DC controllable arrester based on thyristor is the key equipment of hybrid cascade UHVDC transmission system. The thyristor control unit (TCU)

as the drive and control device of its key switching device thyristor

plays very important role for reliable operation of DC controllable arrester thyristor. The thyristor of DC controllable arrester operates in high voltage and DC condition. The design of its TCU is different from that operating commonly in the condition of AC voltage. In this paper

the operating principle of the DC controllable arrester is introduced firstly. Then the operating principle of TCU of the controllable arrester is analyzed. The TCU is divided into five circuit function modules and design schemes of the each circuit function modules are given. Triggering and control of thyristor operating in DC voltage is realized. The prototype is designed in accordance with the design requirements of TCU for DC controllable arrester of some actual projects and the rationality of the design is verified by test.