Little attention has been paid to the development of control practices for utilities with power variations resulting from wind generation. One of the reasons is that little information is available on wind power variations from wind power arrays. This study demonstrates that severe operating problems can be caused by local storms in utilities with wind penetrations exceeding 5% of the utility's capacity. It is expected that future wind generation can comprise up to 15% of a utility's capacity which points to an even greater need for the development of control practices. The study was carried out by simulating wind power variations from various configurations of MOD-2 (with a capacity of 2 MW) wind turbine arrays during local storms. An existing wind data set collected at 27 meteorological measurement sites located in a square area of 128 km on a side was used to study the effects of spatial and temporal wind speed variations during storms. Wind power variations of individual units, arrays, and a series of multiple arrays are presented. It is shown that wind power variations of single arrays will be above 60% of capacity over a period of 15 min. Widely separated arrays reduce power variations but do not eliminate a high percentage of capacity changes in a 15-min period. Cyclic variation on a single unit due to turbulence is large as a percentage of capacity but does not produce large power variations as a percentage of multiple array power capacity.