The Study of Phase Shifting Transformer Control Angle Error Due to the Change of Its Reactance

This article describes the necessity of taking into account the changing reactance of a phase shifting transformer (PST), while calculating the control angle for different cases. It discusses various cases, such as forced redistribution of active power flows in electrical networks in order to reduce power losses, or ensuring specified loading of the lines. Constant values of PST reactance are used in studies, but this is not valid for all types of PST's. For some PST's, their reactance varies significantly, especially at large control angles, which may cause an error in calculation of the control angle. This paper investigates this phenomenon.