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The power system network consists the following major
components:
 Generator
 Transmission line
 Distribution line
 Load
 Transformer
Generation: (Generator)
In generation the energy is converted from one form
to other forms and it voltage level be 6.6KV, 10.5KV,
11KV, 13.8KV and 15.75KV
Sending end substation: (Step up transformer)
The generated power can be transmitted by
increasing the voltage level to 110 KV, 132KV, 220KV,
400KV and 765KV, this stage is known as primary
transmission.
Receiving end substation: (Step down transformer)
In this stage the voltage level is reduced to 66KV,
33KV. This level is known as Secondary transmission.
Structure of Power System
Mr.C.Anandhakumar, AP / EEE, SRIT
6/14/2024
TRANSMISSION AND DISTRIBUTION

Receiving end substation: (Step down transformer)
In this stage the voltage level is reduced to 66KV, 33KV. This level is known as Secondary transmission.
Secondary substation: (Step down transformer)
In here the voltage level is reduced to 11KV, 6.6KV and 3.3KV. This level is known as Primary Distribution.
From this stage we can directly supply to the industries
Distribution station: (Step down transformer)
In here the voltage level is reduced to 440V, and 230V. This level is known as Secondary Distribution.
From this stage we can directly supply to the Commercial and Domestic loads.
Service Mains: (Distributed Transformer)
From here we can give supply to the various consumers.
The power system operation and planning can be done in by
 Load flow or Power flow Analysis
 Fault Analysis
 Stability Analysis
Structure of Power System Conti…
6/14/2024

Over Head and Underground Lines
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Parameter Overhead Lines Underground Cables
Conductor
For the overhead (transmission and
distribution) lines, the bare
conductor is used.
For underground (transmission and
distribution) cable, the insulated
conductor is used.
Conductor Size
The size of the conductor is smaller
as compared to the conductor of
the overhead cables.
The size of the conductor
is large due to the coated insulation.
Current
Capacity
The overhead line has a higher
current carrying capacity than the
underground cable.
The underground cable has a lesser
current carrying capacity as
compared to an overhead line.
Voltage Capacity
It carries a high voltage (near about
the 400kV).
It carries a limited voltage (not
more than 66kV).
Look You can easily visualize it.
As these cables are underground
you can not visualize them.

6/14/2024
Interference
Overhead lines interfere with
communication lines.
Underground cable does not
interfere with communication lines.
Insulation
It requires less insulation (only at
the contact point of the tower).
It requires more insulation (for
coating the whole conductor).
Outage Operation It requires low maintenance to
identify the outage location.
It requires high maintenance to
identify the outage location.
Cost The overhead line is cheaper.
The underground cable
is expensive.
Joint
Users can easily join the extra
connection on overhead lines.
Users can not easily join the extra
connection in underground cables.
Fault
Very easy to repair and clear the
fault.
Very difficult to repair and clear the
fault.

6/14/2024
Proximity effect
The proximity effect does not
affect overhead lines.
The proximity effect affects the
underground cables.
Corona effect
Corona effect finds in the
overhead system.
Corona effect does not find in the
underground system.
Environmental
Impact
It gets impacted by the
occurrences of environmental
attacks (like lightning,
windstorm, thunderstorm).
There are fewer chances of
environmental attacks in an underground
system.
Real time
Diagram

Need for EHV Transmission
 Increase in size of generating unit
 Increase in transmission efficiency
 Pithead steam plants and Remote hydro plants
 Number of circuits and land requirement
 Line costs
 Surge Impedance loading
EHVAC (Above 400KV to 765 KV)
6/14/2024
Volume
α
Cost
and
V
1
α
Volume 2
L
C
L
Impedance
Surge
Z
where
Z
V
P
C
C
2
RL
SIL




Merits of EHV Transmission
 Effect of high voltage on volume of copper and on efficiency.
 Reduction in the cost of conductor material for given power.
 From the above expression we conclude that if transmission voltage increase by n-times then
cost of the conductor reduces by 1/n2 times.
 Improvement in transmission efficiency.
 Reduction in percentage line drop. (Voltage increases then drop decreases)
 Improvement in voltage regulations
6/14/2024
φ
cos
V
1
Cost
Volume
Cost
that,
know
we
φ
cos
WV
ρl
3P
3al
required
conductor
of
Volume
2
2
L
2
2
L
2
2





Limitations of EHV Transmission
 More insulation is required for the conductor and tower.
 More clearance is required between the conductor and the ground.
 More Distance is required between the conductors. So the length of cross arms used is
increased.
 Extra care should be taken while designing the power equipments like transformer,
switchgears and others to handle such high voltage.
 Long or bulk power transmission is not possible (Due to High installation and maintenance
cost).
Demerits of EHV Transmission
 Corona loss and Radio interference.
 Line support cost.
6/14/2024

Demerits of EHV Transmission
 Erection difficulties.
 Insulation requirements.
 Power Station and substation equipments.
Environmental aspects in EHV Transmission
 Route clearance through country side and forests.
 Biological effects of electrostatic and electromagnetic fields.
 Audible noise.
 Ozone emission.
 Radio and television interference.
6/14/2024

EHV Transmission in Our Country
6/14/2024
400 KV Line
Dehar to Panipat Line
Obra to Sulanpur line
Sultanpur to Lucknow line
Obra to Kanpur line
Kanpur to Moradnagar line
Koradi to Katwa line
Srinagar to Jammu-Kashmir line
765 KV Line
Anpara to Unnao
Tehri to Meerut
Vindhayachal to Bina-Nagda
Kishanpur to Moga
Monubulu to Sriperumbudur
Agra to Gwalior
Pichor to Mainpur

