Defining and Evaluating the Capacity Value of Distributed Generation

Installed capacities of distributed generation (DG) are projected to increase substantially in Great Britain and many other power systems. This paper will discuss the definition of capacity value of DG arising from its ability to support additional demand without the need for new network capacity, in analogy with the definition of effective load carrying capability (ELCC) at transmission level. This calculated ELCC depends on the precise detail of its definition; in particular in a demand group fed by a pair of circuits where the double outage state dominates the calculated reliability index, the ELCC will be very small unless the generator can run in islanded mode. Finally, requirements for use in practical planning studies and development of formal planning standards will be discussed.