The paper focuses on the role of disconnectors for load transfer duties in the operation of MTDC meshed grids. As there are no topology existing today and no standard, some switching duties are presented for which disconnectors could act instead of using circuit breaker. Based on an empirical model relying on tests performed in air, severity of the different switching duties are presented and first conclusions are proposed.

In view of the increasing global market for high voltage (HV) vacuum circuit breakers in the voltage rating ≥ 72.5 kV, it is necessary to focus our attention on developing the vacuum interrupters (VIs) for these ratings. VCBs have already penetrated the 72.5 kV market and trials are progressing with introducing up to 145 kV VIs into the power networks. Prototype of the 252 kV VI has already been demonstrated.