Transcript Power System

EE 207: Fundamentals of
Electrical Power Systems
Chapter 2
Power Systems: An
Overview
Introduction
Power System
Support Components
Measurement &
Monitoring System
Generation
Transmission
Protection System
Distribution
Main Components
Load
Supply of Electricity
Electrical Systems
Demand
• Electricity energy cannot be stored.
• Generate electricity based on demand.
• Total power drawn by consumer fluctuates
depends on the time of day and seasons.
• Demand Curve
– Plot each demand of electricity by consumer
daily/annually
Demand Curve
Load Duration Curve
• 3 types of load
– Base load
• Has to be fed 100% of the time.
– Intermediate loads
• Have to be fed <100% of the time.
– Peak load
• May occur 0.1% of the time.
Load Duration Curve
Plot the duration of each demand on annual based.
Peak Load
(2MW)
Demand (GW)
•
Intermediate Load
(4MW)
Base Load
(6MW)
Time in %
100% : 8760hrs
Load Duration Curve
• Base-power stations
– Deliver full power at all times
– Nuclear, coal-fired, hydro stations,…
• Intermediate-power stations
– Respond relatively quickly to changes in demand
– Usually by adding/removing generating unit
– Hydropower stations
• Peak-power stations
– Deliver power for brief intervals during the day
– Put into service very quickly
– Equipped with prime movers that can be started up in
a few minutes
– Diesel, pumped-storage turbines, gas turbines etc.
Power System Diagram
Generation
Power Station
Step-up transformer (↑ voltage,↓current)
Main Intake/Large
Sub-Station
Grid System (500kV, 275kV, 132kV, 66kV)
Reduce the voltage
Sub-Station 33kV,11kV
Sub-Station
Transmission
Sub-station
Sub-station
Rural Transformer
Industrial:
Factory, Industries
Commercial:
Towns, Offices
Residential
3 phase - 415 V, single phase - 240 V
Distribution
Loads
Power System
AROUND TOWN &
RESIDENTIAL AREA Underground distribution to
individual premises is at
415 volts and 240 volts.
HOUSE - Overhead distribution
to individual houses is at 240
volts.
LIGHT INDUSTRY Most small factories
receive their electricity at
11,000 volts
HEAVY INDUSTRY - Some have
direct connections to the
transmission at 132,000 volts.
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
High voltages of 500kV, 275kV, 132kV are
used for transmitting electricity over the grid
system
A transformer in a large sub-station
reduces the voltage to 33kV, 22kV,11kV
Supplies to rural
communities are
often reduced from
11kV to domestic
voltages (415/240V)
by pole mounted
transformers.
Generation
• At power generating station (generating
voltage)  11 – 20kV and frequency of 50
Hz
• Transform to higher voltage (transmission
voltage)  132kV, 275kV and 500kV
• Transform to lower voltage (distribution
voltage)  33kV or 11kV
Worldwide Commercial Energy Production
Coal
Oil
Natural Gas
Hydro-electricity
Percent of total electricity generation as hydro-electricity
Norway
Brazil
Iceland
Columbia
Venezuela
Canada
Switzerland
New Zealand
Chile
Sweden
0
20
40
60
Percent Hydro Power in 2005
80
100
Electricity generation capacity
(Ontario, Canada)
•
•
•
•
•
Hydro-Québec sources of energy supply (2013)
Hydro (96.8%)
Other Renewables (2.9%)
Nuclear (0.2%)
Thermal (0.1%)
Generation Capacity
in Malaysia
• Generation capacity of major power producer
Generation Capacity
• Generation Plant Mix
TNB Power Stations
Hydroelectric
Power Plant
Under construction
Coal-fired Power Plant
Combustion Turbine
Power Plant
Transmission
• To ensure the adequacy and reliability of supply
that are fundamental needs of modern society.
• Provides the link between electricity suppliers
and electricity consumers.
• Helps reduce energy prices since generation in
other regions which are cheaper can be
channeled to customers.
• Transmission connects regional systems via
inter-connectors to encourage cooperation for
mutual benefits.
