Lecture-16: Performance & Characteristics of TL

Lecture-17: Short Transmission Line

Lecture-18: Medium Transmission Line

Lecture-19: Long Transmission Line

Lecture-20: Surge Impedance Loading

Lecture-21: Ferranti Effect

Lecture-22: Tuned Power Lines

Lecture-23: Equivalent Circuit of Long TL

Objective:

Develop formulas to calculate the voltage, current, and power at any point on the T/L, provided we know the values at one point, usually at one end of the line.

To understand the effects of parameters of the line on bus voltages and the flow of power.

Introduction to the study of transients on lossless lines in order to indicate how problems arise due to surges caused by lightning and switching.

Representation of Line:

SHORT LINE: less than 80 Kms : capacitance neglected

MEDIUM LINE: 80-240 Kms

LONG LINE: longer than 240 Kms

For short and medium line: lumped parameters are used

Long line: Distributed parameters are used

Normally, TL are operated with balanced 3-\(\Phi\) load

Nomenclatures used:

\[\begin{aligned} z &= \text{series impedance per unit length per phase}\\ y &= \text{shunt admittance per unit length per phase to neutral}\\ l &= \text{length of the line}\\ Z &= zl = \text{total series impedance per phase}\\ Y &= yl = \text{total shunt admittance per phase to neutral} \end{aligned}\]

$$\boxed{ \left[\begin{array}{c} V_S \\ I_S \end{array}\right]=\left[\begin{array}{ll} A & B \\ C & D \end{array}\right]\left[\begin{array}{l} V_R \\ I_R \end{array}\right] \Longrightarrow\left[\begin{array}{l} V_R \\ I_R \end{array}\right]=\left[\begin{array}{cc} D & -B \\ -C & A \end{array}\right]\left[\begin{array}{c} V_S \\ I_S \end{array}\right] }$$

Power delivered at receiving end \[= \text{Power sent from sending end} - \text{Line losses}\]

Efficiency of TL \[\dfrac{\text{Power delivered at receiving end}}{\text{Power sent from sending end}} \times 100\%\]

% Regulation \[\dfrac{\text{No load receiving end voltage - F.L. receiving end voltage}}{\text{F.L. receiving end voltage}} \times 100\%\]