A modular electrical switch device including: a cut-off unit including unitary cut-off units; an actuating unit of the unitary cut-off units including an electromagnetic actuator including a fixed cylinder head and a movable reinforcement; a mechanism allowing the actuating unit to be fixed to the cut-off unit; a quick attachment mechanism allowing removable fixing of the actuating unit on the cut-off unit, and including at least one coupling hook configured to fix and hold the cut-off unit to the actuating unit, and to engage with an actuating device of the unitary cut-off unit to transmit movement of the actuator.

A DC relay is disclosed. According to an aspect of the present disclosure, the DC relay includes a main contact part that is electrically connected to an external power source or an external load; a sub contact part that is electrically connected to an external control power source and receives a control signal or current for controlling an operation of the main contact part; and an arc chamber having a space in which the main contact part and the sub contact part are accommodated, wherein the main contact part comprises a plurality of fixed contactors disposed to be spaced apart from each other along one direction inside the arc chamber, and the sub contact part comprises a plurality of sub connectors disposed to be spaced apart from the plurality of fixed contactors.