Analysis and Simulation on Current Commutation of the DC Transfer Switches in UHVDC Transmission Systems

Taking the Jinping-Sunan UHVDC project as the application background,the four kinds of transfer switches are analyzed and simulated.The functions of metallic return transfer breaker(MRTB) and ground return transfer switch(GRTS) during the commutation between the metallic return mode and the ground return mode as well as the functions of neutral bus switches(NBS) and neutral bus ground switches(NBGS) during particular faults are illustrated.Taking the MRTB for example,the commutation process and the influence of the counter-voltage level on this process are analyzed.The parameters for the four kinds of transfer switch in UHVDC system are studied and calculated with simulation in PSCAD/EMTDC.The parameters of the transfer switches such as currents to be commutated,recovery-voltage levels and the energies to be absorbed are given;and these parameters could be the criteria for designing.