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1.1 Introduction to Power System
Power System is a network of high tension wires/cables by which the
generated Electrical power is transmitted and distributed throughout a
region.
Power System consists of the following main components:
Generation System- Energy Conversion Methods
Transmission System- Ultra-high, Extra-high, High and Medium
Voltage levels
Distribution System- Low voltage levels
The Load or Energy sink- Residential, Commercial and Industrial
loads
1. Fundamentals
3. 3
Types of Energy Conversion Methods/Generation Systems:
1. non- conventional (renewable energy sources )
are sources that are continuously replenished by natural
processes.
PV System, Solar Thermal, Hydropower, Wind Power, Geothermal,
Biomass (Renewable conversion systems)
2. Conventional (non-renewable energy sources )
Are sources that are not continuously refilled by natural
processes
•Diesel Generator, Gas Turbine, Steam Turbine, Coal power
plant, Nuclear power (Conventional systems)
1.Generation System
Power System main components
4. 4
2. Transmission Systems:
This component of the power system transmits the bulk electrical energy
from generation stations where it is produced to the main load centres.
The transmission system is composed of:
• Step-up and Step-down substations
• Transmission lines
3.Distribution Systems
The distribution system gives out the energy from the medium voltage
substations to customers’ location. It is composed of:
• Medium Voltage (MV) lines (33kV, 15 kV)
• MV/LV transformer substations (33/15/ kV to 400/380/220 V)
• Distribution lines (33/15 kV, 380 V 3-phase and 220 v single phase)
4. Load or Energy Sink:
Load is the end equipment of the power system where the transmitted
electrical energy is converted to other forms of useful energy.
Cont’d
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• In early days, there was a little demand for electrical energy so that
small power stations were built to supply lighting and heating loads.
• However, the widespread use of electrical energy by modern
civilization has necessitated producing bulk electrical energy
economically and efficiently.
• The increased demand of electrical energy can be met by building big
power stations at favorable places where fuel (coal or gas) or water
energy is available in abundance. This has shifted the site of power
stations to places quite away from the consumers centers.
• The electrical energy produced at the power stations has to be
supplied to the consumers. There is a large network of conductors
between the power station and the consumers. This network can be
broadly divided into two parts viz., transmission and distribution.
8. Non-Conventional Energy Sources
Renewable energy sources also called non-conventional
energy, are sources that are continuously refilled by natural
processes.
A renewable energy system converts the energy found in
- sunlight
- wind
- falling-water
- sea-waves
- geothermal heat or
- biomass
9. Solar Energy
Solar energy can be utilized trough two different routs
Solar thermal rout.
Solar thermal route uses the sun's heat to produce hot water
or air, cook food, drying materials etc.
Solar electric rout(Photovoltaic) rout.
Solar photovoltaic uses sun’s heat to produce directly
electricity for the applications such as; lighting home and
building, running motors, pumps, electric appliances, and
lighting.
10. Solar Electricity Generation
Solar Photovoltaic (PV): Photovoltaic is the technical
term for solar electric. Photo means "light" and voltaic
means "electric".
PV cells are usually made of silicon, an element that
naturally releases electrons when exposed to light.
Amount of electrons released from silicon cells
depend upon intensity of light incident on it.
The silicon cell is covered with a grid of metal that
directs the electrons to flow in a path to create an
electric current.
This current is guided into a wire that is connected to
a battery or DC appliance.
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Wind Power
The wind is a free, clean, and inexhaustible energy source.
It has served humankind well for many centuries by propelling
ships and driving wind turbines to grind grain and pump water.
Denmark was the first country to use wind for generation of
electricity.
One of the most critical features of wind generation is the
variability of wind. Wind speeds vary with time of day, time of
year, height above ground, and location on the earth’s surface.
Wind energy is basically harnessing of wind power to
produce electricity. The kinetic energy of the wind is
converted to electrical energy.
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Wind Energy Technology
1. Horizontal-axis turbines, in
which the axis of rotation is
horizontal with respect to the
ground (and roughly parallel to
the wind stream.)
