usm_mechanical and electrical engineers in land development projects

1

By:

Muhammad Arkam Bin Che Munaaim, PhD, PEng, IntPE

PhD (Energy Conservation), USM; MSc. B Tech (Energy) (USM); B. Elec. Eng. (Hons) (UTM); Dip. Elec. Eng (Power) (UTM).

MIEM, MIET (UK), MIEEE (USA), ASEAN Eng, APEC Eng, EMF IntPE, Chartered Eng (ASEAN), AAE, SPAN QP, REEM, MWA, MySET.

HP: +6016 335 7727 Email: [email protected]

Mechanical and Electrical Systems in Building and Land Development Projects

Lecture Content - Part 1: M&E Engineers in Land Development(What Do We Do?)

• Initial (Concept -Tapping Design)• Application of “Planning Approval” from Authorities:• 1) Tenaga Nasional Berhad (TNB)• 2) Telekom Malaysia (TM) • 3) Malaysia Communication and Multimedia

Commission (MCMC)• Submission of above approval to the Lead Consultant• Lead Consultant to Local Authority (Council) for Development Order

(DO) Approval.• Concept Design Starts (Design Office)• Design Approval (From Client)• Letter Examples

Lecture Content - Part 2:

1) Design of Power Distribution System in Buildings 2) Basic Principles or Factor Requiring Consideration During Design3) Goals of System Design4) Low Voltage Distribution System (Principles)5) Selecting a Distribution Schemes6) Rules and Statutory Regulations7) Definitions of Voltage Ranges8) TNB Supply Schemes and Maximum Demand Level for Low Voltage System

ELECTRICAL INSTALLATION

DESIGN

Design of Power Distribution System in Buildings

The best distribution system is one that will, cost effectively and safely, supply adequate electric service to both present and future probable loads

Function of the electric power distribution systemTo receive power at one or more supply points and deliver it to the individual lamps, motors, and all other electrically operated devices.


DESIGN

Basic Principles or Factor Requiring Consideration During Design

• Functions of structure, present and future.

• Life and flexibility of structure.• Locations of service entrance and

distribution equipment, locations and characteristics of loads, locations of unit substations.

• Demand and diversity factors of loads.

• Sources of power; including normal, standby and emergency.

• Continuity and quality of power available and required.

• Energy efficiency and management.• Distribution and utilization voltages.• Bus and/or cable feeders.• Distribution equipment and motor

control.• Power and lighting distribution

boards and motor control centers.• Types of lighting systems.• Installation methods.• Power monitoring systems.• Electric utility requirements.


DESIGNGoals of System Design

1) SafetyTo design the power system which will not present any electrical hazard to the people who utilize the facility, and/or the utilization equipment fed from the electrical system

2) Minimum Initial InvestmentThe owner’s overall budget for first cost purchase and installation of the electrical distribution system and electrical utilization equipment will be a key factor in determining which of various alternate system designs are to be selected. When trying to minimize initial investment for electrical equipment, consideration should be given to the cost of installation, floor space requirements and possible extra cooling requirements as well as the initial purchase price


DESIGNGoals of System Design (Cont…)

3) Maximum Service ContinuityThe degree of service continuity and reliability needed will vary depending on the type and use of the facility as well as the loads or process being supplied by the electrical distribution system.

Typically, service continuity and reliability can be increased by:

Supplying multiple utility power sources or services

Supplying multiple connection paths to loads served

Using short time rated power circuit breakers Providing alternate customers owned power

sources such as generators or batteries supplying uninterruptible power supplies

Selecting the highest quality electrical equipment and conductors

Using the best installation methods Designing appropriate systems alarms,

monitoring and diagnostics Selecting preventative maintenance systems or

equipment to alarm before an outage occurs



4) Maximum Flexibility & ExpendabilityIn many industrial manufacturing plants, electrical utilization loads are periodically relocated or changed requiring changes in the electrical distribution system. Consideration of the layout and design of the electrical distribution system to accommodate these changes must be considered

5) Maximum Electrical Efficiency (Minimum Operating Costs)Electrical efficiency can generally be maximized by designing systems that minimize the losses in conductors, transformers and utilization equipment. Proper voltage level selection plays a key factor in this area and will be discussed later. Selecting equipment, such as transformers, with lower operating losses, generally means higher first cost and increased floor space requirements; thus, there is a balance to be considered between the owner’s utility energy change for the losses in the transformer or other equipment versus the owner’s first cost budget and cost of money.



