1. Electrical Equipment A) Transformer

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Standards and Basic Equipment

Date : 15 November 2010

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

1. Electrical Equipment

2 Terminology

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2. Terminology

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1. Electrical Equipment

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A1) One Transformer and 11kV

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B ildi

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Switchgear in High Rise Building

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A2) Three Transformers and 11kV

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B ildi

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B ildi

Switchgear in High Rise Building

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A3) Minimum Requirements for the Customer’s Switchroom

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Adjacent to Substation for Multi

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E) MCCB

D) Fuses Combination Unit (Switch Fuse)( )

B) Switch Board C) ACB

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1. Electrical Equipment

B) F t

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Typical forms of separation by

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barriers of partition

Form 1

Form 1 No separation

No separation

Form 2

Form 2 Separation of busbar from the functional

Separation of busbar from the functional

Form 2

Form 2 Separation of busbar from the functional

Separation of busbar from the functional

units

Form 3

Form 3 Separation of busbar from the functional

Separation of busbar from the functional

units and separation of all functional units

but not of their outgoing terminals, from one

another

another.

Form 4

Form 4 Separation of busbar from the functional

Separation of busbar from the functional

units and separation of all functional units,

including their outgoing terminals, from one

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,

another.

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1. Electrical Equipment

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C) Air Circuit Breakers (ACB)

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1. Electrical Equipment

D) F

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D) F

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

D) Fuse Combination Units and Switch

D) Fuse Combination Units and

Switch--disconnections

disconnections

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1. Electrical Equipment

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E) Moulded Case Circuit Breakers (MCCB)

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H) MCB F) Busbar Riser I) KWH Meter F) Busbar Riser G) MCB Distribution G) MCB Distribution Board

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1 1 Electrical Eq ipment

Electrical Eq ipment

1 1. Electrical Equipment

. Electrical Equipment



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1. Electrical Equipment

G) MCB Di t ib ti

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G) MCB Di t ib ti

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1. Electrical Equipment

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H) Miniature Circuit Breakers (MCB)

H) Miniature Circuit Breakers (MCB) 11

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1. Electrical Equipment

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H) Miniature Circuit Breakers (MCB)

H) Miniature Circuit Breakers (MCB) 22

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1. Electrical Equipment

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I) KWH meter

 

I) KWH meter

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L) Lighting Switch M) Lampholder N) Socket Outlet K) RCCB O) Connection Unit J) Consumer Unit

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1. Electrical Equipment

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J) C

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1. Electrical Equipment

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K) Residual Current Circuit Breakers (RCCB)

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1. Electrical Equipment

L) Li hti

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L) Li hti

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1. Electrical Equipment

M) L

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M) L

h ld

 

M) Lampholders

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1. Electrical Equipment

N) S k t

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N) S k t

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1. Electrical Equipment

O) C

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O) C

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1. Electrical Equipment

P) PVC C bl

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P) PVC Cable

P) PVC Cable -- 11

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1. Electrical Equipment

P) PVC C bl

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P) PVC Cable

P) PVC Cable -- 22

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1

1 2. Terminology

2. Terminology -- 1

1

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Live Part

A conductor or conductive part intended to be A conductor or conductive part intended to be



 A conductor or conductive part intended to be A conductor or conductive part intended to be

energized in normal use, including a neutral energized in normal use, including a neutral conductor

conductor conductor. conductor.



Electrical Installation



 An assembly of associated electrical equipment An assembly of associated electrical equipment

supplied from a common origin to fulfill a specific supplied from a common origin to fulfill a specific purpose and having certain coordinated

purpose and having certain coordinated characteristics.

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2 2. Terminology

2. Terminology -- 2

2

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Electrical Equipment

Any item for such purposes as generation conversion Any item for such purposes as generation conversion



 Any item for such purposes as generation, conversion, Any item for such purposes as generation, conversion,

transmission, distribution or utilization of electrical transmission, distribution or utilization of electrical energy such as machines transformers protective energy such as machines transformers protective energy, such as machines, transformers, protective energy, such as machines, transformers, protective devices, wiring materials, measuring instruments, devices, wiring materials, measuring instruments, accessories appliances and luminaries

accessories appliances and luminaries accessories, appliances and luminaries. accessories, appliances and luminaries.



Fixed Appliance



 An appliance which is fastened to a support or An appliance which is fastened to a support or

otherwise secured at a specific location in normal use. otherwise secured at a specific location in normal use.

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3 2. Terminology

2. Terminology -- 3

3

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Portable Appliance

pp



 An appliance which is or can easily be moved from An appliance which is or can easily be moved from

one place to another when in normal use and while one place to another when in normal use and while pp connected to the supply.

connected to the supply.



