There is a risk of fire in thyristor valve in DC power transmission system. In this paper

the experimental method of thermogravimetric analysis is combined with differential scanning calorimeter（TGA/DSC）as well as hotair furnace to study onset temperature of thermal weight loss

exothermic critical temperature and ignition temperature of polymer materials in the elements of the thyristor under air environment. The ignition method to measure of polymer material of thyristor valve by TGA/DSC experiment in the air environment is proposed. Through the correlation analysis of the three parameters

the factors affecting the ignition temperature of the polymer material of the thyristor valve element are determined. The study results show that the ignition process of the thyristor valve is under the joint action of the pyrolysis process of the polymer materials and the exothermic process at high temperature. The temperature required for the ignition process is positively related to the temperature of the pyrolysis process and the lowest temperature at which the material can rely on its own exothermic reaction to heat up. A number of combustion-related parameters of different polymer materials contained in converter valve in air condition is compared and analyzed

which can provide a reference for the study of ignition characteristics of the converter valve and the assessment of converter valve fire risk.