6) Minimum Maintenance CostUsually the simpler the electrical system design and the simpler the electrical equipment, the less the associated maintenance costs and operator errors. As electrical systems and equipment become more complicated to provide greater service continuity or flexibility, the maintenance costs and chance for operator error increases. The systems should be designed with an alternate power circuit to take electrical equipment (requiring periodic maintenance) out of service without dropping essential loads. Use of drawout type protective devices such as breakers and combination starters can also minimize maintenance cost and out-of-service time.

7) Maximum Power QualityThe power input requirements of all utilization equipment has to be considered including the acceptable operating range of the equipment and the electrical distribution system has to be designed to meet these needs


DESIGN

Low Voltage Distribution System (Principles)

MSB

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S S B 2

S S B 3

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• Distribution from the Main Switchboard (MSB)

• At this level, power from one or more MV/LV transformers connected to the MV network of the electrical utility is distributed to:- Different areas of the sites: shops in a factory, homogeneous production areas in industrial premises, floor in the office buildings, etc.- Centralised high power loads such as air compressors and water cooling units in industrial processes or air conditioners and lifts in office buildings.

• Sub distribution used to distribute electricity within each area

• Final distribution, used to supply the various loads


DESIGN

Low Voltage Distribution System (Principles)

Basic TopologiesAll distribution systems are combinations of two basic

topologies:1. Star topologies: Radial or centralized distribution2. Bus topologies: Distribution using busduct / busways

(also referred to as busbar trunking system)

Star Topologies

Bus Topologies


DESIGNSelecting a Distribution Schemes

The LV distribution scheme is selected according to:• Energy availability requirements

The criterion of independent circuits to different parts of an installation makes it possible to:

1. Limit the consequences of a fault to the circuit concerned

2. Simply fault locating3. Carry out maintenance work or circuit extensions

without interrupting the supply of power to the whole installation.

• Size of the site (area & total power to be distributed)Small sites are supplied directly by the utility’s LV network and the size and power requirements of the installation do not justify a three level distribution system. Electrical distribution in all premises (stores, homes, small offices) most often involves only one or two levels.


DESIGNSelecting a Distribution Schemes

• Load layout (equipment and power density)Two types of loads, depending on their layout on the site, must be taken in account:

• Concentrated load, generally corresponding to building utilities used for the entire site and requiring high power (e.g. centralized air conditioning units, lifts, refrigeration units in supermarket)

• Distributed loads that can be dealt with in groups corresponding to a homogeneous area (floor, factory shop, production line) and characterized by two parameters: power density (in VA/m2) and equipment density (in number of devices per 10 or 100m2)

• Installation flexibility requirementsInstallation flexibility is an increasingly important requirement, in particular for commercial and industrial premises.


DESIGNRules and Statutory Regulations

Low-voltage installations are governed by a number of regulatory and advisory texts, which may be classified as follows:

1. Statutory regulations (decrees, factory acts, etc.),2. Codes of practice, regulations issued by professional

institutions, job specifications,3. National and international standards for installations,4. National and international standards for products.

The electricity supply and installation practice in Peninsular Malaysia are governed by the following:

1. Electricity Supply Act 1990 – Act 4472. Licensee Supply Regulation 19903. Electricity Regulation 19944. OSHA 1994 – Occupational, Safety & Health Act5. Malaysia Standard MS IEC 60364 Electrical Installation of

Buildings6. The current edition of the IEE Wiring Regulations for

Electrical Installations, where necessary (IEE Wiring Regulation 16th Edition)

7. Electricity Supply (Successor Company) Act 1990 – Act 448


DESIGN

TNB Supply Schemes and Maximum Demand Level for Low Voltage

System

MD Ranges of Individual Customer

Supply Voltage

Typical Supply Scheme

Up to 12kVA 415V • Overhead services from LV mains

12kVA to 100kVA 415V • Three phase overhead or underground cable service from existing LV mains

100kVA to 1000kVA 415V • Direct cable services from LV board from a substation

Typical supply schemes for various Maximum Demand (MD) levels


DESIGN

No Type of Premises Minimum

(kW)

Average

(kW)

Maximum

(kW)

1 Low cost flats, single storey

terrace

1.5 2.0 3.0

2 Double storey terrace or apartment

3.0 4.0 5.0

3 Single storey, semidetached

3.0 5.0 7.0

4 Single storey bungalow & three room condominium

5.0 7.0 10.0

5 Double storey bungalow &

luxury condominium

8.0 12.0 15.0

Range of Maximum Demand (MD) for domestic customer subclasses or premises


System


DESIGN

Range of Maximum Demand (MD) for types of shop houses


System

No Type of Premises Minimum

(kW)