Earthing



 The act of connecting the exposed conductive parts The act of connecting the exposed conductive parts

of an installation to an earth electrode. of an installation to an earth electrode.

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4 2. Terminology

2. Terminology -- 4

4

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Protective Conductor



 A conductor used for some measure of protection A conductor used for some measure of protection

against electric shock and intended for connecting against electric shock and intended for connecting gg gg together any of the following parts:

together any of the following parts:



 Exposed conductive parts,Exposed conductive parts, 

 Extraneous conductive parts,Extraneous conductive parts,

Main

Main earthingearthing terminalterminal



 Main Main earthingearthing terminal,terminal, 

 Earth electrodesEarth electrodes 

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5 2. Terminology

2. Terminology -- 5

5

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Equipotential

Equipotential Bonding

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Bonding

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

 Electrical connection maintaining various exposed Electrical connection maintaining various exposed

conductive pats and extraneous conductive parts at conductive pats and extraneous conductive parts at pp pp substantially the same potential

substantially the same potential



Exposed Conductive Part



 A conductive part of equipment which can be touched A conductive part of equipment which can be touched

and which is not a live part but which may become and which is not a live part but which may become live under fault conditions

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6 2. Terminology

2. Terminology -- 6

6

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Extraneous Conductive Part



 A conductive part liable to introduce a potential, A conductive part liable to introduce a potential,

generally earth potential, and not forming part of the generally earth potential, and not forming part of the

g y p , g p

electrical installation. electrical installation.



Circuit Protective Conductor (CPC)

A i d i d



 A protective conductor connecting exposed A protective conductor connecting exposed

conductive parts of equipment to the main

conductive parts of equipment to the main earthingearthing

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terminal. terminal.

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7

7 2. Terminology

2. Terminology -- 7

7

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Earthing

Earthing Conductor

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Conductor



 A protective conductor connecting a main A protective conductor connecting a main eathingeathing

terminal of an installation to an earth electrode or to terminal of an installation to an earth electrode or to other means of

other means of earthingearthing..



Direct Contact

C f li k i h li hi h



 Contact of persons or livestock with live parts which Contact of persons or livestock with live parts which

may result in electric shock. may result in electric shock.

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8 2. Terminology

2. Terminology -- 8

8

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Indirect Contact



 Contact of persons or livestock with exposed Contact of persons or livestock with exposed

conductive parts made live by a fault and which may conductive parts made live by a fault and which may pp yy yy result in electric shock.

result in electric shock.



Skilled Person

A i h h i l k l d ffi i



 A person with technical knowledge or sufficient A person with technical knowledge or sufficient

experience to enable him to avoid danger which experience to enable him to avoid danger which

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electricity ay create. electricity ay create.

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9 2. Terminology

2. Terminology -- 9

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Instructed Person

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 A person adequately advised or supervised by skilled A person adequately advised or supervised by skilled

persons to enable him to avoid dangers which persons to enable him to avoid dangers which

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electricity may create. electricity may create.



Low Voltage (L.V.)

V l ll di E L V l b



 Voltage normally exceeding Extra Low Voltage but not Voltage normally exceeding Extra Low Voltage but not

exceeding 1000V

exceeding 1000V a.ca.c. or 1500 . or 1500 d.cd.c. between . between

d t 600V

d t 600V 900V900V dd b tb t

conductors, or 600V

conductors, or 600V a.ca.c. or 900V . or 900V d.cd.c. between . between conductors and earth.

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10 2. Terminology

2. Terminology -- 10

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Extra Low Voltage

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 Voltage normally not exceeding 50V Voltage normally not exceeding 50V a.ca.c. or 120 . or 120 d.cd.c., .,

whether between conductors or to earth. whether between conductors or to earth.

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3. Power Distribution and Wiring

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Design Consideration

Design Consideration -- 1

1

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Installation Cost



Purpose and planned duration of the installation



Purpose and planned duration of the installation



Environment factors and installation conditions



Type of building construction



Flexibility of the system and circuit arrangement



Flexibility of the system and circuit arrangement



Appearance of the finished installation

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

Safety aspect



Nature of power supply and type of earthing

system

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3 3 1

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3 3..1

1 Installation at High Humidity

Installation at High Humidity

Environment



 The wiring system should be selected and erected so The wiring system should be selected and erected so

that no damage is caused by high humidity or ingress of that no damage is caused by high humidity or ingress of

Environment

g y g y g

water during installation, use and maintenance. water during installation, use and maintenance.



