# Performance of Transmission Lines

## Performance of Transmission Lines:

Circuit Constants of a Transmission Line : In any four terminal network, the input voltage and input current can be expressed in terms of output voltage and output current. Incidentally, a Circuit Constants of a Transmission Line is a 4-terminal network ; two input terminals where power enters the network and two output terminals where power leaves the network. Therefore, the input voltage (VS) and input current (IS) of a 3-phase …

Classification of Overhead Transmission Lines : The important considerations in the design, operation and Classification of Overhead Transmission Lines are the determination of voltage drop, line losses and efficiency of transmission. These values are greatly influenced by the line constants R,L and C of the transmission line. For instance, the voltage drop in the line depends upon the values of above three line constants. Similarly, the resistance of transmission line …

Long Transmission Line Voltage : It is well known that line constants of the transmission line are uniformly distributed over the entire length of the line. However, reasonable accuracy can be obtained in line calculations for short and medium lines by considering these constants as lumped. If such an assumption of lumped constants is applied to Long Transmission Line Voltage (having length excess of about 150 km), it is found …

Medium Transmission Line Voltage : In short transmission line calculations; the effects attic line capacitance are neglected because such lines have smaller lengths and transmit power at relatively low voltages (<20 kV): However, as the length and voltage of the line increase, the capacitance gradually becomes of greater importance. Since Medium Transmission Line Voltage have sufficient length (50-150 km) and usually operate at voltages greater than 20 kV, the effects …

Performance of Single Phase Short Transmission Line Voltage : As stated earlier, the effects of line capacitance are neglected for a short transmission line. Therefore, while studying the performance of such a line, only resistance and inductance of the line are taken into account. The equivalent circuit of a Single Phase Short Transmission Line Voltage is shown in Fig. 10.1 (i). Here, the total line resistance and inductance are shown …

Performance of Three Phase Short Transmission Line : For reasons associated with economy, transmission of electric power is done by Three Phase Short Transmission Line. This system may be regarded as consisting of three single Phase units, each wire transmitting one-third of the total power. As a matter of convenience, we generally analyse 3-phase system by considering one phase only. Therefore, expression for regulation, efficiency etc. derived for a single phase line …