electricity

NOOR AISYAH ASYIKIN

D416

QSM 554

ELECTRICITY

Electricity is a flow of electric charge along

a wire. The more charge that are

passing along the wire the larger the

current

Two types : Positive and

negative

Magnitude of force :

Coulomb’s law

SI unit of electricity = coulomb

= quantity of electricity

Electric Current = flow of electron along a conductor that forced by generator/ battery, to a consuming device then back to the source

BASIC OF ELECTRICITY

Figure 1: Current flow in an electric circuit

2 Types of electric current = AC and DC

Alternating Current (AC) = varies periodically in value and directions

more economical - ability to change the voltage levels by using transformers

Direct Current (DC) = has a constant flow in one direction

low-voltage applications, eg: batteries which can only produced DC.

BASIC OF ELECTRICITY

Ampere (A) - a unit of the rate of flow of electric current,

eg := 1 ampere represents a current flow of one coulomb of charge per second

Volt (V) - electrical force that causes free electrons to flow along a conductor

Ohm (Ω) - the unit of electric resistance of a conductor

TERMINOLOGY OF ELECTRICITY

TERMINOLOGY OF ELECTRICITY

Ohm’s Law V = I x Rwhere

V is the applied voltage, measured in volts

I is the current, measured in amperes

R is the resistance, measured in ohms

Figure 2: Relationship between V, I and R in Ohm’s Law

CONDUCTOR vs. INSULATOR

CONDUCTOR = A material where electric current flows

Copper and aluminium are commonly used

Good conductors have a low resistance to the flow of electricity

INSULATOR = a materials that do not conduct electricity

E.g. glass, ceramic and plastics

They are used on electrical devices to provide protection from the electricity

POWER AND ENERGY

ENERGY- term used to express work = kilowatt-hours (unit)

POWER = rate at which energy is used = watts (unit)

i.e. a WATT is one ampere flowing under an electromotive force of one volt

Relationship : W = I2 R (watts – ampere2 x ohms)

TRANSFORMER

Distribution need for long distance transmission efficiency, and yet customer safety, reconciled by use of transformer

Transformer comprises primary input and secondary input windings around a common metal loop, and the respective number of windings determines whether the voltage is stepped up or down.

Figure 4: ‘Step-up’ and ‘step-down’ transformer

THE ELECTRICAL SUPPLY SYSTEM

INVOLVES 4 MAIN PROCESSES

1. Generation

4. Supply

Figure 5: Transmission, distribution and supply system

GENERATION, TRANSMISSION, DISTRIBUTION & SUPPLY

Transmission, distribution and supply system

Turbine

substation

Step-uptransformer

Step-downtransformer

Generation station

Step-downtransformer

Lines : Overhead/underground

Lines : Overhead/underground

Lines : Overhead/underground

Transmission

Distributors

Supplier

Consumer

Consumer

Service cable

Water, steam etcPylons

ELECTRICITY GENERATION

Electricity generation is the first process in the delivery of electricity to consumers

The process which involves the generation of electricity

Electricity is generated in power stations by using a form of energy sources such as; water (hydroelectric), steam, gas, solar, nuclear and battery.

At power station, electric power is produced at 11-20 kV and frequency 50 Hz.

SOURCE AND GRID

Most power-station alternators are driven by steam, generated by heat of fossil-fuel combustion, nuclear reaction, solar geothermal or hydroelectric

Figure 3 : Hydroelectric schemes

RESERVOIR

river, sea, waterfalls

TURBINE

mechanical energy

Electricity produced

GENERATORAC/DC

types of SOURCES Sources can be divided into 2 groups:

Renewable – replace in a reasonable period of time by natural process that we can use over and over again

e.g hydro, wind, solar, wave, tidal, biomass, geothermal

Non-Renewable - an energy source that we are using up and cannot recreate in a short period of time

e.g coal, natural gas, oil, uranium

TYPES OF SOURCES

reservoir transformer

water

valve

Water passage

Switch room

turbine

Figure : Hydroelectric power plant

HYDROELECTRIC power plant

Hydroelectric power plant

Turbine room

HYDRAULIC TURBINE &

ELECTRICAL GENERATOR

ADVANTAGES

Economics

some plants now in service having been built 50 to 100 years ago

Operating labor cost is usually low since plants are automated

sale of electricity from the dam will cover the construction costs after 5 to 7 years of full generation

Related activities

provide facilities for water sports, and become tourist attractions

fish farm with relatively constant water supply

boats may be used to improve transportation.

No pollution.

generates no nuclear waste nor nuclear leaks

ADVANTAGES

Environmental damage

can be disruptive to surrounding aquatic ecosystems

changes the downstream river environment

many native and migratory birds have become increasingly endangered

DISADVANTAGES

Sediment build up and dam failure.

enemy bombardment during wartime, sabotage and terrorism

the Banqiao Dam failure in China resulted in the deaths of 171,000 people and millions homeless

Population relocation

relocate the people living where the reservoirs are planned

historically and culturally important sites can be flooded and lost

DISADVANTAGES

Process in the generation of electricity in a hydroelectric power plant

In hydroelectric schemes, they are turned by water pressure from the reservoir.

The power station is constructed at the bottom of the reservoir.

A water passage will connect the reservoir with the turbine room. This is where the water will run down.

The flowing (or falling) water from the reservoir will push against the turbine blades, causing the rotor to spin. (cont’d)

Process in the generation of electricity in a hydroelectric power plant

Then, the turbine will turning the copper inside the generator and generating an electric current

Next, the electric current will be transferred to the transformer at the switch room.

The power then is pooled into the National Grid, a countrywide network cables.

ELECTRICITY TRANSMISSION & DISTRIBUTION

The transmission system consist of :

High voltage cables (transmission lines)

Transformers Substations

Pylons (transmission towers)

ELECTRICITY TRANSMISSION

ELECTRICITY TRANSMISSION

Electricity is transmitted via high voltage cables using 3 phase supply

The voltage is stepped up or down by using transformers

The use of high voltage enables a large amount of energy to be transmitted through smaller diameter cables.

The supply of electricity is transmitted in the form of alternating current (AC).

At Power Station, electric power is produced at 11-20kV.

The power is then transformed to higher voltages (132kV ,200kV or 275kV) using power transformer AND

ELECTRICITY TRANSMISSION

transferred through the Transmission System to substations where voltage is lowered to 33kV or 11kV.

The Distribution System begins after this point.

ELECTRICITY TRANSMISSION

Generation, Transmission & Distributions

Transmission system is a system of high voltage network which interconnects main generating stations with major load substation

The system enables bulk transfer of power between these transmission points.

In Peninsular Malaysia it is known as National Grid.

The voltages at which bulk power transfer takes place in the National Grid are:

i) 132kV

ii) 275kV

iii) 400kV

ELECTRICITY TRANSMISSION

Transmission system is a system of high voltage network which interconnects main generating stations with major load substation

The system enables bulk transfer of power between these transmission points

In Peninsular Malaysia it is know as National Grid

The voltages at which bulk power transfer takes place in the National Grid are:

1. 132kV

2. 275kV

3. 400kV

ELECTRICITY TRANSMISSION

National Grid System

Power generated by large power stations are transmitted a transmission system called ‘grid’

In Malaysia, the whole power transmission is through the National Grid System (refer related figure)

Benefits:

i. Enable bulk transfer over long distances

ii. Standardize electrical frequency and voltage to customers

iii. Permitted transfer of electricity throughout the country

iv. Infrastructure spin off

Disadvantages

Requires high capital cost for infrastructure, generating stations, substations, equipment, etc.