 All joint should be suitably insulated and protected All joint should be suitably insulated and protected

against the effects of moisture or water. Copperclad against the effects of moisture or water. Copperclad aluminum conductors should not be used.

aluminum conductors should not be used.

f h d d k h ld b



 Every entry to finished ducts or trunking should be Every entry to finished ducts or trunking should be

placed so as to prevent the ingress of water or be placed so as to prevent the ingress of water or be

protected against such ingress Where water may collect protected against such ingress Where water may collect protected against such ingress. Where water may collect protected against such ingress. Where water may collect or condensation may form in a wiring system, provisions or condensation may form in a wiring system, provisions should be made to drain it away.

should be made to drain it away. should be made to drain it away. should be made to drain it away.

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3.1 Installation at Adverse Ambient

Temperature



 The wiring system including cables and wiring The wiring system including cables and wiring

accessories, should be suitable for the highest and lowest accessories, should be suitable for the highest and lowest accessories, should be suitable for the highest and lowest accessories, should be suitable for the highest and lowest ambient temperature that likely to encountered.

ambient temperature that likely to encountered.



 The electrical insulation shall withstand the maximumThe electrical insulation shall withstand the maximum 

 The electrical insulation shall withstand the maximum The electrical insulation shall withstand the maximum

permissible operating temperature of the class of permissible operating temperature of the class of insulation to BS 2757 insulation to BS 2757 insulation to BS 2757. insulation to BS 2757. Class Class YY AA EE BB FF HH 200200 220220 250250 Temp( Temp(oo_C)_{C) 90}₉₀ ₁₀₅_{105 120}_{120 130}_{130 155}_{155 180}₁₈₀ ₂₀₀₂₀₀ ₂₂₀₂₂₀ ₂₅₀₂₅₀

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3.1 Installation at Adverse Ambient

Temperature

Temperature -- 2

2



For general

For general--purpose PVC cable, the

purpose PVC cable, the

maximum permissible conductor of

operating temperature is 70

oo

_{C and the}

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bi t

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bi t

maximum permissible ambient

temperature is 65

_pp

oo

_C.



In every vertical

In every vertical trunking

trunking or duct wiring

or duct wiring

installations suitable internal barriers

installations, suitable internal barriers

sould

sould be provided between floors or at

be provided between floors or at

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f 5

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intervals of 5m whichever is the less.

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3.1 Installation at Adverse Ambient

Temperature

Temperature -- 3

3



Suitable measures shall be provided to

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avoid the effects of heat from external

source including solar gain such as

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shielding or placing sufficiently far from

the source of heat or selecting insulation

suitable for those temperature.

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3 1 Inde of Protection

3.1 Index of Protection



The code that specifies the protection of

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b

d ithi

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b

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encloses that can be used within certain

environment. The first numeral indicate

the protection against ingress of solid

bodies The second number indicate the

bodies. The second number indicate the

protection against the ingress of liquids.

p

g

q

p

g

q

IP XX

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3 1 Inde of Protection

3.1 Index of Protection



General Use



Indoor Use: IP2X



Outdoor Use: IP54 (Weather

Outdoor Use: IP54 (Weather--proof)

proof)



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3.1 Application of Wiring

pp

g

System

Wiring System

Wiring System Cable TypeCable Type General UseGeneral Use Surface wiring

Surface wiring 1/C PVC/PVC cables with 1/C PVC/PVC cables with Temporary wiring;Temporary wiring; separate cpc; separate cpc; 2/C PVC/PVC cables with 2/C PVC/PVC cables with cpc; cpc; Low

Low--cost housingcost housing 4/C armored cables 4/C armored cables Conduit wiring Conduit wiring 11 ConcealedConcealed 1/C PVC insulated cables

1/C PVC insulated cables Office,Office,

Private hosing; Private hosing; 1. 1. ConcealedConcealed 2. 2. SurfaceSurface Private hosing; Private hosing; Factory; Factory; Plant room Plant room Wiring in trunking

Wiring in trunking 1/C PVC insulated cables1/C PVC insulated cables SubSub--main/laternal main main/laternal main distribution

distribution Risers in communal

Risers in communal Bare Cu/Al bars in trunkingBare Cu/Al bars in trunking Rising mains for internalRising mains for internal Risers in communal

Risers in communal installation

installation Bare Cu/Al bars in trunkingBare Cu/Al bars in trunking_{Armored cables in cable}_{Armored cables in cable} duct

duct

Rising mains for internal Rising mains for internal power distribution system power distribution system Flameproof cable

Flameproof cable MineralMineral--insulated cablesinsulated cables Petrol station,Petrol station, Flammable areas Flammable areas

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3.2 Typical Schematic Wiring Diagram for Internal

