Impact of reactive power transfer among transmission to distribution substations on the transmission network’s voltage

When power flows through a Distribution Network (DN), various physical phenomena occur, such as voltage drops and power losses. To minimize power losses of a DN, its topology can be modified by solving an optimization problem known as the Distribution Network Reconfiguration (DNR) problem. Variable Shunt Reactors (VSRs) can improve the voltage profile of the DN through the consumption of reactive power. DNs are interfaced with the Transmission Network (TN) through substations (SSs), and the two networks should operate in coordination. The research question that this paper tries to address is: suppose there is no overvoltage at a High Voltage (HV) bus1, but there is an overvoltage at another HV bus2, and that a VSR is initially connected to the HV bus1 through an SS. If a DNR is performed to transfer that VSR to HV bus 2, is there a TN where this procedure can, counterintuitively, increase the voltage at HV bus 2? An optimization is performed to investigate this question. From the results obtained through the simulations, a voltage rise of +1.42% was achieved. However, this value was obtained with unrealistic reactance-to-resistance ratios. By imposing constraints on the reactance-to-resistance ratios, no voltage rise was found.