electricity
DESCRIPTION
electricTRANSCRIPT
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.