Numerical simulation of self-excited oscillation switching current in HVDC MRTB

This paper presents a numerical study of the current self-excited oscillations during the opening of high voltage direct current (HVDC) metallic return transfer breaker (MRTB). The switching arc is simulated using the magneto-hydrodynamics (MHD) theory coupled with the electric circuit variation. The simulation is proved accurate in simulating the current oscillation and the commutation process in MRTB by the good agreement between the calculated results and the experimental results, which are obtained on a MRTB prototype designed to break about 5 kA of DC current. Both kinds of the results show that the current oscillation starts at about 16.5 ms and the total arc time is about 24 ms with a commutation capacitor bank of 72 μF and an inductor of 173 μH. With a further analyze on how circuit parameters influence arc current oscillations, this study helps to improve the current interruption capability of MRTB.