The performance of a power system is mainly dependent on the performance of the transmission lines in the system.It is necessary to calculate the voltage,current and power at any point on a transmission line provided the values at one point are known.
The transmission line performance is governed by its four parameters - series resistance and inductance,shunt capacitance and conductance.All these parameters are distributed over the length of the line.The insulation of a line is seldom perfect and leakage currents flow over the surface of insulators especially during bad weather.This leakage is simulated by shunt conductance.The shunt conductance is in parallel with the system capacitance.Generally the leakage currents are small and the shunt conductance is ignored in calculations.
Performance of transmission lines is meant the determination of efficiency and regulation of lines.The efficiency of transmission lines is defined as
The end of the line where load is connected is called the receiving end and where source of supply is connected is called the sending end.
The Regulation of a line is defined as the change in the receiving end voltage, expressed in percent of full load voltage, from no load to full load, keeping the sending end voltage and frequency constant.