2. Vertical-axis wind turbines, in
which the axis of rotation is
vertical with respect to the
ground (and roughly
perpendicular to the wind
stream),
16. Bio Energy/Biomass Energy
Biomass is a renewable energy resource derived from the
carbonaceous waste of various human and natural
activities. It is derived from numerous sources, including
the by-products from the wood industry, agricultural
crops, raw material from the forest, household wastes etc.
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Hydro-power
Hydroelectric power generation involves the storage of a
hydraulic fluid, water, conversion of the hydraulic (potential)
energy of the fluid into mechanical (kinetic) energy in a
hydraulic turbine, and conversion of the mechanical energy
to electrical energy in an electric generator.
The early generation of electricity from about 1880 often
derived from hydro-turbines, and the capacity of total
worldwide installations has grown at about 5% per year
since.
Hydro-power now accounts for about 20% of world’s electric
generation. Output depends on rainfall and the landscape.
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Hydropower Generation
The term hydro-power is usually restricted to the generation of shaft
power from falling water. The power is then used for direct mechanical
purposes or, more frequently, for generating electricity.
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Tidal Energy
• Tidal electricity generation
involves the construction of a
bombardment across an
estuary to block the incoming
and outgoing tide. The head
of water is then used to drive
turbines to generate
electricity from the elevated
water in the basin as in
hydroelectric dams.
22. Geothermal Energy
The temperature of the ground or groundwater a few feet beneath the Earth’s surface remains relatively
constant throughout the year, even though the outdoor air temperature may fluctuate greatly with the
change of seasons. At a depth of approximately six feet, for example, the temperature of soil in most of
the world’s regions remains stable between 45º and 70°. This is why well water drawn from below
ground tastes so cool even on the hottest summer days.
Utilizes the Earth’s inner heated rocks to heat water that reaches these areas through seismic faults.
This water is turned to steam then captured to operate steam-powered generators.
24. Conventional Energy sources
Is a stocks of energy Not continuously refilled using
natural process.
They are:
Fossil fuels - Coal, Oil, & Natural Gas
Nuclear fuel –
25. Natural gas
A natural gas is a mixture of different gases the main ingredient is
Methane, a natural compound that is made from the decay of plant
and animal remains.
Nuclear Fission
Splitting uranium atoms produces a great deal of heat energy that is
processed into electrical energy in nuclear plants.
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• The conveyance of electric power from a power station to
consumers’ premises is known as an electric supply system.
• It consists of three principal components viz., the power station,
the transmission lines and the distribution system.
• Electric power is produced at the power stations which are
located at favorable places, generally quite away from the
consumers. It is then transmitted over large distances to load
centers with the help of conductors known as transmission lines.
• Finally, it is distributed to a large number of small and big
consumers through a distribution network.
• The electric supply system can be broadly classified into (i)
DC. or AC. system (ii) overhead or underground system.
Electric Supply System
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Comparison of AC and DC transmission
• The electric power can be transmitted either by means of DC. or AC.
Each system has its own merits and demerits. It is, therefore, desirable
to discuss the technical advantages and disadvantages of the two
systems for transmission of electric power.
DC transmission.
• For some years past, the transmission of electric power by DC. has
been receiving the active consideration of engineers due to its
numerous advantages.
Advantages.
• (i) It requires only two conductors as compared to three for AC.
transmission.
• (ii) There is no inductance, capacitance, phase displacement and surge
problems in DC. transmission.
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42. 42
• (iii) Due to the absence of inductance, the voltage drop in a DC.
transmission line is less than the AC. line for the same load and
same sending end voltage. For this reason, a DC. transmission line
has better voltage regulation.
• (iv) There is no skin effect in a DC. system. Therefore, entire cross-
section of the line conductor is utilized.
• (v) For the same working voltage, the potential stress on the
insulation is less .Therefore, a DC. line requires less insulation.
• (vi) A DC. line has less corona loss and reduced interference with
communication circuits.
• (vii) The high voltage DC. transmission is free from the dielectric
losses, particularly in the case of cables.
• (viii) In DC. transmission, there are no stability problems and
synchronizing difficulties.
