SYSTEM FOR FREQUENCY REGULATION ON A POWER DISTRIBUTION NETWORK

System for controlling voltage supply to a portion of a distribution grid, the portion of the grid including a substation providing one or more circuit element operable to increase or decrease the voltage supplied to consumers within the portion of the grid. Data set includes a previously measured power consumption associated with previously measured values of at least one property for a portion of the grid. Measurement device measures the at least one property supplied within the portion of the grid. Processing device determines from the previously measured values of the at least one property in the data set an effect of altering the value of the at least one property from a first value to a second value, on the power consumption of those consumers.