Requires high degree of management & maintenance

Requires a long time to complete the whole grid (& connection to other countries)

National Grid System

National Grid, Malaysia is the primary electricity transmission network linking the electricity generation, transmission, distribution and consumption in Malaysia

Operated and owned by TNB. More than 420 substations in Peninsular Malaysia are linked together by the extensive network of transmission lines operating at 132, 275 and 500 kilovolts (kV).

Power generated by Tenaga Nasional and independent power producers is carried by the National Grid towards customers connected to the various distribution networks.

National Grid System

A steel mills take power directly from the transmission grid.

It was founded on 1959. The first line on the national grid was the transmission line from Tanjung Kling in Melaka to the city of Melaka.

Tenaga Nasional - with 11,296 MW installed capacity.

Malakoff - with 4,393 MW installed capacity.

Powertek - with 1,490 MW installed capacity.

YTL Power - with 1,212 MW installed capacity

National Grid System

IPP LOCATIONCAPACITY

(MW)DATE OF ISSUE OF

LICENSE

YTL Power Generation

Paka, Terengganu Pasir Gudang, Johor

808 404 7 April 1993

Segari Energy Ventures Sdn. Bhd. Lumut, Perak 1,303 15 July 1993

Powertek Sdn Bhd. Alor Gajah, Melaka

440 1 Disember 1993

Port Dickson Sdn. Bhd. Tanjung Gemuk, Port Dickson

440 1 Disember 1993

Pahlawan Power Sdn. Bhd Tanjung Keling, Melaka

334 26 May 1999

Genting Sanyen Power Sdn Bhd Kuala Langat, Selangor

720 1 July 1993

IPPs in Malaysia generate and sell electricity in bulk to the 3 dominant utilities.The IPPs, which are in operation, are as follows:

Peninsular Malaysia

National Grid System

National Grid System

Alor Setar

Butterworth

Ipoh

Kuala Lumpur

SerembanMelaka

Kluang

Johor Baru

Kota Bharu

Transmission Maintenance Offices

OVERHEAD LINE

275kV132kV66kV

500kV6,1999,998

171

890Length

(circuit-km)

CABLE

275kV132kV66kV

49674

-

Length

(circuit-km)

TRANSFORMERS

275kV132kV66kV

500kV26,21338,258

410

4,500Transformation

Capacity

(MVA)

(17,258)

(723)

(69,381)

SUBSTATIONS

275kV132kV66kV

500kV67

2995

4Number of

Substations

(TNB)

(375)

OVERHEAD LINE

275kV132kV66kV

500kV6,1999,998

171

890Length

(circuit-km)

CABLE

275kV132kV66kV

49674

-

Length

(circuit-km)

TRANSFORMERS

275kV132kV66kV

500kV26,21338,258

410

4,500Transformation

Capacity

(MVA)

(17,258)

(723)

(69,381)

SUBSTATIONS

275kV132kV66kV

500kV67

2995

4Number of

Substations

(TNB)

(375)

Kuantan

Transmission System

TURBINE GENERATING STATIONS

STEP – UP TRANSFORMERS

Pylon/tower

Lines: Overhead/underground

Water, steam etc

11 kV22 kV33 kV

132 kV275 kV400 kV

TRANSMISSION

THE TRANSMISSION AND DISTRIBUTION SYSTEM

POWER STATION- Generator

output at 11,000/20,000 volts is

stepped up by transformer to

132,000 275,000 and 500,000 volts

for transmission.

TRANSMISSION - Transmission is mainly at 132,000 275,000 and 500,000 volts

HEAVY INDUSTRY - Some have

direct connections to the

transmission at 132,000 volts.

LIGHT INDUSTRY -Most small factories

receive their electricity at

11,000 volts

HOUSE - Overhead

distribution

to individual houses is at 240

volts.

AROUND TOWN &

RESIDENTIAL AREA -Underground distribution to

individual premises is at

415 volts and 240 volts.

