Method to measure the unbalance of the multiple-circuit transmission lines on the same tower and its applications

This study proposes a new method for measuring the unbalance of the multiple-circuit transmission lines (MCTLs) on the same tower, which can characterise the physical natures of the line unbalance. First, the impedance and the sequence current of the MCTLs on the same tower are calculated under the consideration of the impact of ground wires. Then, the unbalance suppression methods of the optimal phase sequence arrangement and asymmetry parameter compensation are presented. Finally, the model of the six-circuit transmission lines on the same tower is simulated in PSCAD according to a real project in China. The line unbalance, the impacts of the connection patterns of ground wires on unbalance and the unbalance suppression are simulated and analysed. Simulation results show that the proposed method is applicable and convenient to accurately calculate the parameters of the line unbalance and to select the optimal way to suppress the unbalance. The work can provide the theoretical guidance for the optimal design and the operation of the MCTLs on the same tower.