Average

(kW)

Maximum

(kW)

1 Single storey, semidetached

5 10 15

2 Double storey shop house

15 20 25

3 Three storey shop house 20 30 354 Four storey shop house 25 35 455 Five storey shop house 30 40 55


DESIGNRules and Statutory Regulations

Types of supply applications are provided by TNB can be classified into three types:• Supply application for load up to 100kVA

Supply usually from existing supply mains Submission of applications to TNBD by Electrical

Contractor registered with Suruhanjaya Tenaga (ST)

Processing period for supply will take a maximum of 3 weeks upon approval from the local authorities.

• Supply application for load exceeding 100kVA Supply may require establishment of new

substation Submission of applications to TNBD by Consultant

Engineer Processing period for supply may take between 6

months to 3 years depending on the extent of electrical infrastructure required.

• Supply application for streetlight Application made by the local

authority/government department Application by developer Application by individual


1) Definition of a final circuit2) Final Circuit Distribution3) Final circuit feeding 13A sockets to BS 1363 4) Radial circuit arrangement 5) Ring circuit arrangement6) Diversity Factor7) Maximum Demand

Definition of a final circuit

• A circuit connected directly to current using equipment, or to a socket outlet or socket outlets or other points for the connection of such equipment

• An outlet is defined as the termination of fixed wiring feeding a luminaire, socket, or any current consuming appliance. From this it will be seen that a final circuit might consist of a pair of 1.5mm2 cables feeding a few lights or a very 3 core cable feeding a large motor direct from a circuit breaker or main switchboard.

• Socket outlet: A device, provided with female contacts, which is intended to be installed with the fixed wiring, and intended to a receive plug. A luminaire track system is not regarded as a socket outlet system

Definition of a final circuit

Final Circuit Distribution

• Final circuits can be divided into the following types, all of which will need different treatment when planning the size of the conductors and the rating of the overcurrent devices:The general of final circuits are:

1. Final circuit feeding fixed equipment or 2A sockets.2. Final circuit feeding 13A sockets to BS 13633. Final circuit feeding sockets to BS 196 (5A, 15A, and

30A)4. Final circuit feeding sockets to BS EN 60309-2 (industrial

types 16A, 32A, 63A and 125A)5. Final circuit feeding fluorescent or types of discharge

lighting6. Final circuit feeding motors7. Final circuit feeding cookers

Sockets

Final circuit feeding 13A sockets to BS 1363

• The main advantages of the 13A socket with fused plug are that any appliance with a loading not exceeding 3.12kW (13A at 240V) may be connected with perfect safety to any 13A socket, and under certain conditions an unlimited number of socket may be connected to any one circuit

• One point which must be borne in mind by the designer is the question of the use of

outdoor equipment. • 13A socket outlets circuits can be fed by

either radial or ring circuits.

Final circuit feeding 13A sockets to BS 1363(Radial circuit arrangement)

Final circuit feeding 13A sockets to BS 1363(Ring circuit arrangement)

• A ring circuits utilises one additional conductor to loop back to the sending end. In other words, the socket outlets in the ring circuit are fed by two parallel conductors.

• The sharing of the load between the two parallel conductors will depend on the load distribution within the ring.

Malaysia Practices for 13A Socket Outlet (BS 1363)

Types of 13A Socket Outlets

Area Malaysia Practices

Size of wires Fuse/Circuit Breaker Rating

1. Single socket outlet 20m2 • 2.5mm2 PVC cables

16A

2. Double socket outlet 20m2 • 2.5mm2 PVC cables

20A

3. Ring (10 Nos 13A socket outlet provided they are all located within an area of not more than 1000 sq feet)

100m2 • 2.5mm2 PVC cables

32A

4. Radial (Max 6 Socket Outlets)

50m2 • 4mm2 PVC cables

32A

• Diversity factor, DF is the ratio of the sum of the maximum power demands of the subdivisions, parts of a system, to the maximum demand of the whole system or part of the system under consideration.

Diversity Factor

• Maximum demand (often referred to as MD) is the largest current normally carried by circuits, switches and protective devices; it does not include the levels of current flowing under overload or short circuit conditions- Example of Electric Circuit.

Maximum Demand

(DF)Factor Diversity x CL Load MD Demand, ConnectedMaximum


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