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Hybrid circuit breakers are a class of protection devices to facilitate fault current limitation and fast interruption in AC and DC power systems. They are one of the key enabling technologies of multi-terminal DC transmission and distribution systems. As the power rating of DC power systems increases, mechanical switches in the normal conduction path are chosen to provide low on-state loss in a hybrid circuit breaker topology. These mechanical switches require fast actuation to achieve sub- millisecond switching capability, for which only a few actuation mechanisms have been reported to be suitable. Besides electromagnetic repulsion methods like the Thomson coil, piezoelectric actuators also appear to be a good candidate. This paper provides a survey on potential mechanical switches for hybrid circuit breakers considering different actuation mechanisms. Performances of mechanical switches reported in the literature have been summarized and compared, such as response time, displacement, and required actuation energy.