MOSFET as a Switch
Relationship of Line and Phase Voltages and Currents in a Star Connected System
555 Timer and 555 Timer Working
Corona Effect in Power System
Ferranti Effect in Power System
Advantages of Three Phase System over Single Phase System
Inductance in Single Conductor Power Transmission Line
Inductance in Three Phase Transmission Line
Why Supply Frequency 50 or 60 Hz not Other Values than these?
Power System Stability
Load Flow or Power Flow Analysis
Transient Stability in Power System
Flexible AC Transmission Systems (FACTS)
Tariff of electricity in India
Power Factor | Calculation and Power Factor Improvement
Skin Effect in Transmission Lines
Inductance of Two Wire Single Phase Transmission Line
Electrical Power Cable
Types of Overhead Conductor
Testing of Electrical Power Cable | Type Test | Acceptance Test | Routine Test
Conductor Resistance Test of Electrical Power Cables
Test for Thickness of Insulation of Power Cable
Annealing Test for Wires and Conductors
Tensile Test of Conductors
Persulphate Test of Conductor
Wrapping Test for Conductors
Capacitor Bank | Reactive Power Compensation
Types of Capacitor Bank
Specifications or Rating of Power Capacitor Bank
Switchable Capacitor Bank or Switched Capacitor Bank
Location of Shunt Capacitors
Electrical Insulator | Insulating Material | Porcelain Glass Polymer Insulator
Types of Electrical Insulator | Overhead Insulator
Insulation Coordination in Power System
Electrical Insulator Testing | Cause of Insulator failure
Electrical Power Substation Engineering and Layout
Electrical Bus System and Electrical Substation Layout
Mobile Substation | Portable Substation | Mobile Transformer
Load Curve | Load Duration Curve | Daily Load Curve
Electrical Transmission Tower Types and Design
Methods of Transmission Tower Erection
Basic Concept of Transmission Tower Foundation
Design of Foundations of Transmission Towers in different Soils
Electrical Power Transmission System and Network
Transmission Line in Power System
Voltage in Power Electric Lines
Short Transmission Line
Medium Transmission Line
Long Transmission Line
Performance of Transmission Line
ABCD Parameters of Transmission Line
Sag in Overhead Conductor
Skin Effect in Transmission Lines
Skin EffectThe phenomena arising due to unequal distribution of current over the entire cross section of the conductor being used for long distance power transmission is referred as the skin effect in transmission lines. Such a phenomena does not have much role to play in case of a very short line, but with increase in the effective length of the conductors, skin effect increases considerably. So the modifications in line calculation needs to be done accordingly. The distribution of current over the entire cross section of the conductor is quite uniform in case of a DC system. But what we are using in the present era of power system engineering is predominantly an alternating current system, where the current tends to flow with higher density through the surface of the conductors (i.e skin of the conductor), leaving the core deprived of necessary number of electrons.
In fact there even arises a condition when absolutely no current flows through the core, and concentrating the entire amount on the surface region, thus resulting in an increase in the effective electrical resistance of the conductor. This particular trend of an AC transmission system to take the surface path for the flow of current depriving the core is referred to as the skin effect in transmission lines.
Why Skin Effect Occurs in Transmission Lines?Having understood the phenomena of skin effect let us now see why this arises in case of an AC system. To have a clear understanding of that look into the cross sectional view of the conductor during the flow of alternating current given in the diagram below. Let us initially consider the solid conductor to be split up into a number of annular filaments spaced infinitely small distance apart, such that each filament carries an infinitely small fraction of the total current. Like if the total current = I Lets consider the conductor to be split up into n filament carrying current ‘i’ such that I = n i. Now during the flow of an alternating current, the current carrying filaments lying on the core has a flux linkage with the entire conductor cross section including the filaments of the surface as well as those in the core. Whereas the flux set up by the outer filaments is restricted only to the surface itself and is unable to link with the inner filaments.Thus the flux linkage of the conductor increases as we move closer towards the core and at the same rate increases the inductor as it has a direct proportionality relationship with flux linkage. This results in a larger inductive reactance being induced into the core as compared to the outer sections of the conductor. The high value of reactance in the inner section results in the current being distributed in an un-uniform manner and forcing the bulk of the current to flow through the outer surface or skin giving rise to the phenomena called skin effect in transmission lines.
Factors Affecting Skin Effect in Transmission LinesThe skin effect in an ac system depends on a number of factors like:-
- Shape of conductor.
- Type of material.
- Diameter of the conductors.
- Operational frequency.