Terms Related to Performance of Transmission Line

Terms Related to Performance of Transmission Line

The voltage regulation and transmission efficiency are the most important terms while analysing the performance of transmission line.

i) Voltage regulation : Due to the current carried by the transmission line, it causes voltage drop in the line because of resistance and inductance associated with the line. As a result at the receiving end, the voltage is usually less than the voltage at the sending end. The drop in the voltage (V_S - V_R) of the line is expressed as a percentage of receiving end voltage V_R. This is called regulation.

The difference in voltage at the receiving end of the transmission line at the no load and full load is termed as voltage regulation expressed in terms of percentage of receiving end voltage.

Mathematically it is given as,

At no load there is no drop in the line and hence we have,

V_R = V_S

At full load, there is voltage drop in the line and the voltage is V_R.

% Voltage Regulation = V_S - V_R / V_R × 100

The voltage regulation of a transmission line should be as low as possible. With increase in load current, the change in receiving end voltage should be low.

ii) Transmission efficiency : There is always some power loss taking place in line resistance. Due to this power obtained at the receiving end of the line is usually less than that obtained at the sending end.

The ratio of power obtained at the receiving end to the power at sending end is called transmission efficiency of the line.

Mathematically we have

Review Question

1. Discuss the terms voltage regulation and transmission efficiency as applied to transmission line.

AU : May-17, Marks 4