Protecting grid connected wind farms

The investment in wind farms is increasing rapidly and in many aspects the industry is maturing. Instead of connecting single wind turbine or small wind farms to the distribution network, the energy companies and manufactures are connecting large wind farms to the transmission network. These farms can contain 200 plus turbines and have a rated capacity of greater than 500 MW up to several GW. Providing proper protection for these farms is a major challenge. In the UK, any wind farm rated above 100 MW is required to obey the grid code which means the protection consideration will be directed for grid connection and will be different from wind farms which are connected to the distribution network. In addition to the considerations of a grid connected generator, the particular characteristics of the types of turbine involved add further complications. This paper reviews the existing technologies used for protecting large wind farms and how they will affect the protection of the local transmission feeders and busbars. It is a challenge for the wind farm's protection to achieve 120 ms fault clearance for the transmission network and 800 ms fir a back up protection. Since wind turbines have different characteristics to those of conventional power plant, the paper discusses the special features and settings for the protection schemes used for large wind farms.