Power Distribution System

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3.2 Internal Power Distribution

System



a) Basic Requirements



b) High Voltage Distribution

c) Mains



c) Mains



d) Sub

d) Sub -- Main

d) Sub

Main

aa



e) Lateral Main



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3.2 Internal Power Distribution

System



a) Basic Requirements

a) Basic Requirements 11

E i t ll ti h ll b di id d i t i it t E i t ll ti h ll b di id d i t i it t



 Every installation shall be divided into circuits as necessary to Every installation shall be divided into circuits as necessary to

avoid danger in the event of a fault, and to facilitate safe avoid danger in the event of a fault, and to facilitate safe operation, inspection, testing and maintenance. Each circuit operation, inspection, testing and maintenance. Each circuit operation, inspection, testing and maintenance. Each circuit operation, inspection, testing and maintenance. Each circuit should be separately protected by an

should be separately protected by an overcurrentovercurrent protective protective device. Separate circuits shall be provided for parts of the device. Separate circuits shall be provided for parts of the i t ll ti hi h d t b t l t ll d i h i t ll ti hi h d t b t l t ll d i h

installation which need to be separately controlled in such a way installation which need to be separately controlled in such a way that these circuits are not affected by failure of other circuits.

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3.2 Internal Power Distribution

System



a) Basic Requirements 2

P t ti d i f h i it h ld b l l

P t ti d i f h i it h ld b l l l b ll dl b ll d



 Protective devices of each circuit should be clearly Protective devices of each circuit should be clearly labelledlabelled or or

identified so that the rating of the devices and circuits they identified so that the rating of the devices and circuits they protect can be easily recognized.

protect can be easily recognized. protect can be easily recognized. protect can be easily recognized.

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3.2 Internal Power Distribution

System

B) High Voltage Distribution B) High Voltage Distribution--11



 Although residential and the majority of commercial installations are Although residential and the majority of commercial installations are

adequately served from LV

adequately served from LV intake or HVintake or HV intakeintake LV distribution thereLV distribution there adequately served from LV

adequately served from LV--intake or HVintake or HV--intakeintake--LV distribution, there LV distribution, there are many industrial and some large commercial development

are many industrial and some large commercial development projects require HV intake with extensive HV distribution system projects require HV intake with extensive HV distribution system through the sites or buildings

through the sites or buildings through the sites or buildings. through the sites or buildings.



 For example, a hospital or an university with a large campus, a For example, a hospital or an university with a large campus, a

cross harbor tunnel with high

cross harbor tunnel with high--tension motors for ventilation fans, a tension motors for ventilation fans, a very ;large commercial block and a large factory with several

very ;large commercial block and a large factory with several very ;large commercial block and a large factory with several very ;large commercial block and a large factory with several electrode boilers.

electrode boilers.



 For these, the power company provides the main supply point For these, the power company provides the main supply point

through its own switchgear complete with bulk metering and the through its own switchgear complete with bulk metering and the through its own switchgear complete with bulk metering, and the through its own switchgear complete with bulk metering, and the customer is then responsible for the installation of suitable high customer is then responsible for the installation of suitable high voltage switchgear, all cabling and the required number of on

voltage switchgear, all cabling and the required number of on--site site substations

substations substations. substations.

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3.2 Internal Power Distribution

System

B) HV Ring Main Distribution system B) HV Ring Main Distribution system



 Just similar to the ring main system which used by power company Just similar to the ring main system which used by power company gg yy y py p p yp y

in their 11kV network in their 11kV network

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3.2 Internal Power Distribution

System

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3.2 Internal Power Distribution

System

B) Advantage of HV Ring Main Distribution system B) Advantage of HV Ring Main Distribution system



 Even in the event of a cable fault on the ring, it is still possible to Even in the event of a cable fault on the ring, it is still possible to

maintain or restore supply to all points by opening the switches on maintain or restore supply to all points by opening the switches on both sides of the fault.

both sides of the fault.



 Additional outlets to the ring may be easily installed without shutAdditional outlets to the ring may be easily installed without shut 

 Additional outlets to the ring may be easily installed without shut Additional outlets to the ring may be easily installed without shut

downs. downs.



 Greater maintenance facilities are available both on the ring feeder Greater maintenance facilities are available both on the ring feeder

i it b k d th RMU i it b k d th RMU circuit breakers and the RMUs. circuit breakers and the RMUs.



 In additional, if the main HV switchboard is sectionalized and fed In additional, if the main HV switchboard is sectionalized and fed

from more than one supplier

from more than one supplier’’s substations, a ring main may bes substations, a ring main may be

from more than one supplier

from more than one supplier s substations, a ring main may be s substations, a ring main may be supplied from two different sections, thus improving security. supplied from two different sections, thus improving security.



