Ultra-fast disconnector (UFD) is a key component of hybrid DC circuit breakers and it is also studied as the main switch in some DC grid topologies. A UFD model suitable for DC grid studies and considering both normal operation and failure mode is presented. The dynamic motion of contacts is analysed in detail and it is concluded that Thomson coil inductances including parasitic parameters play an important role and it is recommended to use finite element modelling. The arcing mode of UFD is repressed using a variable resistance in series with an ideal switch. The variable resistance is calculated analytically based on the instantaneous position of contacts and the circuit conditions. Two different arc models are recommended: for the air-insulated UFD and SF₆ UFD, and in each case, two operating regimes should be considered: high and low currents. The UFD model is verified for both normal operation and failure mode using measurements on a 5 kV laboratory UFD and the results show very good matching. The 320 kV SF6 UFD model is evaluated using limited reported results from manufacturers.

超快速断路器（UFD）是混合直流断路器的关键组件，在某些直流电网拓扑中，它也被作为主要开关进行了研究。提出了适用于直流电网研究并考虑正常运行和故障模式的UFD模型。详细分析了触点的动态运动，得出的结论是，包含寄生参数的汤姆森线圈电感起着重要作用，建议使用有限元建模。通过使用与理想开关串联的可变电阻来抑制UFD的电弧模式。可变电阻根据触点的瞬时位置和电路条件进行解析计算。建议使用两种不同的电弧模型：用于空气绝缘的UFD和SF ₆UFD，在每种情况下，均应考虑两种运行方式：高电流和低电流。通过在5 kV实验室UFD上进行的测量，可以验证UFD模型在正常运行和故障模式下的运行情况，结果显示出很好的匹配性。使用制造商的有限报告结果评估了320 kV SF6 UFD模型。