The presentation is delivering the general aspects of transmission of electric energy. At the beginning need of transmission is presented, and then the various aspects of transmission, which affect the choice of scheme of transmission are presented. At the end of presentation, the topic is summarized as comparison among the HVAC and HVDC transmission. This presentation was given by shivlal mohal, during the final semester of electric engineering.

1. CLG INSTITUTE OF ENGINEERING
AND TECHNOLOGY, SUMERPUR
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Presented by: Shivlal Mohal
(8th sem,Electrical department)

2. HIGH VOLTAGE TRANSMISSION
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3. OUTLINE:
• Transmission
– Definition
– Need of transmission
• Aspects of transmission
– Voltage level for transmission of electric power
– Corona loss
– Skin effect
– Sheath losses
– Problem of synchronizing
– Effective impedance of line
– Effective Impedance of the line
– Loss of power in conversion
• Break even distance
• Relative comparison of HVDC and HVAC
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4. TRANSMISSION
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5. DEFINITION
• Transmitting the generated power from power
station to the load centers, for utilization.
• The load centers are located far away from the
power stations.
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6. NEED OF TRANSMISSION
1. Decentralization of load centers
2. Scale of economy
3. Environmental effects
4. Availability of resources
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7. ASPECTS OF TRANSMISSION
Voltage level for transmission of electric power:
The voltage level can be made to vary easily by
transformer action easily in case of AC.
Try is made to transmitting the power at
maximum possible transmission voltage,
because of : H=I²RT
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8. Power loss= .00241[(f+25)/$]*[root of (r/d)]*square
of[Vp-Vo]
f= supply frequency
$= air density correction factor
Vp = operating voltage
Vo= critical disprutive voltage
r= radius of conductor
d= distance of separation for fine weather
CORONA LOSS
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CORONA LOSS

10. -Higher density of current of at outermost area at high
frequencies.
SKIN EFFECT
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11. The skin effect opposes the flow of
current at the center of the conductor,
which increases the resultant Impedance
of the line.
This also produces difficulties for
underground lines.
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SKIN EFFECT

12. SHEATH LOSSES (IN UNDERGROUND
CABLES)
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13. PROBLEM OF SYNCHRONIZING
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14. The effective impedance of line for a HVAC line is given
as:
EFFECTIVE IMPEDANCE OF THE LINE
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15. • As in HVDC transmission the conversion is required
at both the ends, therefore the conversion losses in
HVDC transmission is more compared to HVAC
transmission.
LOSS OF POWER IN CONVERSION
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16. BREAK EVEN DISTANCE
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17. RELATIVE COMPARISON OF
HVAC AND HVDC
HVAC
• Corona losses are more because of
higher frequencies.
• Skin effect is more because of higher
frequencies.
• Sheath losses are function of
frequency, therefore will appear more
in HVAC.
• Problem of synchronizing is of very
importance.
• Economical up to distance : 800 to
1000 kilometers.
HVDC
• Corona losses are less because of
higher DC has zero frequency.
• Compared HVAC Skin effect in
HVDC is very less.
• Sheath losses are function of
frequency, therefore will appear less
in HVDC.
• Problem of synchronizing do not have
that much important.
• Economical up to distance : onwards
1000 kilometers.
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18. HVAC
• Number of conductors required : 3
conductor at as in general practice.
• Effective Impedance of the line :
Contributed by capacitance,
inductance, resistance.
• Loss of power in conversion : If
transmitted by HVAC, requires no
conversion, therefore conversion
losses are negligible.
HVDC
• Number of conductors required : 2
conductors are enough.
• Effective Impedance of Contributed
by resistance.
• Loss of power in conversion : If
transmitted by HVDC, requires
conversion at both ends, therefore
conversion losses are more.
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