Reliability evaluation of the converter valve is very important in HVDC transmission system

especially the reliability evaluation of the thyristor valve in the special environment of EMP（electromagnetic pulse）. However

the existing reliability evaluation method is not applicable to the evaluation and calculation of the reliability at special environment and the complex operating conditions of the electromagnetic pulse.Therefore

the life evaluation of thyristor valve under special environment is worth studying deeply. In this paper

the main failure evolution mechanism of the press-pack thyristor used in the HVDC transmission system under the electromagnetic pulse environment is analyzed in detail

and then a life prediction method considering the thermal impedance model of the converter valve cooling system and the thyristor failure mechanism is proposed The thermal stress calculation model of thyristor under electromagnetic pulse is established

and the life model of thyristor is obtained. Finally

the quantitative analysis process and results are presented and the main destructive effect of a special electromagnetic pulse environment on the converter valve is explained.