HVDC
6/14/2024
Introduction:
After the advent of rectifiers and thyristors the HVDC become popular.
Simplified HVDC transmission system:
For Rectifier firing angle
Greater than 0 deg to less than 90 deg
For Inverter firing angle
Greater than 90 deg to less than 180 deg
HVDC Link classification:
 Mono polar Link
 Bi-polar link
 Homo polar link

HVDC
6/14/2024
HVDC Link:
 Mono polar link
 It uses only one conductor
 Return path may be provided by water or ground
 Economic
 Metallic return path may also be used where the earth resistance is too high
 Earthing of poles is done by earth electrodes, its located about 15 to 55 Km from the terminal stations.

HVDC
6/14/2024
HVDC Link:
 Bi - polar link
 It has two conductor. One for positive polarity and another one for Negative polarity.
 Set of converters are used in each line.
 The midpoint is earthed using line Electrodes and Earth Electrodes.
 The voltage range is 600KV, 500KV and 400KV (+- 5% is acceptable).
 If there is any fault occur in one side then, this system will acts as a monopolar system.
 The current flow through is always same.

HVDC
6/14/2024
HVDC Link:
 Homo - polar link
 It has two conductor. Both are Negative polarity.
 At present its not in use.
 Negative polarities are normally used to reduce the corona losses and radio interference.
 During faulty condition it will not acts as monopolar link.

Interconnection of HVDC to AC System
6/14/2024
 HVDC Bi-polar transmission system, where bulk power is transmitted from one point to another point
over long distance.
 Back – Back DC link.
 Parallel connections of AC and DC links.
 Multi Terminal DC links.
Applications of HVDC System:
 Long Distance bulk power transmission.
 Power transmission through underground or submarine cables.
 Asynchronous interconnections of AC system operating at different frequencies or where
independent control of system is desired.
 AC and DC lines in parallel.
 DC transmission with AC system.
 Back to back HVDC coupling stations
 Control and stabilization of power flow in AC

Limitations of HVDC System
6/14/2024
 High cost of conversion equipments
 Generation of harmonics which require AC and DC filters.
 Blocks the reactive power.
 Complexity of control.
HVDC links in INDIA:
765 KV Line
Rihand to Delhi (First DC in india and Largest in Asia) 810Km -Bi
Talcher to Kolar (1367 Km) – Bi
Chandrapur to Padghe 500KV - Bi
Hirma to Jaipur 600KV - Bi
Korba STPS to Karamsad 765 KV - Bi
Agra to Gwalior

Distribution System
6/14/2024
Introduction:
 Distribution is to deliver the power from generating stations and substations to various consumers.
 It consists of distribution transformer which step down the voltage from 11KV to 400 V for three and 230 V for
single phase supply.
Classification:
 According to supply
 DC Distribution
 AD Distribution
 According to Construction
 Over head System
 Under ground system
 According to Connection
 Radial System
 Ring Main System
 Interconnected System
 According to working
 Primary distribution
 Secondary distribution

Distribution System
6/14/2024
Major Components:
 Primary Distribution consists of feeders
 Radial feeder
 Simplest
 Economical
 Most commonly used one
 Used for supplying small and medium residential, commercial and industrial
 Radiates from secondary substation and branches into sub feeders
 Feeders and sub feeders uses three phase three wire system
 Laterals uses single phase
 Parallel feeder
 It consists of duplicate feed system shaving two radial feeders running in parallel
 Two feeders may originate from the same or different secondary substations.
 Each feeders supplies about half of the total load of the area,
 but has a capability to supply the entire load in the event.
 Loss of entire feeder will result in interruption of service until the load
normally supplied by the faulted feeder.
 Loop feeder or Ring Feeder
 Tow or more radial feeder originating from the same or different secondary substations
 It separately routed through the load areas is known as loop feeder system.
 If the ends of the two feeders are tied together through normally open switching
devices, the resulting arrangement is known as open loop feeder.
 If the ends of the two feeders are tied together through normally closed switching
devices, the resulting arrangement is known as ring loop or ring feeder.

Distribution System
6/14/2024
Major Components:
 Secondary Distribution components:
 Distributors are conductors from which current is tapped off for supply to the consumers.
 It uses 3-phase 4-wire systems 400V for 3-phase and 230 V for single phase.
 It laid along road sides
 The service connection to consumers are tapped off the distributors at convenient points.
 Service connections may be single – phase, 2-wire circuits or 3-phase 4-wire.
 Radial Distributors:
 If a distributor is connected to supply system from one end only, its called as
radial distributor.
 Disadvantages:
 Distributors nearest to the substation is heavily loaded.
 Due to load variation, voltage fluctuations is more at the far ends.
 If there is any fault occurs, there is no continuity of supply.
 Ring Main Distributor:
 A ring main distributor is arranged to form a closed loop.
 It may have one or more feeding points.
 It employs distributor which covers the whole area of supply finally retiring to the substation.
 Advantages:
 Due to load variations, the voltage fluctuation is less at the far end.
 Better Reliability.
 It gives continuity of supply, when fault occurs at any one distributor.

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Transmission and Distribution �ݺ�ߣ.pptx

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