Parameters of a transmission lines|resistance|inductance|capacitance

 A transmission line is used to the transmit of electrical power from generating substation to the various distribution units. Transmission lines transmits the high voltage and current from one end to another. The transmission line is made up of a conductor of uniform cross-section along the line. Air work as an insulating medium or dielectric medium between the conductors.

For safety purpose, the distance between the line and ground is kept more. The electrical tower is used to give support to the conductors of the transmission line.Tower are made up of steel which provides high strength to the conductor. 

Parameters of transmission line

The performance of transmission line depends on the parameters of the transmission line. The transmission line has majorly four parameters -

 resistance

 inductance

 capacitance  

 shunt conductance. 

   These parameters are uniformly distributed along the line. Hence, also called the distributed parameter of the transmission line.

• Resistance : 

Resistance is the opposition of line conductors to current flow. Every material have the property to oppose the flow of current. The resistance is distributed uniformly along the whole length of the lines as  shown  in    figure. However , performance of a transmission line can be analysed conventionally if distributed resistance is considered as lumped as shown in figure.

• Inductance:

Electric power is transmitted through the transmission lines with alternating  high voltage and current . High  valued (AC) alternating current while flowing through conductor sets up alternating magnetic flux of high strength. This flux linkage with other adjecent conductors parallel to main conductor .                                                        The  inductance is also uniformly distributed along the length of conductor. 

• Capacitance: 

We know that any two conductors separated by insulating material constitute a capacitor.                                      

 As any two conductors of an overhead transmission lines are separated by air which acts as an insulation , therefore ,  capacitance exists between any two over- head line conductors . The capacitance between conductors is the change per unit potential difference.

The capacitance is uniformly distributed along the whole length of the line ( uniform series of capacitors connected between the conductors ). This results is that a current flows between the conductors known as charging current and flows in the line even it is open - circuited . 

These parameters affects the voltage drop along the line as well as the efficiency and power factor of the line.