 Apart from fault conditions, it is also possible to operate a ring main Apart from fault conditions, it is also possible to operate a ring main

in open mode as the preferred arrangement but for whatever in open mode as the preferred arrangement but for whatever in open mode as the preferred arrangement but, for whatever in open mode as the preferred arrangement but, for whatever

purpose it must be ensured that neither of the section is overload. purpose it must be ensured that neither of the section is overload.

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3.2 Internal Power Distribution

System



c) Mains

c) Mains -- 11

Consumer main switch shall be installed and Consumer main switch shall be installed and



 Consumer main switch shall be installed and Consumer main switch shall be installed and

connected immediately before the supply co.

connected immediately before the supply co.’’s meter.s meter.

A i it h h ll b i t ll d t t l ll



 A common main switch shall be installed to control all A common main switch shall be installed to control all

the communal installation of the same consumer. the communal installation of the same consumer.



 The consumer main switch should incorporate:The consumer main switch should incorporate:



 Means of isolation and switchingMeans of isolation and switching 

 Means of protection against Means of protection against overcurrentovercurrent, and , and 

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3.2 Internal Power Distribution

System



c) Mains

c) Mains -- 22

The main switch or circuit breaker shall have a short The main switch or circuit breaker shall have a short



 The main switch or circuit breaker shall have a shortThe main switch or circuit breaker shall have a

short--circuit breaking capacity of 40kA at low voltage. circuit breaking capacity of 40kA at low voltage.

Th h t i ti f th i it h h ll di t



 The characteristic of the main switch shall disconnect The characteristic of the main switch shall disconnect

within 5 seconds during an earth fault. within 5 seconds during an earth fault.



 The switchboard shall incorporate The switchboard shall incorporate CastellCastell key key

interlock or other means to prevent the supply interlock or other means to prevent the supply

f d i ll l All i i

transformers operated in parallel. All interconnecting transformers operated in parallel. All interconnecting devices including the bus

devices including the bus--section switch shall be of 4section switch shall be of

4--l t ith l t i l d h i l i t l k

l t ith l t i l d h i l i t l k

pole type with electrical and mechanical interlock. pole type with electrical and mechanical interlock.

(59)

3.2 Internal Power Distribution

System



c) Mains

c) Mains -- 33

Where standby generator is installed mechanically Where standby generator is installed mechanically



 Where standby generator is installed, mechanically Where standby generator is installed, mechanically

interlocked

interlocked 44--pole changeover device shall be used pole changeover device shall be used for interconnection between the normal and standby for interconnection between the normal and standby for interconnection between the normal and standby for interconnection between the normal and standby source. A local switch shall be installed after a

source. A local switch shall be installed after a changeover device

changeover device changeover device. changeover device.



 Single phase consumer main switch shall be of double Single phase consumer main switch shall be of double

pole type pole type pole type. pole type.



 A schematic wiring diagram showing the main A schematic wiring diagram showing the main

di t ib ti t h ld b di l d th i

distribution system should be displayed near the main distribution system should be displayed near the main switch with rating

(60)

3.2 Internal Power Distribution

System



c) Mains

c) Mains -- 44



 Each consumer installation shall provided his ownEach consumer installation shall provided his own 

 Each consumer installation shall provided his own Each consumer installation shall provided his own

earthing

earthing systemsystem



 For 3 phase installation with main switch rating ofFor 3 phase installation with main switch rating of 

 For 3 phase installation with main switch rating of For 3 phase installation with main switch rating of

160A and above, C.T. operated meter shall be 160A and above, C.T. operated meter shall be installed.

installed.



 Warning Notice: Warning Notice: ‘‘DANGERDANGER--ELECTRICITY, ELECTRICITY,

UNAUTHORISED ENTRY PROHIBITED

UNAUTHORISED ENTRY PROHIBITED’’ with Chinese with Chinese

translation shall be painted or engraved on plastic translation shall be painted or engraved on plastic boards permanently fixed outside the door of

boards permanently fixed outside the door of switchrooms

switchrooms Each character shall not less thanEach character shall not less than switchrooms

switchrooms. Each character shall not less than . Each character shall not less than 50mm high.

(61)

3.2 Internal Power Distribution

System



c) Mains

c) Mains -- 55



The mina

The mina earthing

earthing terminal of the installation

terminal of the installation

should be bonded by a conductor of not less

yy

than 150mm

2 2

_copper

_{copper to the electricity}

_{to the electricity}

supplier’s transformer earth or metallic

supplier s transformer earth or metallic

sheaths of service cable.