TRANSMISSION COMPONENTS

1. PYLON

2. TRANSFORMER

3. TRANSMISSION LINES

4. SUBSTATIONS

PYLON / TOWER LINE

A pylon is a lattice steel structure used to support overhead electricity conductors for power lines.

Pylons at which sections of conductor start, finish or change direction are called strainer pylons.

They may need anchor wires to counterbalance the weight of the conductors on the opposite side or be designed to deal with the forces imposed on them.

The conductors are supported by horizontal strings of conductors.

TOWER LINE / PYLON

TOWER LINE / PYLONcrossarm Horizontal element that protrudes on each side of the pylon; it supports the bundles by means of suspension insulator strings.

suspension insulator string Insulators that are assembled in a vertical or oblique chain; the overhead line conductors hang from it.

bundle Conductor cables that are kept a constant distance apart by spacers; they are used to transport current.

K-frame Part of the pylon that rests on the waist; it has two branches that end at the beam gantry.

node Point at which several legs and bars come together.

panel Part of the pylon between two horizontal members.

horizontal member Horizontal bar that connects the main legs to strengthen them.

main leg The main tower legs of the pylon body; they support mainly vertical weights.

base width Space between the foundation axes of the main legs.

pylon foot Lower part of the pylon that is usually underground; the legs are anchored to it.

pylon body Part of the pylon support between the top and the foot.

diagonal Diagonal bar that connects two main legs or a horizontal member and a main leg.

waist Demarcation bar between the pylon top and body that is held tightly between them.

pylon window Space bounded by the inner side of the arms of the K-frame and the beam gantry.

pylon top Upper portion of the pylon where the insulator strings and bundles are attached.

TRANSFORMER

A transformer is an electrical device that transfers energy from one circuit to another purely by magnetic coupling.

Relative motion of the parts of the transformer is not required for transfer of energy.

Transformers are often used to convert between high and low voltages, to change impedance, and to provide electrical isolation between circuits.

TRANSFORMER

132kV/33kV

TRANSFORMER 33kV/11kV

Electrical transformers are used to "transform" voltage from one level to another, usually from a higher voltage to a lower voltage. They do this by applying the principle of magnetic induction between coils to convert voltage and/or current levels

In this way, electrical transformers are a passive device which transforms alternating current (otherwise known as "AC") electric energy from one circuit into another through electromagnetic induction.

TRANSMISSION LINES

A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electric currents, magnetic fields, acoustic waves, or electromagnetic waves.

Examples of transmission

lines include wires, optical

fibers and coaxial cables.

coaxial cables.

SUBSTATION

A substation is the part of an electricity transmission and distribution system where voltage is transformed from low to high and vice versa using transformers.

A substation that has a step-up transformer increases the voltage whilst decreasing the current, while a step-down transformer will decrease the voltage while increasing the current for domestic and commercial distribution.

TRANSMISSION OPERATION

TNB remains a major player in electricity generation and distribute the electric to premises and range of business activities

The electricity is supplied from generator station or power station.

The current of electricity from the power station will transmits to PMU through Tower Line which carried up the voltage of 132kv .

PENCAWANG MASUK UTAMA (PMU)

From the substation, electricity will be reduced to 33kV in the transformer.

Electricity will then be supplied to consumers (Factories, Businesses, Houses, etc) by Distribution through overhead lines and underground cables

Trunking

Then, from the Transformer the flow of the electricity entered into PMU through ‘Trunking’ or underground cables.

CONTROL PANEL TRANSFORMER 33kV & 11kV

The current from Transformer which through the Trunking will be control by Control Panel in PMU.

Control Panel in PMU

VACUUM CIRCUIT BREAKER 11kV

VACUUM CIRCUIT BREAKER 33kV

CONTROL

PANEL

33kV

CONTROL PANEL 11kV

OVER HEAD - 33kV

From the Vacuum Circuit Breaker 33kv, the current will go out to electric pole (over head) 33kV, then send to PPU near the PMU.

