Analysis of Multiple Valve Units Steep Front Impulse Voltage Test of HVDC Thyristor Valve

Thyristor valve is the key equipment of HVDC transmission system. Dielectric tests mainly verify the voltage withstand capacity of valve support, multiple valve units and between valve terminals. In multi terminal DC system, thyristor valves need to withstand different types of voltages. In the previous UHV thyristor valve tests, steep front impulse test is not carried out, Steep front impulse test specifies the virtual steepness and crest value of voltage waveform. This paper calculates the feasibility of the steep front impulse test according to the thyristor valve and simulation load structure, analyzes the factors affecting the waveform steepness, and implements the test for $\boldsymbol{\pm 800 \text{kV}}$ thyristor valve, the adjustment method of front time and voltage distribution ratio in simulation load method is given.