Research Of Three Winding Transformer And Transmission Line Protection Of Collection Station Where Cluster Of Wind Farms Put In

With the development of large scale cluster wind farms,there are more and more situations in which three winding transformers are incorporated into the power grid.Then the adaptability of the three winding transformer protection device and the sending out line protection device in the double fed cluster wind farm is further analyzed in this paper.First of all,the fault characteristic of DFIG is analyzed theoretically when the three winding transformer or the sending out line fails,and the electromagnetic transient model of wind farm is built on PSCAD/EMTDC,then the simulation verification is carried out.It is found that the phase error is very large when Fourier algorithm is used to measure and calculate frequency phase,so that the fault current frequency of transformer or sending out line are different.Secondly,the adaptability of the longitudinal differential protection of three winding transformer and the distance protection of sending out line in the wind farm is discussed.The protection module are established on the PSCAD/EMTDC simulation software,and then the influence of DFIG fault characteristics on longitudinal differential protection and distance protection is simulated and analyzed.It is found that the action current and the braking current of differential protection fluctuate greatly,and the distance protection elements cannot accurately measure the measuring impedance from fault point to the protection installation,So that the differential protection device and the distance protection device can not be accurately act.Finally,Taking the fault characteristics of the DFIG wind turbine and the action characteristics of the differential protection in the wind farm as the base point,and considering the influence of the setting coefficient on the action characteristics of the transformer protection,we put forward reasonable corresponding strategy for the configuration of RCS-978 series protection devices in the cluster wind farm.