励磁涌流引发的谐波过电压机理分析以及抑制措施研究

Research on mechanism of harmonic overvoltage due to exciting inrush current and its suppression method

对励磁涌流引发的谐波过电压风险进行机理性分析,揭示出引发过电压的根本原因是输电线路传播的驻波效应和谐振效应共同作用。分析了断路器动作离散度、剩磁大小、对选相合闸最佳合闸时间的影响,推导了计及剩磁条件下合闸电阻理论投入最小时间,并根据实际工程要求,提出了一种在剩磁方向可测的条件下,综合利用选相合闸和合闸电阻的协调优化控制策略,该方法可在不超过常规设备能力的前提下,有效抑制空充主变时励磁涌流产生的谐波过电压。在四川某电网上进行了电磁暂态仿真测试,结果表明该方法真实有效,在不同工况下都能适用,具有较强的工程实用性和鲁棒性。

In this paper,the mechanism of harmonic overvoltage resulting from exciting inrush current is analyzed,and it is found that its essential reason is the combined action of standing-wave effect and the resonance effect on the transmission line. Moreover,the limitations of existing suppression methods,such as phase selection switch and closing resistor,are also analyzed. The phase selection switch requires the breaker switching time to be less than 1ms,which could be very difficult to achieve due to the discreteness of the breaker and the transformer residual magnetism in reality. On the other hand,if transformer residual magnetism is considered,the switching of the closing resistor can＇t suppress the exciting currents of all phases because of its switching time. Therefore,under the condition that the direction of transformer residual magnetism is known,a coordinated suppression control strategy of over-voltage produced by exciting inrush current is proposed in this paper,which optimizes phase selection and closing resistor switching. Electromagnetic transient simulation was carried out on a certain regional power grid in Sichuan,and results indicate that the proposed suppression method is effective and has some robustness under different operating conditions.