Pencawang Pembahagi Utama

PENCAWANG PEMBAHAGIAN UTAMA (PPU)

In PMU, a room to place a battery needed for safety and security which the battery used to make sure the flow of the electricity in a good condition if any emergency case happen. The battery will be switch on in 24 hours non stop

OPERATION

The electricity will be transmitted directly to PPU after the electricity is distributed at PMU.

The purpose: to reduce the voltage and for the next distribution processes.

Reduce from 33kV to 11kV.

The 33kV currents will go thought and transformed by the transformer.

Controlled by Transformer Control Panel 33kV / 11kV.

Transformer will reduce the 33kV current to 11kV current.

The current will be transferred to VCB for distributed to the substation.

The components at PPU :

Transformer

Control Panel 33 kV & 11 kV

Vacuum Circuit Breaker (VCB)

Battery

Charger Box

TRANSFORMER 33 kV

CONTROL PANEL

CONTROL PANEL 33kV

CONTROL PANEL 11kV

VACUUM CIRCUIT BREAKER 33 kV

VACUUM CIRCUIT BREAKER 11 kV

CHARGER BOX

BATTERIES

TNB SUB-STATION

After the distribution process in PPU

completed, the current will be delivered to nearest sub- station.

The total current from PPU is 11KV

The transformer will be reduce current again from 11KV to 415V in the sub-station.

OPERATION

Components are used in the sub-station as following : Transformer

Switch Gear

High Voltage Fuse Unit (HFU)

Out Going Unit

Feeder Pillar

SWITCH GEAR & CONTROL HFU

TRANSFORMER

Then, the total current 415V transferred through by Out Going Unit to FeederPillar.

This current will be distributed for customers.

OUT GOING UNIT

FEEDER PILLAR

When the current have in Feeder Pillar. Amount of current will be reduce again to distributed for the costumer.

415V = 240V

The method using to transfer the total current 240V for single phase system by over head.

For three phase system, the current electric will be sent to the buildings from the Feeder Pillar.

Normally three phase system have the big current. it is about 415V.

It is always use for the building which it need more current electric.

The current 415V also can sent by over head.

ELECTRIC POLE (OVER HEAD)

DISTRIBUTION SYSTEM

Distribution System is the process of transmission of electricity from major load centers to consumers

Power is further distributed to load centers/substations where voltages are further reduced (by using transformers) before reaching factories, homes etc.

Generally, the distribution voltages in Malaysia are 33kV, 11kV and 415/240 Volts.

DISTRIBUTION SYSTEM The electricity distributed to varies power plant from the main power

plant with the ‘step-down’ volts before it will be supplied

System commonly used are grid system.

Figure 7: Distribution system

Lines : Overhead/underground

Step-downtransformers

Step-downtransformers

substation

Distributor

Supplier

SUPPLY SYSTEM

SUPPLY SYSTEM

TNB Supply System

Power Plant

‘Step-up’ Transformers

‘Step-down’ Transformers

Sub-station

‘Step-down’ Transformers

Overhead/Underground)

Transmission

Distribution

Supply

Consumer

Overhead Pole

• Voltage 3 phase (50Hz)•Main transmission network: 275kV, 132kV, 66kV

•Distribution network: 33kV, 22kV (for limited area), 11kV, 6.6kV(limited area), 415V, 240V(single phase)

•Low voltage system (415/240V): 3 phase 4 lines (415V) / single phase 2 lines (240V)

•This system is a combination of overhead lines and underground cables

SUPPLY SYSTEM

Power stations generate electricity at 25kV alternating current (AC), 50 Hertz

The high current produced enables the voltage to be transformed up to 132, 240, 400 and 500kV.

