Hydro Electric power plant
Hydroelectric power is the power obtained by converting potential energy in a height of water which is
converted to kinetic energy of turbine then alternator used to convert this energy into electrical energy.
Schematic Arrangement of hydro power plant
Elements of Hydro Electric power plant
1. Storage Reservoir :
• Store the water during the rainy season and supply
same during the lean flow period.
2. Dam :
• Store the water during the rainy season and supply
same during the lean flow period.
• Function of dam is to create Artificial head
• Storage of water for irrigation
• Water for drinking purpose
3. Spillway :
• It act as a safety valve.
• it discharge the overflow water for flood control.
4. Tail Race :
• The water after doing useful work in a turbine is
discharge through the tail race.
5. Surge tank :
• Reduction in a load on a generator cause close turbine
gate thus, the pressure created in Penstock.
• This can be avoid by providing a small Storage or tank for
receiving and relieving the flow of water
6. Penstock :
• it is the path by which water flow.
7.Power house :
• The powerhouse is a building in which the turbine alternator and other axillaries are housed.
8. Switch yard for transmission of power :
• the electrical equipment of a hydroelectric power station included Transformer circuit breaker and other
switching and protective devices
Nuclear power plant
• Energy is converted into electrical energy is known as a nuclear power station.
• The main sources of nuclear energy are uranium 𝑈 235 and Thorium 𝑇ℎ232 .
Schematic diagram of nuclear power station
Load curve
• The curve showing the variation of load on power
Station w.r.t time is know as load curve.
• Connected load
• Maximum demand
• Demand factor
• Average Load
• Load factor
• Diversity factor
• Plant capacity factor
• Plant use factor
Base load and peak load on power station
• Base load :
• The unvarying load which occurs almost the whole day
on the station Is know as base load.
• Peak load :
• The various peak demand of load over and above the
load of the station is know as peak load.
Cost of electrical energy
1. Fixed Cost : it is the cost which is independent of maximum demand and unit generated.
2. Semi-Fixed Cost : cost depend upon maximum demand but it is independent of unit generated.
3. Running Cost : it is the cost which depends only upon number of unit generated.
Tariff
The rate at which electrical energy is supplied to a consumer is known as tariff.
• Cost of Producing Electrical energy
• Cost of capital investment in transmission and distribution system
• Cost of operation and maintenance of supply electrical energy : Metering equipment,
billing etc.
• Types of Tariff :
• Simple Tariff
• Flat rate tariff
• Block rate tariff
• Two part tariff
• Maximum demand tariff
• Power Factor tariff
• Three part tariff
Wind power generation
Wind turbine convert kinetic energy of the wind into mechanical energy and generator
which is couple with the Wind Turbine convert mechanical energy into electrical energy.
Schematic diagram of Wind power plant
Parts of the wind turbine
1. Rotor : The Blade of the router are connected to the main shaft. The rotor will run and passed a wind energy
to the main shaft.
2. main shaft : Turns the gearbox.
3.Generator : which generate the electricity
4. Anemometer : it is the wind instrument which measure the speed of wind and send is information to
the controller.
5. The wind Vane : tells the controller the direction of the wind.
6. Controller : it is the brain of a wind turbine. The controller turn off determine at a higher wind speed to avoid
damaged to the different parts.
7. Tower : It is made from a steel or a steel lattice.
Terminology used in a wind power generation
• Efficiency of windmill = Power developed by wind mill
Wind energy available on rotor of wind mill
• Swept area : projected area of the Wind mill.
• Cut in speed : it is the speed of the wind at which generator start developing power.
• Cut out speed : when speed of wind is very high and dangerous for a
wind turbine generator must be isolated from its operation.
• Rated wind speed : the speed of a wind when a generator is producing a rated a power.
• Wind velocity : The measurement of the speed at which wind is moving at a specific direction.
• Wind Farm : A project where number of windmills collecting installed at place and generate electricity is
called wind farm.
Wind energy conversion
• Power in wind
• Windmill works on the principle of converting kinetic energy of wind to
mechanical energy.
• The energy available is the kinetic energy of the wind.
• Let,
Wind velocity or speed = V m/sec
Density of air = 𝜌 𝑘𝑔/𝑚3
Area through which air pass = A sq. m
m = mass of air traversing through area a swept by the rotor blade .
m= 𝜌 A V
1
• K. E. Kinetic energy of moving Air = 𝑚𝑣 2
2
Substituting the value of mass m in the expression for kinetic energy.
1
Κ.Ε. = (𝜌 A V) 𝑣 2
2
1
= (𝜌 A 𝑣 3 ) (Available Kinetic energy )
2
• Where,
A = area of horizontal axis aero – turbine
𝜋𝐷2
A=
4
1 𝜋𝐷2
• Available wind power = 𝜌 ( ) 𝑣3
2 4
1
= 𝜌𝜋𝐷2 𝑣 3
8
• Power obtain from the above equation in watt,
• wind power 𝛼 𝐷2
• wind power 𝛼 𝑣 3
P 𝛼 𝑣3
Power curve of wind turbine
Types of wind turbine
• Squirrel-Cage rotor Induction Generator (SCIG)
• Wound-Rotor Induction Generator (WRIG)
• Doubly-Fed Induction Generator (DFIG)
• Synchronous Generator
• Permanent Magnet Synchronous Generator (PMSF)
Solar power generation
Introduction to solar energy
• The energy from the sun comes as a result as fusion of hydrogen into helium
under high temperature and pressure.
