The utility model relates to a protective appliance for power facilities, in particular to a dismountable combined protective clapboard for a transformer substation. The dismountable combined protective clapboard for a transformer substation comprises a pair of vertical stanchions that are arranged in parallel; the lower end of the stanchions is connected with a bracket; the stanchions consist of multiple sections of telescopic rods that are sheathed with each other; telescopic joints are used for positioning among all telescopic rods; and an insulating clapboard is connected between the pair of telescopic rods at the uppermost end of the two stanchions. The dismountable combined protective clapboard has simple structure, and is convenient to manufacture and install. As the main material used for the clapboard is the epoxy resin which has light mass and high mechanical strength, the insulating protection function is improved, and the safety of human body and electric network is guaranteed. The isolation and protection requirements on the works at different heights can be met by adopting the telescopic stanchions.