SUPPLY SYSTEMDiagrammatic Installation of Single Phase For Single Unit Dwelling

Substation

Cut out board/sealing

chamber

Meter

Distribution Board (DB)

Power circuit

External

Internal

- Consumer control board- Consumer control unit

Supply to domestic buildings can be of 2 form:-Overhead cables-Underground (about 0.5m below ground)

Domestic buildings are supplied with the single phase supply - contains a live phase and a neutral in one cable and terminating at the meter board

SUPPLY SYSTEM Distributor will ‘step-down’ the voltage of the power to be supplied to the

consumer, and it is transmitted with overhead and underground lines

Figure 8: Supply system

Step-downtransformers

Lines : Overhead/underground

Service cable

Supplier

consumer

consumer

SUPPLY TO A BUILDING

CONSUMER SUPPLY SYSTEM

Standard reduced voltage

400 kV

240 kV Generation and distribution

132 kV

33 kV Large / heavy industries, cities, towns and railways

11 kV Light industries, hospitals, towns and villages

400 V Small industries, offices, farms

240V Housing, schools, small commercial premises

AC, 3-phase supply with 4-wire cable

AC, 3-phase supply with 3-wire cable

DC or AC, single-phase supply with 2-wire cable

Types of electricity supply

a) normal supply from the supply authority such as TNB

- May be taken at high voltage (11kV) or low voltage(415v)

- Depending on the maximum demand of the installation and/or technical requirement

b) standby supply provided by diesel generator set

- required by Jabatan Bomba to provide the necessary power to certain equipment in the building i.e lifts, fire fighting system, emergency lighting etc. in the event of normal supply failure

SUPPLY TO A BUILDING

CONSUMER SUPPLY SYSTEM

3-phase supply system provides 73% more power than single-phase, for additional of wire

Figure 9 : 3-phase and single-phase supply system

3 phase wiring. Note the 3 wires (red, yellow and blue) and the 3 fuses.

Some newer housing come 3 phase wiring ready. Note the same 3 phase wiring (red, blue and yellow) but only 1 fuse is installed.

3 PHASE WIRING SYSTEM

METERING

Watt-hour meter – a meter for measuring recording the quantity of electrical power consumed with respect to time

Meter circuit consists of 2 coils:a) The current coil connected across the phase

b) The voltage coil across the phase and neutral

METERING

SUPPLY TO A BUILDING

3 types of distribution for large & high-rise buildings

i) Radial distribution

ii) Ring-main distribution

iii) Rising main distribution

SUPPLY TO A BUILDINGRADIAL system

The electrical supply radiates from the main intake panel.

The main panel consists of a main switch connected to fused switches through a bus-bar chamber

Several separate cables are run from the main intake panel to sub-subsidiary distribution panels which may be situated in separate buildings or strategic points in one building.

Example of radial distribution are factories and resort complexes.

SUPPLY TO A BUILDINGRADIAL system

SUPPLY TO A BUILDING

RING Main system

In the case of a large development scheme having several

buildings around the perimeter of site , a ring main circuit is provided.

The ring main circuit would be taken around the site into each

building

The ring main distribution system has the following advantages :

i) Each building and individual sections may be isolated

without switching off the entire installation

ii) The current flow in either direction can reduce voltage

drop

Example : holiday resorts, small factory complexes and residential complexes

SUPPLY TO A BUILDING

RING Main System

SUPPLY TO A BUILDING

Rising main distribution

For buildings five storey and above, it is normally

preferable to pass conductors vertically through the

building

The supply to each floor is connected to the rising

mains by means of tap-off subsidiary units

Rising

main distribution

SUPPLY TO A BUILDING

DOMESTIC BUILDINGS

Domestic supply is AC, single-phase, 240 volts, i.e.

each house tapped-off the 3-phase street supply in

rotation

Consumer board serve individual circuits for e.g.

cooker, ring circuits for general power, and lighting

Fuse inserted to protect each stage in distribution

hierarchy, deliberate weak link. Always on live side

of circuit, sometimes on neutral also.’

Earth ensures circuit fuses e.g. if appliance casing

becomes live.

Switches at least on live side, or on neutral also, i.e.

