Abstract
This paper reviews the present purpose and functioning of grid codes for the proper operation of ‘national’ power networks. Now that embedded generation, including especially windfarms, may have total capacities large enough to compare with previous central generating plant, the grid codes are being changed to accommodate such generation. Modern wind turbines need to operate under new and challenging constraints that require the introduction of both new technology and sympathetic grid regimes. The most important characteristics affecting both the grid and the turbines are examined. It is concluded that modern wind turbines can generally be designed to support the maintenance of grid supply, frequency and voltage more effectively than present central plant. However, the manner in which that is achieved needs to be different in many respects from current codes that were developed around the characteristics of central and conventional plant. Indications of the necessary changes in grid codes are given.