11 Distribution System and Distributed Energy Resources

Having considered electricity consumers and their choices behind their meters, we turn to innovation within electric distribution systems. As discussed in Chapter 7, the vast majority of electric distribution systems, whether IOU or POU owned, are radial flow from substations where high voltage, from 765 kV to 138 kV, used for transmission is stepped down for delivery to electric customers at voltages ranging from 138 kV for very large customers, to 69 kV for large customers, to as low as 120 V for delivery to individual households.