Design and evaluation of a wind farm protection relay

The paper describes the design and evaluation of a protection relay for wind farms with fixed-speed induction generators. The relay provides short-circuit protection for a medium-voltage collection circuit and the medium-voltage (MV) and low-voltage (LV) windings of the generator-transformers connected to it. The ability to protect the generator-transformers allows a significant reduction in wind farm construction cost, since the MV fuses normally used to protect the generator-transformers are not required. The authors discuss how the operating characteristic for the protection was designed, implemented in a processor-based relay and then tested using a wind farm simulator and test set. A selection of test results are to illustrate how the relay performs occur on the protected collection LV terminals of a generator-transformers or on the utility network. The paper also discusses how the relay performed when installed at the Cemmaes wind farm in Wales for a 12 month site trial.