Morderately long lines:

*Transmission lines between 80km and 240km can be assumed under this category.

*These transmission lines represented by T or π.

T-method

Vs=Sending end voltage for single phase

Vr=Receiving end voltage for single phase

Is=Sending end current

Ir=Receiving end current for single phase

Z=R+jX

Y=G+jB

G=leakage conductance per phase

B=Capacitive susceptance

π-method

Normally moderately long lines leakage may also be ignored. Therefore Y=G+jB=jwc0

W=Radian frequency of the power supply

C0=Capacitance to neutral of the transmission line.

Long lines:

*Te lines beyond 240km can be named as long lines.

*In Sri lanka, long lines cannot be seen yet!

*In long lines impedance & admittance assumed uniformly distributed.