Cont’d Advantages
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(i) Electric power cannot be generated at high DC. voltage due
to commutation problems.
• (ii) The DC. voltage cannot be stepped up for transmission of power
at high voltages.
• (iii) The DC. switches and circuit breakers have their own
limitations.
A.C. transmission.
• Now-a-days, electrical energy is almost exclusively generated,
transmitted and distributed in the form of a.c.
Advantages
• (i) The power can be generated at high voltages.
• (ii) The maintenance of AC. sub-stations is easy and cheaper.
• (iii) The AC. voltage can be stepped up or stepped down by
transformers with ease and efficiency.
Disadvantages
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• This permits to transmit power at high voltages and
distribute it at safe potentials.
Disadvantages
• (i) An AC. line requires more copper than a DC. line.
• (ii) The construction of AC. transmission line is more
complicated than a DC. transmission line.
• (iii) Due to skin effect in the AC. system, the effective
resistance of the line is increased.
• (iv) An AC. line has capacitance. Therefore, there is a
continuous loss of power due to charging current even
when the line is open.
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Comparison of Sources Power based on
Merits and Demerits
Merits of Coal Thermal Plant
Coal is cheap and available in abundance at present.
It is a time tested process, so no experimentation is
required.
Less space required as compared to Hydro based
station and less hazardous than Nuclear power plant.
Less initial cost as compared to other conventional
process of power generation.
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Cont’d…
Demerits of Coal Thermal plant
Calorific value (Kcal/Kg) of Indian coal is very low and
large ash content.
Huge volume of ash is produced daily and it’s disposal is
burning issue today.
Atmospheric pollution is very high.
Transportation of coal to plant and transmission of
generated power to load centre involves large expenses.
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Cont’d…
Advantages of Nuclear Power Generation
Less quantity of fuel for generation of given amount of energy
compared to other sources.
High reliability, Efficient and less running cost.
Disadvantages of Nuclear Power Generation
Fuel is expensive and not available in abundance
everywhere.
High capital cost.
Maintenance cost is very high.
Nuclear waste disposal is a great problem.
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Cont’d…
Advantages of Hydro Power Generation
Once a dam is constructed, electricity can be produced at a
constant rate
If electricity is not needed, the sluice gates can be shut,
stopping electricity generation
The build up of water in the lake means that energy can be
stored until needed, when the water is released to produce
electricity.
The lake's water can be used for irrigation purposes.
Hydropower is fueled by water, so it's a clean fuel source.
Hydropower doesn't pollute the air like power plants that burn
fossil fuels, such as coal, oil or natural gas.
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Cont’d…
Disadvantages of Hydro Power Plant
Dams are extremely expensive to build and
must be built to a very high standard.
People living in villages and towns that are
in the valley to be flooded, must move out.
Hydro power plants can be impacted by
drought. When water is not available, the
hydro power plants can't produce electricity.
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Cont’d…
Advantages of Wind Energy System
The wind is free and with modern technology it can be
captured efficiently.
Once the wind turbine is built the energy it produces, does
not cause green house gases or other pollutants.
Remote areas that are not connected to the electricity
power grid can use wind turbines to produce their own
supply.
Wind turbines are available in a range of sizes which
means a vast range of people and businesses can use
them.
Single households to small towns and villages can make
good use of range of wind turbines available today.
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Cont’d…
Disadvantages of Wind Power
The strength of the wind is not constant and it
varies from zero to storm force.
This means that wind turbines do not produce the
same amount of electricity all the time.
There will be times when they produce no
electricity at all.
Wind turbines are noisy.
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Cont’d…
Advantages of Solar Energy Systems
After initial investment, all the electricity produced is
free.
Incentives and rebates from government and utility
companies offset the initial investment.
Clean, renewable energy source.
No transmission costs for stand alone systems.
Virtually no maintenance and no recurring costs
Ideal for remote locations that cannot be tied to the grid
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Cont’d…
Disadvantages of Solar Energy
High initial cost to purchase solar panel system
A relatively large area is required to install a solar
system
The highest efficiency is dependent on full sun
exposure
No electricity can be produced at night, and reduced
production on cloudy/rainy days
