Performance & Characteristics of Transmission Lines
Demonstrative Video
Overview
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
Objectives of this Chapter
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
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:
\[\begin{aligned} z &= \text{series impedance per unit length per phase}\\ y &= \text{shunt admittance per unit length per phase to neutral}\\ l &= \text{length of the line}\\ Z &= zl = \text{total series impedance per phase}\\ Y &= yl = \text{total shunt admittance per phase to neutral} \end{aligned}\]
Relation between Sending end & Receiving end Quantities
$$\boxed{ \left[\begin{array}{c} V_S \\ I_S \end{array}\right]=\left[\begin{array}{ll} A & B \\ C & D \end{array}\right]\left[\begin{array}{l} V_R \\ I_R \end{array}\right] \Longrightarrow\left[\begin{array}{l} V_R \\ I_R \end{array}\right]=\left[\begin{array}{cc} D & -B \\ -C & A \end{array}\right]\left[\begin{array}{c} V_S \\ I_S \end{array}\right] }$$
Characteristics & Performance of Transmission Lines
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 \[\dfrac{\text{No load receiving end voltage - F.L. receiving end voltage}}{\text{F.L. receiving end voltage}} \times 100\%\]