Research On Fault Identification Of HVDC Transmission Line

In the external environment of HVDC transmission corridor in China,it is necessary to correctly identify the fault of DC transmission line,which is the precondition of correct operation of line protection.The use of fault traveling wave to identify the DC transmission line fault can be affected by the transition resistance and the line electromagnetic coupling factors may make the DC transmission line failure to correctly determine the fault occurred on the DC transmission line,resulting in line protection refused to move;Or,in the case of lightning disturbance,the fault can be identified that the fault occurs on the DC transmission line,resulting in maloperation of the line protection.By analyzing the characteristics of DC transmission line and outside fault,it is concluded that the fault spot current and fault identification measured at DC transmission line is equal,and the correlation is high,and the fault occurs in DC transmission line because of the physical boundary of smoothing reactor and DC filter When the fault voltage waveform and normal operation voltage waveform of non-fault shielding failure,lightning strike fault and common ground fault are compared to normal operation voltage waveform,the voltage traveling wave only recovers to normal operation value after a slight disturbance,and the voltage drops below normal operation value.therefore,the voltage correlation criterion can be distinguished,and the method of using fault traveling wave characteristic quantity to identify the fault in the region is improved.The simulation results show that the method is reliable and the resistance to transition resistance can reach 300 ohm.