Textbook of Basics of Electrical Engineering 4th Module "Generating stations,Transmission and distribution of electric power"

1. Module 4
Generating stations, transmission
and distribution of electric power

2. Generating stations
• Electric energy is considered superior to all other forms of
energy
• Cheaper, economical for all purpose of uses
• Very convenient form of energy- can be converted into
other forms
• A generating station generates electricity
• A generating station essentialy employs a prime mover
coupled to an alternator.
• Prime mover converts some form of energy into
mechanical energy.
• Alernator converts mechanical energy to electrical energy

3. • Generating stations are classified as mainly,
 Hydro-electric power stations
 Thermal stations
 Nuclear power stations
 Diesel power stations

4. Hydro-electric power stations
• Is a power plant utilizing the potential energy
of water at a high level for the electricity
generation.
• The main requirement is a dam with a high
head water content.
Schematic arrangement of a hydro –electric
plant

8. Advantage of Hydro-electric power
stations
• No fuel is required by such plants as water is the source of
energy. Hence operating costs are low.
• The plant is highly reliable and it is cheapest in operations
and maintenance.
• It is very neat and clean plant because no smoke or ash is
produced
• Such plant are robust and have got longer life.
• Highly skilled engineers are required only at the time of
construction but later on only a few experienced person
will be required.
• Such plants in addition to generation of electric power also
serve other purpose such as irrigation and flood control.

9. Disadvantages
• It requires large area
• Its construction cost is very high and takes
long time for erection.
• Long transmission lines are required as the
plants are located in hilly areas which are
quite away from the load centre.
• There is uncertainty about the availability of
huge amount of water due to dependence of
weather conditions.

10. Thermal stations( steam power plants)
• The heat of combustion of fuels (coal, oil, or gas ) is
utilized by the boilers to raise steam at high pressure
and temperature.
• Steam produced used in driving the steam turbines
coupled to generators.
Schematic arrangement
the plant can be divided into four main circuits.
1. Fuel and ash circuits
2. Air and fuel gas circuits
3. Feed water and steam circuit
4. Cooling water circuit

13. • Fuel and ash circuit
o Fuel from the storage fed to boiler through fuel
feeding device
o Ash produced by combustion collects and
removed to ash storage through ash handling
equipment.
• Air and fuel gas circuit
o Forced draught fan draws atmospheric air
through air- pre heater
o It heated by flue gsses passing to chimney. Then
pass to furnaces.
o Flue gases after passing boiler and super heater
drawn by induced draught fan through
economizer and air pre heater finally to chimney.

14. • feed water and steam circuit
o Condensed water is extracted from the condenser by
condensate pump then forced to HP feed water heater
where its temperature raised by bled steam.
o It is then pumped to boiler through economizer in
which it is further heated by flue gasses.
o In boiler water is converted into high pressure steam,
which is wet
o Wet steam is passed through super heater, where it
dried then supplied to steam turbine
o In condensor heat extracted from steam and converted
to feed water
• Cooling water circuit
o circulate through the condensor to condense the steam
and discharges at the source it self.

15. Advantages of steam power plant
• Fuel used is cheaper
• Less space is required in comparison with that of
hydroelectric plants
• Cheaper in initial cost in comparison with other
types of power plants of same capacity
• Cheaper in production cost in comparison with that
of diesel power plant
• Such plants can be installed at any place irrespective
of the existence of fuels, while hydro-electric plants
can be developed only at the source of water power

16. disadvantages
• High maintenance and operating costs
• Pollution of atmosphere due to fumes and residues
from pulverized fuels
• Requirement of water in large quantity
• Handling of coal and disposal of ash is quite difficult
• Requires long time for erection and put into action

17. Nuclear power plants
• Nuclear energy is converted to electrical
energy.
• Main fuels are uranium and thorium.
• Fuel subjected to nuclear fission releases large
amount of energy.

21. Advantages of nuclear power plants
• The amount of fuel required is very small, therefore ,
there is no problem of transportation, storage etc.
• These plants require less area as compared to any
other type
• These can be located near the load centers, therefore
primary distribution cost is reduced
• These plants are most economical in large capacity
• There are large deposits of nuclear fuels available all
over the world. Therefore such plants can ensure
continued supply of electrical energy for thousands of
years

22. disadvantages
• The initial capital cost is very high as compared to
other types of power plants
• The erection and commissioning of the plant requires
greater technical knowledge
• The fission by products are generally radio-active and
may cause a dangerous amount of radio active
pollution
• Fuel is expensive
• The disposal of products, which are radio-active, is a
big problem. They have either to be disposed off in a
deep trench or in a sea away from sea-shore

23. Non conventional energy sources
• The non conventional energy sources are
Sun
Wind
Tidal
geothermal

24. Solar power generation
• Sun is the prime source of energy
• The solar electrical energy is of special
importance in India that
I. There is a need for conservation of fossil fuel
resources, such as gas, oil, coal etc
II. There is a need for reducing atmospheric and
thermal pollution which are having serious
detrimental effects on our environment.
III. There is a need for supply of electrical
energy in remote areas.

