Analysis of current unbalance in meshed transmission system

Abstract

The paper describes new approach of the calculation of current unbalance in a meshed transmission system. The system is composed of several parts with different types of towers, phase sequence arrangements, types of conductors and one or two transmission lines on the same tower. The calculations are performed by dividing the problem to a number of impedance matrices respecting the mutual impedances between all conductors. In the examined transmission system there exist parts with different number of lines but the same number of shield wires. For connection of parts with two transmission lines and two shield wires to another part with one transmission line and two shield wires, virtual shield wires must be created to keep the continuity of the calculations. After current unbalance calculations, necessary steps must be taken to symmetrize the part of the transmission system examined. Due to requirement of changing phase sequence arrangement only in one part of our system, classical way of transposition based on line division into three parts and alternation of conductors between themselves cannot be used. All possible phase sequence arrangements in each transmission line of the part of the system are examined, the best solution must be then calculated and selected.