introduction to power system

Evolution of Electric Power Systems
 An electric power system is a network of electrical
components deployed to supply, transfer, store, and use
electric power
 The first complete electric power system was built by
Thomas Edison- the historic Pearl Street Station in New
York City which began operation in September 1882.
• Comprising a generator, cable, fuse, meter and loads.
• It was dc system:-steam engine driven dc generator
• 59 customers in 1.5 km radius
• Load: incandescent lamps
• Underground cable system, 110 v.
2

Cont’d…
Within a few years similar systems were in operation
in most large cities throughout the world.
With the development of motors by Frank Sprague in
1884, motor loads were added to such systems.
By 1886, the limitations of dc systems were becoming
increasingly apparent. They could deliver power only a
short distance from the generators.
3

Cont’d…
L. Gaulard and J.D. Gibbs of Paris, France developed
transformer and ac transmission.
In 1886, William Stanley developed and tested a
commercially practical transformer and ac distribution
system for 150 lamps at Great Barrington,
Massachusetts.
In 1889, the first ac transmission line in North America
was put in to operation. It was a single phase line
transmitting power at 4,000 V over a distance of 21 km.
4

Cont’d…
With the development of poly phase systems by Nikola
Tesla, the ac system became even more attractive.
In the 1890s, there was considerable controversy over
whether the electric utility industry should be
standardized on dc or ac.
There were passionate arguments between Edison,
who advocate dc, and Nikola Tesla, who favored ac.
5

Cont’d…
By the turn of the century, the ac system had won out
over the dc system for the following reasons:
• Voltage levels can be easily transformed in ac
systems, thus providing the flexibility for use of
different voltages for generation, transmission and
consumption.
• AC generators are much simpler than dc generators.
• AC motors are much simpler and cheaper than dc
motors.
6

Cont’d…
The first three phase line in North America went in to
operation in 1893 , a 2300V, 12km line.
In the early period of ac power transmission, frequency
was not standardized.
Many different frequencies were in use: 25, 50, 60, 125
and 133 Hz.
60 Hz was adopted as standard in North America and
many other countries use 50 Hz.
7

Cont’d…
The increasing need for transmitting larger amounts of
power over longer distances created an incentive to use
progressively higher voltage levels.
To avoid the proliferation of an unlimited number of
voltages, the industry has standardized voltage levels.
With the development of mercury arc valves in the early
1950s, high voltage dc (HVDC) transmission systems
became economical in special situations.
The cross over point beyond which dc transmission may
become a competitive alternative to ac transmission is
around 500 km for over head lines and 50 km for
underground or submarine cables.
8

Cont’d…
HVDC transmission also provides an asynchronous
link between systems where ac interconnection would
be impractical because of system stability
considerations or because nominal frequencies of the
systems are different.
The first modern commercial application of HVDC
transmission occurred in 1954 when the Swedish
mainland and the island of Gotland were
interconnected by a 96 km submarine cable.

9

Cont’d…
With the advent of thyristor valve converters, HVDC
transmission became even more attractive.
The first application of an HVDC system using
thyristor valves was at Eel River in 1972.
With the cost and size of conversion equipment
decreasing and its reliability increasing, there has been
a steady increase in the use of HVDC transmission.
10

Sources of Energy
The major sources of primary energy are:
 Fossil fuels: coal, natural gas and oil
 Water power: Hydroelectric power
 Nuclear power: fission and fusion
 Solar energy: heat radiation from the sun
 Geothermal energy: thermal springs due to inner
strata of earth at a very high temperature
 Wind power: wind turbines
 Tidal power: tides of ocean
11

Cont’d…
 Share of global electricity
12

Cont’d…
 Fossil fuel thermal power plant
13

Cont’d…
 Cross-section of a fossil fuel-fired thermal power plant
14

Cont’d…
 Hydro-electric power plant
15
Gilgel Gibe III Dam

Cont’d…
 Cross-section of a hydro-electric power plant
16

Cont’d…
 Cross-section of a nuclear power plant
18

Cont’d…
 Wind power plant
19

Cont’d…
 Geothermal power plant
21

Cont’d…
 Tidal power plant
23

AC and DC transmission
Comparison of AC and DC Transmission
Electric Power can either be transmitted by means of AC or DC
Advantages of DC Transmission:
• Power transmission by means of DC requires only two
conductors as compared to three conductors required for AC.
• There is no inductance, capacitance, phase displacement and
surge problem in DC transmission.
• Due to absence of inductance, the voltage drop in DC
transmission is less than the AC transmission for same load
and receiving end voltage.
• A DC transmission line has less Corona and hence efficiency is
improved.
• In DC transmission, there is no stability and synchronization
problem.
24

Cont’d…
Disadvantages of DC Transmission:
 DC Power generation is difficult due to commutation
problem.
 Transformer does not work for DC and therefore
voltage level of DC cannot be changed for power
transmission.
 DC Switches and Circuit Breakers have their own
limitations
25

Cont’d…
Advantages of AC Transmission:
 AC power can be generated at high voltage. The maximum
voltage at which Electrical Power is generated in India is at 21 kV.
 AC voltage can be stepped up for power transmission at high
voltage.
Disadvantages of DC Transmission:
 AC transmission requires more conductor material as compared
to DC transmission.
 The construction of AC transmission line is more complicated as
compared to DC transmission line.
 Due to Skin Effect in AC transmission, the effective resistance of
conductor increases.
26

Cont’d…
27
Cost comparison of HVDC and HVAC overhead transmission lines

3 phase vs Single phase systems
Advantages of a three phase system over a single phase
power system
 The rating, i.e. the output of a three-phase machine is
nearly 1.5 times the rating (output) of a single phase
machine of the same size
 In single phase circuits, the power delivered is pulsating.
Whereas, in the polyphase system, the power delivered is
almost constant when the loads are in balanced condition
 Single Phase induction motors are not self starting as it
does not have starting torque, where as Three phase
induction motors are self starting.
 3 Phase system requires less copper and aluminium for the
transmission system in comparison to a single phase
transmission system.
28

Cont’d…
 In 3 phase motor, the frequency of vibrations is less as
compared to single phase motor because in single phase
the power transferred is a function of current and varies
constantly
 3 Phase system requires less copper and aluminium for the
transmission system in comparison to a single phase
transmission system.
Disadvantages of 3 phase system over single phase
 Unbalanced loading ( can cause voltage fluctuations )
 Complex System (requires symmetrical components for
analysis and operation )
 Phase Sequence needed to be kept in mind while making
connections
29

Structure of the Power System
Electrical systems vary in size and structural
components.
However, they all have the same basic
characteristics.
 Generation system
 Transmission system
 Sub-transmission system
 Distribution system
30

introduction to power system

More Related Content

What's hot (20)

Similar to introduction to power system (20)

Recently uploaded (20)

introduction to power system