Experimental Study on the Effect of Surface Contamination on the Function of Thyristor Voltage Monitoring Board

This paper reproduces failure of thyristor voltage monitoring (TVM) board by artificial experiments and the effects of contamination and environmental conditions on TVM function are studied. The results show that the increase in relative humidity can lead to the deviation of check-back signal while the effect of temperature change is insignificant. The increase in both equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) can reduce the humidity threshold of TVM. According to the test results, measures such as decreasing the environmental relative humidity before the converter valve is back in operation, or cleaning device regularly are proposed to avoid TVM failure.