Design and field testing of a source based protection relay for wind farms

The paper describes the design and field testing of a source based relay suitable for the protection of wind farms with fixed-speed induction generators. The relay provides short-circuit protection for the medium voltage (MV) power collection circuit and the MV and low voltage (LV) windings of each generator transformer. The use of the relay allows a reduction in the construction cost of a wind farm, since MV fuses are no longer required to protect the generator transformers. The paper discusses how the protection algorithm was designed based on the electrical behaviour of induction generators operating in a wind farm. The relay was evaluated at a wind farm in Wales and also in the laboratory using data from a wind farm simulator and a transient recorder. The latter, installed at the wind farm, recorded the voltage and current signals measured during local disturbances. The recorded or simulated data was subsequently replayed into a relay simulator which graphically describes the operating behaviour of the protection.