特高压直流分压器传变特性及其对电压突变量保护影响

Analysis of the transfer characteristic of DC voltage divider in UHVDC system and its effects on undervoltage sensing protection

直流分压器是特高压直流输电控制保护系统的数据源头,其传变特性对直流线路保护适应性提出了新的课题。针对这一问题,从直流分压器的传变特性分析着手,建立了直流分压器分压回路等值电路模型,推导了直流分压器的传递函数,分析了其阶跃响应动态性能。特别地,研究了二次分压板拓扑结构以及低通滤波器截止频率对传变特性的影响。利用PSCAD/EMTDC,构建了西南某特高压直流电磁暂态仿真模型,仿真研究了直流分压器传变特性对电压突变量保护的影响规律。研究表明,当二次分压板取消低压臂电容时,故障后分压器二次侧感受到的电压突变量较实际电压突变量更大,有利于提升电压突变量保护的灵敏性,提升保护抗过渡电阻的能力。研究结论可为特高压直流输电系统直流分压器选型提供指导。

DC voltage divider is the data source of the control and protection system in UHVDC.A new topic is presented due to DC transformers connected to DC system protection.To solve this problem,the equivalent circuit model and the transfer function are proposed to analyze the transfer function of DC voltage divider.Meanwhile,the dynamic characteristic of step response of such transformer is also obtained.Especially,the effects of the topology structure of the secondary bleeder circuit and the cut off frequency of low-pass filter on the transfer characteristic is also illustrated.Then a±800 kV/8000 MW UHVDC system case study is utilized to research the effect of the transfer characteristic of voltage divider on undervoltage sensing protection.Simulation results show that the fault component of voltage in secondary side of voltage divider may be larger than that in primary side,if the capacity in low voltage arm of secondary bleeder circuit is canceled.In this situation,the sensibility and the anti-resistant capacity of undervoltage sensing protection can be increased.The conclusion can provide guidance for lectotype of the voltage divider in UHVDC system.