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Monday, 13 January 2020

Transmission Line Parameters, Skin Effect, Proximity Effect, Ferranti Effect, Transposition of Conductor.

Transmission Line Parameters 


  • The transmission line has different parameters and constant along with the length of line. 
  • Generally this parameters resistance, inductance, and capacitance. 
  • Such parameters affects on performance and efficiency of transmission line .
Transmission Line Parameters
Transmission Line Parameters


Concept of  R, L, and C in Transmission line 

Resistance 

It is opposition to flow of current in transmission line. The resistance is distributed along the length of line.

Inductance 

When ac current flow in the line change in flux occurs which links the conductor due to this flux leakage conductor passes as inductance. 

Capacitance 

When two conductors are separated by an insulating material then it called capacitance. As any two conductors of transmission line are separated which acts as insulation therefore capacitance exists between any two lines. 


Effect of Resistance in 

1) Transmission Line Efficiency

  • In case of transmission line receiving end power is always less than sending end power due to current losses and voltage drop occurs in line hence we get less power at receiving ends. 
2) Voltage Regulation
  • Voltage regulation is defined as the ration of change in voltage at sending end to receiving end or from no load to full load.
  • Because of line parameters receiving end voltage is always less than sending end voltage.


Effect of Inductance 

Skin Effect 
  • The tenancy of alternating current to concentrate near the conductor is known as skin effect.
  • Due to the skin effect the effective area of cross section of conductor through which current flow is reduce therefore the resistance of conductor is slightly increases when ac current flows.
  • A solid conductor when used for transmission current is flow through all the parts i.e inner filament of conductor. Therefore flux linkage takes place at center. There is more effect of magnetic flux and hence have larger inductance than surface of conductor.
  • If we move from center towards the surface the effect of inductance goes decreases and due to this current flows near the surfaces of conductor only.
  • This crowding of  current near conductor surface is skin effect.
  • It depends on 
1) Nature of material
2) Diameter of conductor
3)Supply frequency
4)Shape of conductor 

Proximity Effect
Proximity Effect
Proximity Effect 


  • Suppose the conductor of transmission line are separated by certain distance. When the conductor carries current then the flux is link with another conductor i.e there will be flux linkage of both conductors.
  • When conductor A carries current its flux will link conductor B. If both are conductors carries current in opposite direction due to its flux linkage the current through both the conductors will try to flow only for shaded portion of  conductor.
  • If both conductors carries current in same direction due to its flux linkage current will only flow outer cross sectional area of  conductor. This effect is known as proximity effect.
  • It can be reduced by increasing distance between two conductors and reducing current flow through conductors.

Ferranti effect

Ferranti Effect
Ferranti Effect

  • When along with transmission line is operated under no load or light load condition then receiving end voltage is greater than sending end voltage. 
  • Due to capacitive reactance of the system current flowing through to line is in leading PF this charging current produces voltage drop in reactance which in phase opposition to receiving end voltage hence vr^vs this effect is known as ferranti effect.
Transposition of conductor

Transposition Of Conductor
Transposition Of Conductor
When three phase line conductors are not equidistant from each other the conductor spacing is
said to be unsymmetrical under such Condition flux linkage and inductance of each phase are
not same.The different inductance in each phase result in unequal voltage drop  in 3 phase. Even
though the current in the conductor in three phase are equal. Therefore the VR will not be same
for all phases in order that voltage drop are equal in all conductors. we generally interchange the
position of conductor at regular interval along the length of lines of that each conductor take
original position of another conductor over equal distance such an exchange of position is

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