Hello,
While modelling a transmission line, I have considered L',R',C',G' are the inductance per unit length, resistance per unit length, capacitance per unit length and conductance per unit length respectively.
However, I don't know how does these parameters vary if the length of the transmission line is increased (say doubled).
Kindly clarify.
Thank you.
Hello Sanat ji,
There are some rules and equation for calculating Line L R C G. First of all determine the voltage of line as well as current you know there are several types of wire in the market including their business name and according to cataloger information per unit length of R is given. In case of L and C you have to count others parameters affecting LC in real time working. let suppose, for bundle conductor, the line capacitor and inductor becomes change with change of current and voltage.
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lets try it buddy
Best of luck
The answer is in the question. They are per unit length parameters and are independent of the length of the line.There are many texts on transmission lines that will explain the usenof these parameters.
Hi,
THis doesnot clarify my doubt. Let me put my question in this way. Suppose, I have my R, L, C, G for a 50m cable as 44 ohms, 1.5uH, 12nF and 50uS. Then what would be the effect on the values if I try to model a cable of length 100m.
I know that the resistance would for sure increase. What would be the effect on other values as I increase the cable length.
Would the L,C,G values increase or decrease_
Thank you.
from the basic formulae for parameters
R and L are directly proportional to the length.
C=(rho*e*area)/distance.
here the distance is not the length of the line. it is the distance between conductors or conductor to the earth depending on which capacitance you are calculating.
The area in the formula is directly proportional to the length. Keeping the other parameters constant, C is also directly proportional to the length of line.
When C increases, reactance decreases and hence a longer line draws more current compared to a shorter line.
So in short, all R,L and C are directly proportional to the length.
Dear Sanat,
In many text books, transmission line parameters are considered as per unit and per kilometer, so you should calculate the values yourself : (X= X(pu/km)* length(km)* Xbase).
In other word, transmission line parameters are directly proportional to the length.
Dear Sanat,
When we consider cable parameters per unit, this supposes that these parameters R' L', C' and G' do not depend on cable length. In other words, this supposes that, in a considered distance of the transmission line, the same cable type is used and distance between phases and distantance between cables and earth remain the same. In practice, this not really true but, it gives acceptable results.
The parameters increase with the increase in length of a cable/conductor
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