High Voltage Direct Current Transmission Lines Protection And Its Identification Of Lightning

Existing high voltage direct current transmission line traveling-wave protection has dead zone,and longitudinal differential protection serves as backup protection because it cannot avoid distributed capacitive current.The similarity between aerial mode voltage traveling wave at rectifier side and inverter side is derived in this paper: there is a great discrepancy between the waveforms at two side when an internal fault occurs,there is a high similarity when an external fault occurs.Therefore,a high-speed primary protection scheme for HVDC transmission line based on Hausdorff distance comparison is proposed,which introduces scanning method to align the waveforms at two sides,then their correlation is analyzed,and Hausdorff distance is used as the protection criteria,this scheme can eliminate the influence of distributed capacitive current.Finally,a model is constructed on PSCAD/EMTDC to verify the proposed protection scheme,and the simulation results shows that this protection is of high reliability.Besides,it has a low requirement for time precision,an outstanding ability to resist the transmission resistance grounding,noise and abnormal data.When a fault occurs at the dead zone of the lines,the proposed protection can lock the travelling waveform protection.As for the identification of lighting,this paper focuses on the model of lighting current,the model of tower and the model of arrester and their construction in software PSCAD.By analyzing the transmission formula of backward traveling-wave line-mode voltage in the scenario of lightning stroke failures and lighting disturbances,the variation character of the measurements and the features of shielding and back flashover,the theory is then proved by using simulation on PSCAD.By constructing transient energy and accumulation energy,and using myriad of simulation results of various scenarios as the sample to train the multi-class classification support vector machine,and the results show that this support vector machine can effectively distinguish lightning stroke failures,lighting disturbances and line-to-ground faults.