Embodiments of the present disclosure provide a switch assembly for a detection unit of a switchgear or controlgear. The switch assembly includes a shaft rotatably arranged between opposite side walls of a compartment for accommodating an electrical component, the electrical component coupled to at least one connecting busbar of the switchgear; at least one conductive unit, each conductive unit being rotatable about the shaft between an open position and a close position; and at least one coupling mechanism arranged in the compartment and configured to electrically couple the conductive unit to the detection unit, wherein each coupling mechanism is electrically coupled to the respective connecting busbar when the conductive unit is in the close position, and is electrically decoupled from the respective connecting busbar when the conductive unit is in the open position and is grounded, and wherein each coupling mechanism includes a connecting unit for receiving a terminal of the detection unit positioned outside the compartment. In this way, maintenance or replacement of the detection unit will not affect the airtightness of the compartment. Furthermore, the connecting unit can also be used to receive the terminal of other kind of detection unit, such as terminals of test assemblies.