Study On The Transmission Line Protection Of The Uhv Grid

With the 1000kV demonstration project completed, the power system will gradually form national interconnected UHV grid. It is necessary to study the effect of the UHV grid electromagnetic transient on the extra-high-voltage line protection, it is also necessary to study the new protection of the UHV transmission line. To study the UHV grid electromagnetic transient, on the basis of the PSASP and PSCAD/EMTDC, the UHV grid simulations model and RTDS model was built. The method of the short circuit current calculation prove UHV grid simulations model is reliable.By two kinds of UHV transmission line, detailed analysis of the study of the effect of the UHV grid electromagnetic transient on the extra-high-voltage line is presented. The result show that the harmonic and decaying DC component are very big, and the decaying time is also very long, especially the third harmonic. In general, the nearer the measurement points from the UHV line, the greater the effect of the UHV line.On the basis of the study of the UHV grid electromagnetic transient, study of the UHV line protection of the directional pilot protection,distance pilot protection,differential pilot protection is presented. By the study of the 189 fault, when nanyang-jindongnan of the 1000kV UHV transmission line occur three-phase short circuit fault, the simulation result show that the fault component differential protection of the douli-fancheng and douli-xiaogan will appear misoperation. When the low pass filter is increased, the misoperation will disappear.On the basis of the original study of the energy balance protection, Dynamic simulation experiments of the 1000KV transmission line was used to study the protective effect of the energy balance protection. A method of transmission line resistance using tuning value and transmission line Inductance and capacitance using the corrected average value of the three module is presented in this paper. The actual line parameters are obtained by the method. Dynamic simulation experiments of the 1000KV transmission line show that the two energy curves of the external fault are consistent with each other. Under any complex fault conditions of power system, energy balance protection based on three spatial module has excellent performance, it can switch off the faulty phase when single line-to- ground fault occurred.In this paper, the study are summarized, and the direction for further research is pointed out finally.