大型发电机中性点组合型接地方式的分析与探讨

为限制接地故障电流，同时方便应用定子接地保护，大型发电机上采用了一种折中的组合型接地方式：在接地变压器低压侧负载电阻两端并联一个电感。给出了组合型接地方式的等值电路；对组合型接地方式进行选型计算，原则是电阻电流等于补偿后的电容电流，并将故障电流限制在10~25 A范围内。将组合型接地方式和常规的高阻接地方式进行了对比，对比结果表明组合型接地方式的并联电感值越小，越能有效地限制接地故障电流，但是采用组合型接地方式后失谐度、阻尼率会减小，进而导致传递过电压、位移电压有所增大。希望分析及探讨有助于组合型接地方式的选型设计及推广应用。

Analysis and discussion on combination-type grounding scheme for large-sized generator

In order to limit the grounding fault current and facilitate the application of stator grounding fault protection, a compromise combination-type grounding scheme is adopted for large-sized generators, which installs an inductor in parallel with the load resistor at the low voltage side of neutral grounding transformer. The equivalent circuit of combination-type grounding scheme is given. The design calculation of combination-type grounding scheme is carried out, and the design principle is that the resistance current should be equal to the compensated capacitive current and the grounding fault current should be limited within the interval of 10~25A. The combination-type grounding scheme is compared with the conventional high-resistance grounding scheme, and the comparative results show that the smaller the shunt inductor value of the combination-type grounding scheme is, the more effectively the grounding fault currents can be limited, but the detuning degree and damping rate will be decreased after the combination-type grounding is adopted, which leads to the increase of transfer over-voltage and displacement voltage. It is hoped that the above analysis and discussion would be helpful to the design and promotion of the combination-type grounding scheme.