(62)

3.2 Internal Power Distribution

System

c) LV Distribution c) LV Distribution--11



 LV distribution exist in nearly all electrical installations.LV distribution exist in nearly all electrical installations. 

 Nearly all LV distribution are in radial from.Nearly all LV distribution are in radial from. 

 The greater the impedance of the cable from the secondary of the The greater the impedance of the cable from the secondary of the

transformer to the LV switchboard the less be the potential transformer to the LV switchboard the less be the potential transformer to the LV switchboard, the less be the potential transformer to the LV switchboard, the less be the potential short

short--circuit current, and therefore these cables should not be circuit current, and therefore these cables should not be larger than necessary.

larger than necessary.



 If two 1500kVA transformer were connected in parallel, then the If two 1500kVA transformer were connected in parallel, then the

potential fault current could be as much as 60MVA. As this potential fault current could be as much as 60MVA. As this

exceeds the breaking capacity of most standard LV switchboards exceeds the breaking capacity of most standard LV switchboards exceeds the breaking capacity of most standard LV switchboards exceeds the breaking capacity of most standard LV switchboards ( which is usually only 31 MVA, it would entail the installation of ( which is usually only 31 MVA, it would entail the installation of much more expensive switchboard or special high

much more expensive switchboard or special high--reactance reactance

transformers or split the LV main switchboards into two or more transformers or split the LV main switchboards into two or more transformers, or split the LV main switchboards into two or more transformers, or split the LV main switchboards into two or more separate sections, each section being fed from a transformer not separate sections, each section being fed from a transformer not exceeding 1500kVA.

(63)

3.2 Internal Power Distribution

System



 The greater the impedance of the cable from the secondary of the The greater the impedance of the cable from the secondary of the gg pp yy

transformer to the LV switchboard, the less be the potential transformer to the LV switchboard, the less be the potential short

short--circuit current, and therefore these cables should not be circuit current, and therefore these cables should not be larger than necessary

larger than necessary larger than necessary. larger than necessary.



 If two 1500kVA transformer were connected in parallel, then the If two 1500kVA transformer were connected in parallel, then the

potential fault current could be as much as 60MVA As this potential fault current could be as much as 60MVA As this potential fault current could be as much as 60MVA. As this potential fault current could be as much as 60MVA. As this

exceeds the breaking capacity of most standard LV switchboards exceeds the breaking capacity of most standard LV switchboards ( which is usually only 31 MVA, it would entail the installation of ( which is usually only 31 MVA, it would entail the installation of much more expensive switchboard or special high

much more expensive switchboard or special high--reactance reactance

transformers, or split the LV main switchboards into two or more transformers, or split the LV main switchboards into two or more separate sections each section being fed from a transformer not separate sections each section being fed from a transformer not separate sections, each section being fed from a transformer not separate sections, each section being fed from a transformer not exceeding 1500kVA.

(64)

3.2 Internal Power Distribution

System



 If If sectionisedsectionised is used in switchboard interlocked busis used in switchboard interlocked bus--section section

switches should be provided switches should be provided

(65)

(66)

Radial distribution diagram for typical small commercial building – meters on

(67)

3.2 Internal Power Distribution

System

C) Rising Mains C) Rising Mains--11

1) Cable, including prefabricated tee

1) Cable, including prefabricated tee--off cable.off cable.



 The selection of cable as rising mains is usually limited by its The selection of cable as rising mains is usually limited by its gg yy yy

current carrying capacity (CCC) current carrying capacity (CCC)



 The cable may be singleThe cable may be single--core insulted cable, or multicore insulted cable, or multi--core core

dd blbl armoured

armoured cable.cable.



 For singleFor single--core, core, p.v.c.p.v.c.--insulated. Noninsulated. Non--armouredarmoured cable, the largest cable, the largest

cross sectional area is 1000mm2 giving a CCC of 1200A cross sectional area is 1000mm2 giving a CCC of 1200A cross sectional area is 1000mm2 giving a CCC of 1200A. cross sectional area is 1000mm2 giving a CCC of 1200A.



 As a rule of thumb, when the demand exceeds 800A, As a rule of thumb, when the demand exceeds 800A, busductbusduct is is

preferred. preferred. pp

(68)

3.2 Internal Power Distribution

System

c) Rising Mains c) Rising Mains--22 2) Insulated

2) Insulated busductbusduct (or (or busbarbusbar) system, including feeder type ) system, including feeder type and plug

and plug--in type in type busductbusduct..



