Besides electrical and mechanical design for thyristor valve

one of the key equipments for high voltage DC power transmission project

choose of electrical components is also an important work.With the development of high power electronic devices

techniques and stability of the electrical components have been substantially improved and thyristors of 6 inches have been commonly used in thyristor valves for ultra high voltage DC power transmission projects.Before put into operation

dielectric type test on thyrisotr valve should be done to verify dielectric performance of thyristor valve.This paper is a study on non-periodic firing test which is included in dielectric type test on ±1 100 kV UHVDC thyrisotr valve.Non-periodic firing test is the most severe test on thyristor valve

whose purpose is to verify if valve can withstand impulse current on switching impulse voltage

and to test if VCM can properly protect thyristors during turn-on and turn-off.The writer studies on the non-periodic firing test for ±1 100 kV thyristor valve with PSCAD stimulation software

which shows that single valve can stand impulse current of about 6 045 A when required switching impulse voltage of 574.4 kV is applied on single valve.