直流起励过程中绝缘监测系统对转子接地保护的影响及对策

Influences of insulation monitoring system on rotor grounding protection during DC excitation process and countermeasures

发电机直流起励过程中转子接地保护可能报警或跳闸,因此通过现场案例分析动作原因。通过分析直流起励过程中绝缘监测系统和转子接地保护构成的回路,推导出转子接地电阻计算公式,计算公式表明转子接地电阻阻值与直流绝缘监测系统的平衡电阻和接地电阻有关。当转子接地保护电阻值整定偏灵敏时,如果直流绝缘监测回路的接地电阻值不足够大,就可能导致转子接地保护报警或跳闸。基于理论分析提出了相应的解决方案。

The improper alarm or trip of rotor grounding protection during the DC excitation is analyzed based on a field case. The circuit composed of the DC insulation monitoring system and the rotor grounding protection is analyzed,and the calculation formula of rotor grounding resistance is deduced,which shows that the rotor grounding resistance is related to the grounding resistance and balance resistance of DC insulation monitoring system. When the resistor settings of rotor grounding protection are biased towards sensitivity,if the grounding resistance of DC insulation monitoring circuit is not large enough,the rotor grounding protection may improperly alarm or trip. Corresponding solutions are given based on the theoretical analysis.