INVESTIGATION ON OPEN LINE TEST PRINCIPLE OF HVDC

The influences of the variation of firing angle of the converter on open line voltage, energization current and valve voltage are researched under the condition of open line test (OLT) with DC line, and the obtained conclusions are as follows: when the firing angle of the converter is reduced to less than 60°, the DC voltage can be still risen to its rated value; the energization current under the OLT will be constant while the firing angle of the converter is less than 60° and this current mainly depends on the structural parameters of DC transmission line and the intensity of the corona discharge; the lower the firing angle of the converter is, the smaller the voltage aberrance of valve arm will be. The personnel who engaged in the commissioning test of Three Gorges to Guangzhou HVDC projet approve these conclusions. In the OLT carried out at a certain converter station, when the firing angle of the converter is reduced to 35.7°, the open line voltage can be risen to rated value 500kV.