What is transmission Line? Transmission line is the long conductor with special design (bundled) to carry bulk amount of generated p...
What is transmission Line?
Transmission line is the long conductor with special design (bundled) to carry bulk amount of generated power at very high voltage from one station to another as per variation of the voltage level.
Type of transmission Line
In transmission line determination of voltage drop, transmission efficiency, line loss etc. are important things to design. These values are affected by line parameter R, L and C of the transmission line. Length wise transmission lines are three types.
Short Transmission Line
 Length is about 50 km.
 Voltage level is up to 20 kV
 Capacitance effect is negligible
 Only resistance and inductance are taken in calculation capacitance is neglected.
Medium Transmission Line
 Length is about 50km to 150km
 Operational voltage level is from 20 kV to 100 kV
 Capacitance effect is present
 Distributed capacitance form is used for calculation purpose.
Long Transmission Line
 Length is more than 150 km
 Voltage level is above 100 kV
 Line constants are considered as distributed over the length of the line.
What is the Transmission Efficiency?
Transmission efficiency is defined as the ration of receiving end power P_{R} to the sending end power P_{S} and it is expressed in percentage value.
cosÎ¸_{s} is the sending end power factor.
cosÎ¸_{R} is the receiving end power factor.
V_{s} is the sending end voltage per phase.
V_{R} is the receiving end voltage per phase.
What is Transmission Line Voltage Regulation
Voltage regulation of transmission line is defined as the ratio of difference between sending and receiving end voltage to receiving end voltage of a transmission line between conditions of no load and full load. It is also expressed in percentage.
Where V_{s} is the sending end voltage per phase and V_{R} is the receiving end voltage per phase.
X_{L} is the reactance per phase.
R is the resistance per phase.
cosÎ¸_{R} is the receiving end power factor.
Effect of load power factor on regulation of transmission line:

For lagging load

For leading load
Now
 Power factor is lagging or unity, and then VR is increased and goes to be positive.
 Power factor is leading, and then VR is decreased and goes to be negative.
For lagging load
For leading load
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