Reactive Power Compensation in Present MV and LV Grids: The Approach of SET Distribuzione

In recent years, several factors, including the conversion of overhead feeders into cable lines and the spread of power electronics, have contributed to a significant change in the nature of distribution networks' loading. In the past, network equivalent capacitance was largely compensated by ohmic-inductive loads. Conversely, today most of the network operated by SET Distribuzione experiences an ohmic-capacitive behavior even when loaded, leading to undesired inductive power injections into the High Voltage National Transmission Grid. In this regard the present paper illustrates the compensation approach devised and implemented by SET Distribuzione. It consists in a combination of distributed shunt reactors to locally compensate the capacitive power absorption of cable branches and loads. Shunt reactors are installed either at the Medium Voltage side or at the Low Voltage side of some Secondary Substations. Simulations and field experience have proved this solution to be effective in providing valuable local reactive compensation, together with an improvement in voltage profile regulation and a remarkable reduction in the loading of feeder branches, with benefits in terms of network distribution losses.