25. Solar thermal system

27. • Advantages
1. Renewable source: no fuel required
2. There is no pollution
• Disadvantage
1. Main disadvantage is sun energy available for
only part of the day, and cloudy and hazy
atmospheric conditions effects most
2. Cost is large
3. Solar tracking system required for sun angle
tracking

28. Solar photo voltaic systems (SPV)

29. • Advantage
1. renewable source
2. No pollution
3. No moving parts, so maintenance cost low
4. Long life
• Disadvantages
1. High cost
2. Generation possible for 6 hours during day time
only
3. Output is in DC. So DC-AC converter is requires

30. Tidal energy
• Tides will rise and fall due to change in
gravitational force.
• The rised tide stored in some area, it may
increase upto meters
• And this head used to rotate a turbine.

31. Wave energy

32. Wind energy

33. • Advantages
1. Renewable energy source
2. No pollution
3. Installation can made fast
4. Round the clock availability
• Disadvantages
1. Weather dependent
2. Most of the time plant may operate at a lower
output compared to capacity
3. May create noise pollution
4. May damage in extreme wind speed conditions
5. Large area required

34. Geothermal energy
• Using heat from interior of the earth energy is
converted to electrical energy.
• Two main techniques
o To use hydrothermal sources
o To extract heat from hot dry rocks.

35. Transmission & distribution
of electric power

36. Various systems of power transmission
• DC systems
i. DC two wire
ii. DC two wire with mid point earthed
iii. DC three wire system
• Single phase AC systems
i. Single phase two wire
ii. Single phase two wire with mid point earthed
iii. Single phase three wire
• Two phase AC systems
I. Two phase four wire
II. Two phase three wire
• Three phase AC systems
i. Three phase three wire
ii. Three phase four wire

37. Comparison of dc and ac transmission
• DC
• Advantages of dc transmission
i. Requires two conductor
ii. no inductance, capacitance and phase
difference
iii. No skin effect
iv. Free from most of the losses
• Disadvantages of dc transmission
i. Cannot step up or step down
ii. Generation is difficult

38. • AC
• Advantages of AC transmission
i. Possible to generate high voltage
ii. Can step up or step down
iii. Maintenance of ac substation is easy and cheap
• Dis advantages of AC transmission
i. Require more conductor than dc
ii. L, C affects regulation
iii. Due to skin effect effective resistance increases
iv. Construction of ac transmission line is more
complex

39. Advantage of high transmission voltage
• Volume of conductor is reduced and hence
the cost is less
• Voltage drop in the lines is reduced
• Efficiency of transmission line is increased

40. Power transmission scheme

41. • Primary transmission
Transmission line network connects generating
stations with main substations. Main voltage
levels are 66, 110, 132, 220, 400kV.
• Secondary transmission
link between main receiving end substation to
secondary substations. voltage levels 66, 33kV
• Primary distribution
Line supply power from substation to distribution
transformer. mainly 11kV. Consumers with load
more than 50kW supplies 11 kV
• Secondary distribution
Three phase 4 wire n/w. low tension low power
consumers. Normalyv415/240 V

42. Primary distribution

43. Secondary distribution

44. • Feeders
• Distributors
• Service mains

45. substation
• Classification of substations
1. According to service requirement
a) Transformer substations
b) Switching sub stations
c) Frequency changer sub stations
d) Converting substations
2. According to constructional features
a) Indoor substations
b) Outdoor substations
c) Underground substations

46. Pole mounted substation

47. Substation equipments
1. Bus bars
2. Insulators
3. Isolators
4. Circuit breaker
5. Power transformer
6. Current transformer
7. Potential transformer
8. Protective relays
9. Lightning arresters
10.Carrier current equipment

48. Advantage of underground system
over overhead system of power
distribution
1. More safe
2. Low maintenance cost
3. Very few chances of fault
4. Few chances of accident
5. Good appearance
6. Free from lightning effects
7. No interference with communication systems

49. Disadvantage of underground system
over overhead system of power
distribution
1. More expensive
2. Difficult to locate the fault
3. Cannot be worked above 66kV due to
insulation difficulties