Transmission Line circuit representation .
Classification of transmission lines
Transmission lines are classified as :
1.Short,
2.Medium
3.Long.
Short transmission lines
When the length of the line is less than about 80Km the effect of shunt capacitance and conductance is neglected and the line is designated as a short transmission line. For these lines the operating voltage is less than 20KV.
Short Transmission LineThe equivalent circuit and vector diagram of a short transmission line are shown in the figure given below. In the equivalent circuit short transmission line is represented by the lumped parameters R and L. R is the resistance (per phase) L is the inductance (per phase) of the entire transmission line. As said earlier the effect of shunt capacitance and conductance is not considered in the equivalent circuit. The line is shown to have two ends: sending end (designated by the subscript S) at the generator, and the receiving end (designated R) at the load.
Medium transmission lines.
For medium transmission lines the length of the line is in between 80km - 240km and the operating line voltage wil be in between 21KV-100KV.In this case the shunt capacitance can be assumed to be lumped at the middle of the line or half of the shunt capacitance may be considered to be lumped each end of the line. The two representations of medium length lines are termed as nominal-T and nominal- π respectively.
long transmission lines.
Lines more than 240Km long and line voltage above 100KV require calculations in terms of distributed parameters. Such lines are known as long transmission lines. This classification on the basis of length is more or less arbitrary and the real criterion is the degree of accuracy required.
REFERENCE
No comments:
Post a Comment