-reddetector is used to sense the presence of person whereas thephotocell is used to detect the daylight level from outside. Whendetection of the presence of occupant, with insufficient daylight,lights will turn on.

When detection of no occupant, no matter with sufficient orinsufficient daylight at that time, lights will never turn on untilthe detection of presence of occupant again. This lighting controlhighly reduces energy consumption as well as the maximum use ofnatural daylight.

Features

- Effective use in areas which are unoccupied for long periods oftime, e.g. store room and toilets.

- Isolate lightings for overtime working.

- Energy saving between 40%-60% can be expected.

- Ensures lights are always available for use but are not switchedon unless someone needs them.

- Hands free control covering a 7metre diameter area.

- Minimum ambient light level detection can be adjusted to ensureluminaires are switched on when required for the occupants

- Provide additional security by switching on if intruders are detected in an unoccupied office.

- Provide flexibility to incorporate an adjustable time delay before switching luminaires off.

8back up the operation of above category 1 service for operation for six hours in case ofnormal power failure. Therefore, the emergency load connected to the generator set in caseof fire or low fuel oil is sensed during generator running, it will


automatically cut some unnecessary loading, such as essential A/Cloads from MCC. By doing so, we can reduce the burden(load) of thegenerator.

The control logic is shown as follow:

Fire Signal(0=No signalreceived,

1=Fire signalreceived)

Low Fuel Level(0=No signal

received, 1=Lowfuel levelsignal

received)

Status ofTripping ACBfor Category 2

load.(0=ACB remainsclose, 1=Trip

ACB)0 0 00 1 11 0 11 1 1

7.0 Appendix

A Load AssessmentB Generator Set Size AssessmentC Calculation of Fuel Oil Tank SizeD Sample Cable Sizing CalculationE Calculation for Capacitor Bank Sizing AssessmentF Lightning Protection Design System and Lightning Risk

Assessment

University of Central LancashireBEng (Hons) Building Services EngineeringModule: BN3232 – System Design Design Report for Electrical Installation______________________________________________________________________________________8.0 Drawings

Drawing no. DescriptionEL-01 Schematic Diagram for Electrical InstallationSD/GBP/01 Ground Floor Layout PlanSD/GBP/02 First Floor Layout PlanSD/GBP/03 Second Floor Layout PlanSD/GBP/04 3/F~19/F Layout PlanSD/GBP/05 Roof Floor Layout Plan


9.0 Reference

10.1 Code of Practice for Energy Efficiency for Electrical Installation 1988

Edition

10.2 Code of Practice for the Electricity (Wiring) Regulations1997 Edition

10.3 General notes/hand outs for Electrical Services from Year 1 to3.

BN3232 Design report EE

Documents

Transcript of BN3232 Design report EE