Study on MVU Tests Method of ±1100 kV Thyristor Valves for HVDC Power Transmission

The multiple valve units (MVU) consist of four valve units connected in series. MVU tests based on quadruple valve have some problems, such as large size test circuit, high test cost and so on. In order to solve these problems, MVU tests based on simulation load (SL) are put forward. A valve unit should be shorted and the valve unit remaining must be real thyristor valve unit when the MVU tests are conducted. So the simulation load is expected to take place of the two valve units equivalently. And the waveform on the valve unit remaining is the difference of waveforms on MVU and SL. But the time parameters of waveforms on MVU and SL are different when the MVU tests based on traditional SL is conducted, so the valve unit remaining may withstand very high voltage and even has the risk of being damaged. New SL should be designed for MVU tests and solve these problems. The SL of MVU d.c. withstand voltage test only consists of resistance, the SL of MVU switching impulse (SI) test only consists of capacitance, and when MVU lightning impulse (LI) voltage test is conducted, the SL consists of capacitance and the valve unit remaining should be connected in parallel with a suitable capacitance. Through the actual MVU tests of ±1100kV thyristor valves in our UHV laboratory, the time parameters of waveforms on MVU and SL are almost same when these simulation loads and test methods are used for MVU tests, and the valve unit remaining can avoid being damaged.