Zero Sequence Network for Transmission Line

To understand the meaning of zero sequence network of transmission system element consider a transmission line as element. If all three terminals of one end of transmission line are connected to same voltage source and other end terminals grounded current will flow through the transmission line and will complete return path through ground. If we consider equal spacing of conductor current through each conductor will be equivalent to V/Z. Where V is applied voltage. As voltage to each phase conductor of the line is same in magnitude as well as phase; applied voltage is now considered as zero sequence and impedance offered by line to this voltage is zero sequence impedance of the line. Normally zero sequence impedance of transmission line is 2.5 to 3 times its’ +Ve sequence impedance and the value and exact value is supplied by Corporate Office.