A new approach for the calculation of disturbing currents in inductively coupled transmission lines

In this paper the authors present measurements, calculations and results of the optimization of transposition schemes and phase configurations of transmission lines in a region in Austria regarding inductively coupled transmission lines. Different development states of the power circuit and variants under economic and realizable practical conditions are presented. The calculations were performed with a new calculation method combining the node potential method and a chain-ladder model for coupled line conductors to calculate the inductive influence and unbalance currents (zero-sequence currents) of extended transmission line circuits in normal operation mode. The presented method allows the calculation of unbalance currents and the effects of inductive coupling for a given network scenario with a coupled transmission line model. The investigation of these disturbance currents lead to an optimized transposition scheme considering economic aspects (reduced number of transposition towers at predefined places, small zero-sequence currents, etc.). With this method existing grids can be optimized by reducing circulating currents. Also extension strategies and decisions for the integration of new transformer substations and different grid configurations can be provided.