The voltage
along transmission line depends upon
 Capacitive charging current and
 Loading of the Line
 The capacitance charging current depends upon capacitance between line and earth and its value depends upon geometry of the line.
 The capacitance generates reactive power and it is expressed in MVAr ( Here small ‘ r ‘ stands for reactive power )
Loading of the
line
 The load and line itself consumes reactive power.
Reactive Power
Generation in the Transmission Line

Reactive Power Absorb
in the Transmission Line

Capacitance between
transmission line and Ground

Transmission line
itself and load

Balance of
Reactive power
 It is necessary to balance generation and absorb of reactive power.
 The reactive power determines the voltage stability of the line whether it is overload lines or cable.
 If there is large amount of reactive power generation than absorb, the voltage will increase.
 If there is lack of reactive power, the voltage will decrease. Therefore the reactive power must be controlled for voltage stability.
Effect of Reactive Power

Effect

Reactive
Power Generation > Reactive Power Absorb

Voltage
Increases

Reactive
Power Generation < Reactive Power Absorb

Voltage
Decreases

Reactive
Power Generation = Reactive Power Absorb

Voltage
Stabilize

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