高压直流输电系统开路试验原理分析与工程建议

开路试验是高压直流输电工程投运前必做的一项基本试验。该实验中触发角与直流电压的关系具有特殊性。从换流阀电路模型入手,详细分析了在不带线路工况下换流阀的导通情况,推导出理想情况下直流电压与触发角的关系,并给出了理想电压公式的适用条件。使用三沪I回直流输电工程一次模型,在EMTDC中进行了不带线路和带线路工况下的开路试验,并对试验结果进行了详细的分析。分析和实验结果表明:带线路工况下,直流电压在触发角小于60o后到达额定值是正常的。开路试验保护中设置电压判据是不合理的,可只采用电流原理判据作为试验是否成功的依据。

Analyses on the principle of open line test in HVDC and some suggestion for its practice

The open line test must be done before HVDC transmission project is put into operation. The relationship between firing angle and DC voltage at open line test is not same as normal operation. Based on the circuit model of the valve and circuit principle, a detailed analysis about the turning on/off of the valve without connecting the DC line is given. A relationship between firing angle and DC voltage is obtained. And the scope for applying this relationship is given. A simulation in EMTDC software is employed to verify the analyzing results. Analysis and experimental results show that: without DC line, DC voltage will reach its rated value when firing angle is less than 60 degrees; the protection based on the voltage criterion in open line test is not reasonable. Only the current criterion in protection is needed for detecting whether the open line test is successful or not.