‘double-pole’.

SUPPLY TO A BUILDING

DOMESTIC BUILDINGS

Figure 10: Typical domestic electrical distribution system

a) 3-phase supply along street from

neighbourhood transformer, with

single-phase tap-off to houses

b) Consumer unit

Consumer unit(intake point for domestic building)

The consumer's power supply control unit, conveniently summarised as a consumer unit, is a rationalisation of several circuit boxes containing a switch and fuse for isolation of individual circuits.

The unit is located as close as possible to the meter, but on the inside of the building for convenient access.

A two-pole main switch usually rated at 100 A controls the supply to several outgoing circuits or 'ways'.

Each way is rated in amperes, the value depending on the circuit purpose.

Consumer unit(intake point for domestic building)

Circuit protection is by semi-enclosed rewirablefuse, cartridge fuse or miniature circuit breaker (MCB).

Up to 16 ways are available for domestic use and a typical example is shown in the following figure.

Within the unit are a phase or live bar between fuses and isolator and an unfused neutral bar connected to the isolator.

An unswitched earthing terminal is also provided.

Consumer unit

Consumer unit/Distribution Board/Distribution Panel

A panel for distributing power to other panels or to motors and other heavy power consuming loads

Intake - domestic

Most domestic supplies are buried underground and contain a phase and neutral in one cable, terminating at the meter cupboard.

In more remote areas the supply may be overhead.

The termination and metering services cables to buildings is determined by the electricity authority’s supply arrangements.

Figure : service cable supply to external supply cupboard

SUPPLY TO A BUILDING

DOMESTIC BUILDINGS

Figure 10: Typical domestic electrical distribution system

C - Power ring

circuit

D - Remote switching loops off lighting circuit

SUPPLY TO A BUILDING

LARGER BUILDINGS

11kV possibly maintained to large building’s own

transformer; thence, 415/240 volts to meters and main

distribution board

3-phase busbars in distribution board; 3-phase

individual supplies tapped-off to plant; 3-phase rising

busbars to local distribution boards for power and

lighting

Single-phase power and light circuit tapped-off boards;

typically conduited under floors or over ceilings, with

tap-offs to sockets and lights respectively

Fluorescent light circuits sometimes continued at 3-

phase, in which case cables well separated to avoid

415-volt shock danger

SUPPLY TO A BUILDINGLARGER BUILDINGS

Figure 11: Electrical distribution sequence in multi-storey office building

1

4

32

5

Served by underground 11kV ring main

direct from the substation

SUPPLY TO A BUILDING

LARGER BUILDINGS - BUSBARS

Figure 12: 3-phase busbars

• Busbar in electrical power distribution refers to thick strips of copper or aluminium that conduct electricity within a switchboard, distribution board, substation, or other electrical apparatus.

•The size of the busbar is important in determining the maximum amount of current that can be safely carried.

•Busbars can have a cross-sectional area of as little as 10 mm² but electrical substations may use metal tubes of 50 mm in diameter (1,000 mm²) or more as busbars.

SUPPLY TO A BUILDING

LARGER BUILDINGS - BUSBARS

Figure 12: 3-phase busbars

• Bus conductors of

rectangular cross section

• Assembled in a sheet-

metal trough

• Consists 4 metal strips,

live240V (R, W and B) and

neutral line

• Used for separating the 3-

phase supply into single-

line / lower current

• Found in main switchboard

to connect the main switch

to fused switches

SUPPLY TO A BUILDING

LARGER BUILDINGS – RISING BUSBARS

Figure 12: 3-phase busbars riser

• Used in high-rise building

• Used to distribute 415V 3-phase electricity from main distribution

board to all floors

• Copper vertical busbars which run

up in electricity cable riser

• Vertical duct / trunking to the

height of the building

• To prevent the spread of fire and smoke, fire barriers are

incorporated with the busbar chamber at each compartment

floor level.