• This process release huge amount of electromagnetic radiation energy.
Solar radiation Spectrum
• The electromagnetic wave emitted from the sun are known as solar
radiation.
• The solar radiation are actually carries of solar energy.
Types of solar radiation
1. Beam or direct radiation
• The solar radiation which are received on the earth surface directly without having change
its direction are called beam radiation or the direct radiation.
2. Diffused radiation
• When solar rays pass through clouds, they get diffused because the cloud contain
suspended particles, water vapor and gases. The radiation are scattered reflected and
reflected due to which its energy is very much reduced.
3. Total radiation
• They are also called as Global radiation. Total solar energy falling on a unit area on any part
of the earth is called total radiation.
Solar Photovoltaic cell
Solar Cell definition
• A solar cell is an electrical device that transforms light energy directly into electrical energy using the
photovoltaic effect.
Construction of solar cell
• It consists of a p-n junction. The n-side of the junction faces the solar radiation. The p-side is
relatively thick and is at the back of the solar cell.
• Both the p-side and the n-side are coated with a conducting material. The n-side is coated with
an anti-reflection coating which allows visible light to pass through it. The main function of this
coating is to reflect the IR (heat) radiations and protect the solar cell from heat.
• This coating works as the electrical contact of the solar cell. The contact on the n-side is called
the front contact and that at the p-side is called the p-side is called the back contact or the rear
contact.
• The n-side of a solar cell is thin so that the light incident on it reaches the depletion region
where the electron-hole pairs are generated.
Working of solar cell
• It generates emf when radiations fall on the p-n junction. A solar cell is of two types p-
type and n-type.
• Both types use a combination of p-type and n-type silicon which together forms the p-n
junction.
• In solar cells, electron-hole pairs are generated due to the absorption of light near the
junction.
• Electrons move towards n-type silicon, holes move towards the p-type silicon layer.
• Electrons reaching the n-side are collected by front contact and holes reaching p-side are
collected by back electrical contact.
• Thus potential difference is developed across solar cells. When an external load is
connected, photocurrent flows through it.
• Many solar cells are connected in series or parallel to form solar panels or modules.
Solar Photovoltaic (SPV) system
• A typical cell develop voltage in the range of 0.5 to 1.0 V and current density of 20-30
mA/cm². To obtain higher voltage and current the cell are mounted on a suitable backup
board and connected in series and parallel to form a module.
• The behavior of the solar cell can be represented by its current voltage characteristics.
• The intercept on x-axis is called short circuit assent Isc and y-axis is called open circuit voltage
Voc. The maximum useful power is equal to the area of the largest rectangle formed under
the curve.
Im. 𝑉𝑚
• The ratio of is called the fill factor (F.F.) of the cell.
𝐼𝑆𝐶 . 𝑉0𝐶
• Its value varies between 0 and 1.
• It can be expressed by the equation,
𝑃
Conversion efficiency =
𝐸 𝑥 𝐴𝐶
• Where, 𝑃 = Maximum power
𝐸 = solar constant
A = Area
Electrical supply system
Generating station - G.S represents the generating station of electric Power is produced by 3
phase alternators operating in parallel. The usual generation voltage is 11 KV . for economy In the
transmission of electric Power, the voltage is stepped up to 132 KV at the generating station with
the help of 3 phase transformer.
Primary transmission - the electric power at 132 KV is transmitted by 3 phase 3 wire, overhead
system to the outskirts of the city. This forms the primary transmission.
Secondary transmission - At the receiving station, the voltage is reduced to 33 KV by step down
transformer. from this station, electric Power is transmitted at 33 KV by 3 phase 3 wire overhead
system to various sub-station located at the strategic points in the city. This forms the secondary
transmission.
Primary distribution - The secondary transmission line terminated the substation where voltage is
reduce from 33 KV to 11 KV, 3 phase 3 wire. The 11 KV line run along the important road side of
the city. This forms the primary distribution.
Secondary distribution - The electric power from primary distribution line 11KV is delivered to
distribution substation. This sub-station are located near the Consumers localities and step down
the voltage to 400 V, 3- phase , 4-wire for secondary distribution. The voltage between any to
phase is 400V and between any phase and neutral is 230 V.
CLASSIFICATION OF TRANSMISSION SYSTEM
1. On the basis of type of voltage :
• D.C. system
• A.C. system
2. On the basis of physical arrangement:
• Overhead system
• Under ground system
3. Scheme of connection
• Radial system
• Ring main system
• Inter-connected system
4. On the basis of level of system voltage:
• Medium voltage system (66 kV)
• High voltage system (132 kV, 220 kV or more which include HVAC and HADC
Advantages of high voltage for transmission
• Transmission of electric power is carry out at a high voltage due to following reasons:
1. for the given power, cost of conductor material required is less. i.e. it reduce the cost of
conductor material.