 The rating of The rating of busductbusduct could be up to 5000A or even higher. The could be up to 5000A or even higher. The

provision of plug

provision of plug--in unit provide flexibility for teein unit provide flexibility for tee--off at any location/ off at any location/ floor at anytime when demand required

floor at anytime when demand required floor at anytime when demand required. floor at anytime when demand required.



 The bus may be insulated conductor or bare conductors totally The bus may be insulated conductor or bare conductors totally

enclosed in continuous steel

enclosed in continuous steel trunkingtrunking.. enclosed in continuous steel

(69)

3.2 Internal Power Distribution

System

c) Rising Mains c) Rising Mains--33

The following factors affect the selection of the type of rising main: The following factors affect the selection of the type of rising main:

L d L d



 Load assessmentLoad assessment 

 Load distributionLoad distribution 

 Environmental conditions such as ambient temperature and humidityEnvironmental conditions such as ambient temperature and humidityEnvironmental conditions such as ambient temperature and humidityEnvironmental conditions such as ambient temperature and humidity 

 Heights of riserHeights of riser 

 Maximum allowable voltage dropMaximum allowable voltage drop

F lt l l F lt l l



 Fault levelFault level 

 Likelihood of alternation and future extension/ expansion being frequently Likelihood of alternation and future extension/ expansion being frequently

required required



 form, types and usage of the buildingform, types and usage of the building 

 whether the wiring is to be installed during the construction of a building, in whether the wiring is to be installed during the construction of a building, in

a completed building, or as and extension system. a completed building, or as and extension system. a completed building, or as and extension system. a completed building, or as and extension system.



 Capital outlay requiredCapital outlay required 

(70)

3.2 Internal Power Distribution

System



d) Sub

d) Sub--main

main -- 11

Any building of more than four floors including the Any building of more than four floors including the



 Any building of more than four floors including the Any building of more than four floors including the

ground floor and designed for occupation of more ground floor and designed for occupation of more than one consumer shall be provided with 3 phase than one consumer shall be provided with 3 phase than one consumer shall be provided with 3 phase than one consumer shall be provided with 3 phase electrical rising mains with 3 phase and neutral tee electrical rising mains with 3 phase and neutral tee--off at each floor

off at each floor off at each floor off at each floor



 Type of rising mains could be one of the followings:Type of rising mains could be one of the followings:

I l t d d t i

I l t d d t i tt kiki // d itd it



 Insulated conductors in Insulated conductors in trunkingtrunking/ conduit;/ conduit; 

 ArmouredArmoured cables suitably supported;cables suitably supported;

Bare conductors in

Bare conductors in trunkingtrunking



(71)

3.2 Internal Power Distribution

System



d) Sub

d) Sub--main

main -- 22

Each riding mains installation shall be protected Each riding mains installation shall be protected



 Each riding mains installation shall be protected Each riding mains installation shall be protected

against

against overcurrentovercurrent and earth leakage and shall be and earth leakage and shall be equipped with suitable means of isolation

equipped with suitable means of isolation equipped with suitable means of isolation. equipped with suitable means of isolation.



 For For busbarbusbar installation having a rated capacity not installation having a rated capacity not

di 400A i h h f 3 h 4 i

exceeding 400A in each phase of a 3 phase 4 wire exceeding 400A in each phase of a 3 phase 4 wire system, the associated neutral

system, the associated neutral busbarbusbar should have a should have a cross

cross sectional area not less than the crosssectional area not less than the cross sectionalsectional cross

cross--sectional area not less than the crosssectional area not less than the cross--sectional sectional area of the phase

(72)

3.2 Internal Power Distribution

System



d) Sub

d) Sub--main

main -- 33

Rise

Rise ea thing

ea thing cond cto fo m lti

cond cto fo m lti tenant

tenant



Riser

Riser earthing

earthing conductor for multi

conductor for multi--tenant

tenant

installations shall be installed and the

i i

i

f i

i i

i

f i

thi

d t

i

minimum size of riser

minimum size of riser earthing

earthing conductor is

conductor is

70mm

22

_copper.



The loadings on 3 phase rising mains should

be properly balanced. The neutral conductor

should have a suitable current carrying

capacity to cater for any imbalance or

harmonic current.

(73)

3.2 Internal Power Distribution

System



d) Sub

d) Sub--main

main -- 44



The design of rising mains installation should

be agreed by the electricity supplier.

g

y

pp



No part of the communal installation should

pass through any individual consumers unit

within the multi

within the multi--consumer building.

consumer building.