Transmission System
• Lines/transformers operating at voltages
above 100 kV are usually called the
transmission system.
• Consists of Transmission Line and Substations
• Transmission network of 500kV, 275kV
and 132kV known as National Grid.
Transmission Line
Components
• Transmission Line
– Overhead Lines
– Cable
• Underground Cables
• Submarine Cables
• Sub-stations
Transmission Line
• Components
– Tower support structure
– Cross-arms
– Conductors
– Insulators
– Earth-wires
Transmission tower
Waist-Type
Tower
Double Circuit
Tower
Guyed-V-Tower
Transmission Tower
Overhead Line
Conductors
Insulators
Sub-station
• Size of substation
– Depends on transformer size
• Types of Sub-station
– Conventional outdoor
• Require bigger space
– GIS (gas insulated switchgear)
• Less space
• Outdoor or indoor
Outdoor Sub-station
GIS
Sub-station
Components
•
•
•
•
•
Transformer
Circuit Breaker / Switch Gear
Isolator Switches
Busbar
Protection Relay & Control Equipment
Power Transformer
Circuit Breaker
Spark gap. In event
of a lightning strike
on the line, the
current can jump the
gap between that ball
and the protrusion on
the tank, and make a
path to earth. This
prevents overloading
the breaker.
Circuit Breaker
Distribution
• Lines/transformers operating at voltages
below 100 kV are usually called the
distribution system.
• Part of the electric utility system between
the bulk power source and the customer
service entrances (loads).
• 33kV, 22kV, 11kV, 6.6kV, 415V and 240V
Distribution Sub-station
• Distribution Intakes (33kV, 22kV)
• Distribution Substations (22kV, 11kV, 6.6kV)
–
–
–
–
–
Indoor substation
Outdoor substation
Pole mounted substation
Compact substation
Underground substation
• Transformer capacity
– 100kVA, 300kVA, 500kVA, 750kVA and 1000kVA
Distribution Intake
Indoor Sub-station
Underground
Sub-station
Compact Sub-station
Outdoor Sub-station
Pole-Mounted
Sub-station
Distribution
Transformer
Distribution
Circuit Breaker
Load
• Types of Load:
– Residential
– Commercial
– Industrial
– Public Transportation
– Public Lighting
– etc.
Residential Load
• Consist of lighting, radio, TV, refrigerator,
kitchen appliances, washing machine and
etc.
• Usually, increases in the evening around 6
p.m. and return to a nominal value around
12 p.m.
Commercial Load
• Consists of lighting, air-condition and
small appliances.
• Shops, business premises, schools,
universities etc.
• The load is fairly constant from 9am
until 9pm with the exception of any
mid-day break.
Industrial Load
• Mainly consists of motor load, air
conditioner, lighting, welding and
furnaces etc. It can be divided into
small, medium and large category.
The nature of industrial load curve will
depend on the number of shifts
worked in the industry.
Electricity Consumers
National Grid System
Advantages
• Provide multiple paths between various
generation sources and loads
• Provide for power transfers from one
geographic area to another to achieve
overall system operating economics
• Interconnect the bulk power facilities of
individual power station/utilities so that
they can better withstand major
disturbances
Advantages
• Other advantages:
– Stability
• Load sharing
– Continuity of service
• Maintenance, breakdown
– Economy
• Cheap & efficient
Interconnection
• Peak lopping; imports during peak load
(morning) and export during lower demand
(evening)
• Economic power exchange; export if its price is
lower than other and vice versa
• Help each other during system
emergencies/crisis
Load Dispatch Centre
(LDC)
• Objectives:
– Grid system requires a grid controller/operator
system.
– In order to ensure the supply of energy is safe
and reliable.
LDC Function
• Maintains system stability
– Frequency control
– Voltage within limits
• Achieve minimum operating cost
– Optimize transmission losses
– Merit order generation
• maintain spinning reserve requirements
• co-ordinate generation and transmission
maintenance outages
• Restoration of supply after system fault
Future ASEAN Power
Supply Interconnection