Relay Protection Research On HVDC Transmission Line

Inrecentyears,the rigiditydemandforelectricpowerisalso increasingmagnify.Traditional AC transmission cannot meet the domestic requirement of the development of electric power.Meanwhile,for the geographical distribution of energy and load in China is very uneven,ithelppickup DCtransmissiontechnology.In the DC system,due to the long line,in the engineering practice,the DC line fault accounted for 50% of the total fault ratio,to carry out the research of DC line protection has a very high research significance.With the increasing voltage level of DC transmission,relay protection issues are also increasingly appared.DC transmission line protection is not maturity at present,The form of protection is single and fixed,so it's necessaryto study it more deeply.We first buildamodel for Xiangjiaba(Fulong)-Shanghai(Fengxian)± 800 kVHVDC transmission system,In the model,the parameters of each link of the DC system are considered,it also considered the actual line parameters of the DC line rectifier and inverter side AC system.At the same time,we have simulated the commutation failureto verifythe accuracy of the model control system.An accurate model is the basis for further research.At present,the main protection of DC line is traveling wave protection and differential voltage protection,Based on the existing traveling wave protection algorithm and protection criterion of ABB company,we verified the effectiveness of traveling wave protection under various fault conditions,moreover we analysis and summary to experiment results and points out the problems existing in the travelling wave protection and the development direction.Distance protection has been widely applied in the high voltage AC system and immunetothemodeofoperation.But in HVDC systems,Transmission line's length is generally above 1300 km.Conventional distance protection is difficult to play a role.In this paper,a new distance protection algorithm based on equal variation theory is proposed.We use the build model to verify the algorithm.Discussed the performance of the algorithm performance under various fault types.It provides a new research direction and thinking for DC line protection.At last,we used PSCAD/EMTDCplatformto build simulation model of HVDC system,and the simulation analysis was made on the protection algorithm respectively,then proves the effectiveness of each method.