天生桥—广州直流工程控制保护系统改造后的过电压分析

基于改造后的天生桥—广州±500 kV高压直流输电工程,计算分析了在换流变Y/Y线圈阀侧单相接地、交流相间操作冲击、逆变侧失交流电源和逆变侧闭锁而旁通对未解锁4种典型故障工况下的系统过电压,确保在改造后的控制保护系统下,系统各点过电压及避雷器能耗限制在合理范围内,各电气设备能安全运行。分析结果表明:换流变Y/Y线圈阀侧单相接地故障将在中性母线上产生较高过电压,中性母线避雷器能耗较大;交流相间操作冲击会在阀两端产生较大过电压,阀避雷器动作;逆变侧失交流电源会在逆变站交流母线产生较高过电压,交流母线避雷器动作。逆变侧闭锁而旁通对未解锁会在逆变侧直流极线产生很高的过电压,直流极线避雷器能耗较大。上述4种故障工况下,各避雷器能耗均未超过设计通流容量,避雷器能安全稳定运行。

Analysis on Overvoltage in Renovated Control and Protection System for HVDC Power Transmission Project From Tianshengqiao to Guangzhou

System overvoltages in the renovated ±500 kV DC power transmission project from Tianshengqiao to Guangzhou under four typical fault conditions,i.e.,single-phase grounding occurred at upper-half rectifier bridge side of wye-wye connected winding of converter transformer,interphase switching surge from AC system,loss of AC power supply occurred at inverter side and inverter being blocked with unblocked bypass pairs,are analyzed and computed to ensure overvoltage at different positions in the grid as well as energy consumption of arresters can be restricted within rational ranges by renovated control and protection system,thus the secure operation of all power equipments can be implemented.Analysis results show that higher overvoltages will appear at neutral-bus due to single-phase grounding occurred at valve side of wye-wye connected winding of converter transformer,and the energy consumption of neutral-bus arrester will also be higher;higher overvoltage will appear at the terminals of rectifier valves due to interphase switching surge from AC system and it makes valve arrester operated;higher overvoltage will occur at AC bus of inverter station due to the loss of AC power supply at inverter side and it makes AC bus arrester operated;a rather high overvoltage will appear on DC polar line at inverter side due to inverter being blocked with unblocked bypass pairs and it makes a high energy consumption of arrester of DC polar line.The energy consumption of all arresters does not yet exceed the designed discharging capability under these four fault conditions,thus secure and stable operation of all arresters can be ensured.