No cable, other than that for lift installation

governed by BS5655, shall be run in lift shaft.

g

y

,

(74)

3 3..2

2 Internal Power Distribution

Internal Power Distribution

System



e) Lateral Mains

e) Lateral Mains -- 11

Adequate space for lateral mains and meter board Adequate space for lateral mains and meter board



 Adequate space for lateral mains and meter board Adequate space for lateral mains and meter board

wiring shall be provided in meter room. wiring shall be provided in meter room.

Th l di 3 h l t l i h ld b



 The loading on 3 phase lateral mains should be The loading on 3 phase lateral mains should be

balanced as far as practicable. balanced as far as practicable.



 An installation requiring more than 60A is required to An installation requiring more than 60A is required to

be arranged to service a 3

be arranged to service a 3--phase supply.phase supply.



 Appropriate correction factors shall be applied for Appropriate correction factors shall be applied for

determining the current carrying capacity of cables. determining the current carrying capacity of cables.

(75)

3.2 Internal Power Distribution

System



e) Lateral Mains

e) Lateral Mains -- 22

Distribution board switchgear and

Distribution board switchgear and busbarbusbar chamberchamber



 Distribution board, switchgear and Distribution board, switchgear and busbarbusbar chamber chamber

should have phase identification. should have phase identification.

Wh bl d t d t th h



 Where cables, conducts, ducts pass through Where cables, conducts, ducts pass through

structural element such as floors and walls, the structural element such as floors and walls, the

i h ll b l d b i t fi i t t

openings shall be sealed by appropriate fire resistant openings shall be sealed by appropriate fire resistant materials. In addition, internal fire

materials. In addition, internal fire--resistant barriers resistant barriers shall be provided to prevent the spread of fire

shall be provided to prevent the spread of fire shall be provided to prevent the spread of fire. shall be provided to prevent the spread of fire.



 Segregation of lowSegregation of low--voltage circuits, fire alarm circuits voltage circuits, fire alarm circuits

d t l h / t l i ti i it h ll b

and telephone/ telecommunication circuits shall be and telephone/ telecommunication circuits shall be made when they run together.

(76)

3.2 Internal Power Distribution

System



e) Lateral Mains

e) Lateral Mains -- 33

Connection between the electricity supplier

Connection between the electricity supplier’’s meters meter



 Connection between the electricity supplierConnection between the electricity supplier’’s meter s meter

and the consumer

and the consumer’’s main switch should be not less s main switch should be not less

than 4mm

than 4mm22 _{stranded copper conductor}_{stranded copper conductor}

than 4mm

than 4mm2 2 _{stranded copper conductor.}_{stranded copper conductor.}



 The insulation and/ or sheath of the cables shall be The insulation and/ or sheath of the cables shall be

d f di t f 150 f th

removed for a distance of 150mm from the removed for a distance of 150mm from the

connection, and replaced if necessary by suitable connection, and replaced if necessary by suitable heat

heat resisting insulation when connecting the cable toresisting insulation when connecting the cable to heat

heat--resisting insulation when connecting the cable to resisting insulation when connecting the cable to bare conductors/

(77)

3.2 Internal Power Distribution

System



e) Lateral Mains

e) Lateral Mains -- 44

Warning notice

Warning notice ““DANGERDANGER”” in red legible letter within red legible letter with



 Warning notice Warning notice –– ““DANGERDANGER”” in red legible letter with in red legible letter with

Chinese translation shall be displayed near each Chinese translation shall be displayed near each

distribution board Each character shall not less than distribution board Each character shall not less than distribution board, Each character shall not less than distribution board, Each character shall not less than 10mm high.

10mm high.

Wh i t ll ti i t d t i i i



 Where an installation is connected to rising mains, Where an installation is connected to rising mains,

agreement should be obtained from the owner of agreement should be obtained from the owner of rising mains if new current demand exceed that rising mains if new current demand exceed that rising mains if new current demand exceed that rising mains if new current demand exceed that before. Moreover, prior approval from the power before. Moreover, prior approval from the power company should be obtained before any alteration company should be obtained before any alteration company should be obtained before any alteration company should be obtained before any alteration work is carried out.

(78)

3.2 Internal Power Distribution

System

f) Installation methods of cables

According to he CP for WP or IEE Wiring Regulations According to he CP for WP or IEE Wiring Regulations



 According to he CP for WP or IEE Wiring Regulations, According to he CP for WP or IEE Wiring Regulations,

cables can be in the following ways: cables can be in the following ways:

O li d di t



 Open or clipped directOpen or clipped direct 

 Embedded direct in building ,materialsEmbedded direct in building ,materials 

 In conduit In conduit 

 In truckingIn truckingIn truckingIn trucking 

 In free air, on cleats, brackets or ladderIn free air, on cleats, brackets or ladder 