The global voltage regulation: a suggested measure for the supply quality in distribution networks

Abstract Based on closed form expressions for the power frequency voltages and currents in a typical radial distribution network, the voltage regulation VR at any time point during the day could be evaluated. It will depend primarily on the network configuration, the daily load curve, the load density and its power factor as well as the level of eventual reactive power compensation. The root mean square (RMS) value of the voltage regulation, VRrms(t), computed at a certain time t, can give a useful indicator for the voltage constancy over the network at that time point. The concept of the “Global Voltage Regulation” (GVR) is introduced. The GVR is defined as the root mean square (RMS) value of the voltage regulation, VRrms(t), over the day time, as t varies from 0 to 24 h. Accordingly, it takes into account the effect of both the geometrical dimensions of the distribution network and the daily temporal variation of the voltage regulation. The theoretical value GVR=0 corresponds to the ideal case in which the voltage is constant at all nodes, all the time. Hence, the GVR can be considered as a representative figure of merit describing the supply quality regarding the voltage values prevailing at the different network nodes, all over the day. The paper addresses also the identification of the optimal level of reactive power compensation k that will lead to the least possible GVR. Moreover, the impact of both the network and load parameters on the optimal value of k is investigated. The results of several parameter studies are presented and discussed.