In high voltage direct current(HVDC)transmission systems

the status of direct current(DC)transfer switch will influence the conversion of monopole from ground return(GR)to metallic return(MR). By analyzing an abnormal conversion process in Gezhouba-Nanqiao HVDC transmission system

this paper draws a conclusion that too high an induced voltage that occurred in the transmission line did damage to relevant components in the oscillation circuit of DC transfer switch. This leads to the operation failure of transfer switch protection and conversion. In light of the test results

some improvement measures and operation suggestions for this fault operation case are put forward as reference for people in design

operation and maintenance of HVDC transmission systems.