2. Efficiency of Transmission increase .
3. Percentage line voltage drop is reduced.
(1) Reduced the cost of conductor material
• Let 'P' be the power in kW, transmitted by a three phase transmission line at a line voltage
of V volts and cos is the power factor of the load.
• The power transmitted in a 3-phase system is given by the relation ;
P = 3 𝑣 ⋅ 𝐼 cos 𝜙
𝑝
• 𝐼=
3 .𝑣 . cos 𝜙
• Resistance 'R' of each conductor is given as ;
𝑙
𝑅= 𝜌
𝑎
• Total line losses, w = 3. 𝐼 2 . 𝑅
2
𝑃 𝑙
w = 3. 2
.𝜌
3𝑣 cos ∅ 𝑎
𝑝2 𝜌 𝑙
w=
𝑣2 . cos2 ∅. 𝑎
• Area of cross-section of each conductor,
𝑝2 𝜌 𝑙
𝑎=
𝑣2 . cos2 ∅. 𝑤
• It is clear from above equation that larger the transmission voltage, lesser is the area of cross
section of the conductor.
Comparison of D.C. and A.C. Transmission
D.C. transmission Advantages :
• The high voltage dc. transmission has the following advantages over high a.c transmission :
• It requires only two conductors as compared to three for ac. transmission.
• There is no inductance, capacitance, phase displacement and surge problems in dc. transmission.
• 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 sending end voltage. For this reason, a d.c. transmission line has better
voltage regulation.
• There is no skin effect in a de. system. Therefore, entire cross-section of the line conductor is
utilized.
• For the same working voltage, the potential stress on the insulation is less in case of d.c. system
than that in ac. system. Therefore, a de. line requires less insulation.
• A d.c. line has less corona loss and reduced interference with communication circuits.
• The high voltage de. transmission is free from the dielectric losses, particularly in the case of cables
• In d.c. transmission, there are no stability problems and synchronizing difficulties.
• Disadvantages :
• Electric power cannot be generated at high de voltage due to commutation problems.
• The d.c. voltage cannot be stepped up for transmission of power at high voltages
• The d.c. 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
(1) The power can be generated at high voltages.
(2) The maintenance of ac. sub-stations is easy and cheaper.
(3) The ac. voltage can be stepped up or stepped down by transformers with ease and efficiency.
This permits to transmit power at high voltages and distribute it at safe potentials.
Disadvantages
• An ac. line requires more copper than a d.c. line.
• The construction of a.c. transmission line is more complicated than a d.c. transmission
line.
• Due to skin effect in the ac. system, the effective resistance of the line is increased.
• An ac. line has capacitance. Therefore, there is a continuous loss of power due to charging
current even when the line is open.
Comparison between the over head system and under ground system
Base Over head system Under ground system
Appearance Appearance is not good due to over head Wires etc. are not seen so the appearance is
wires, insulators, jumpers, cross arms etc. good
Maintenance Maintenance is more as the wires, Maintenance is less as the cable is under the
insulators etc. are in open ground.
Possibility of fault Pos the conductors are in open, possibility Possibility of occurring fault is comparatively
of occurring fault is less as the cable is under the ground.
Safety Safety is less as the wire may break and There is more safety
cause harm to the living beings
Possibility of More Less
lightening stroke
Voltage drop As the spacing of the wires is more, the Inductance is less due to the closed
inductance is more so voltage drop is more conductors, so the voltage drop is less due to
due to the inductive reactance the inductive reactance
Fault location and Fault location is easy and repairing is also Fault location is not easy and repairing is
repairing easy difficult
ELEMENTS OF TRANSMISSION LINE
The following are the elements of the over head a. c. transmission line.
1. Step up transformer: This transformer is kept in the switch yard of the generating station. This
transformer steps up the generated voltage to the voltage of transmission.
2. Line supports: Steel towers are used to support the conductors of the transmission line.
3. Line insulators: Suspension and strain type porcelain insulators are used to insulate the conductors
from the ground.
4. Conductors: Copper conductors were used for the transmission line but ACSR conductors are now
widely used in place of copper conductors due to the increased price of copper.
5. Step down transformer: Step down transformer is provided at the end of the transmission line
which steps down the primary transmission voltage to the secondary transmission voltage.
6. Protective devices: For the protection of the equipment of the transmission circuit breakers, earth
switch, lightening arresters, ground wires, arcing horns etc. are used.
7. Regulators: Voltage regulators are provided for the voltage regulation of line and for the
improvement of the power factor of the line, the synchronous condensers are provided at the end of
the transmission line.
Connection schemes of distribution system
Radial system
Ring main system Inter-connected system
Types of D.C distributors
Distributor fed at one end Distributor fed at both end
Distributor fed at center
Ring main
