基于流敏电阻非有效接地系统PT谐振过电压抑制

PT Resonance Over-Voltage Suppression Technology for Non-Effective Grounding System Based on Current Dependent Resistor

非有效接地系统中,电磁式电压互感器(PT)故障频发,对电力系统运行安全造成极大威胁,已有的铁磁谐振过电压抑制措施在技术性或经济性方面均存在一定的缺点,且针对接入电缆后电容电流过大的风电场等系统也没有针对性的消谐措施。通过对某地区10 kV与35 kV配电系统的铁磁谐振现象进行分析,提出应用于非有效接地系统的基于流敏电阻的电磁式电压互感器一次侧消谐方法:通过试验,得到流敏电阻值随吸收能量达到一定阈值后迅速增大;利用电磁暂态仿真计算软件(ATP-EMTP)进行仿真,将该流敏电阻应用于10 kV与35 kV非有效接地系统中,得到PT一次侧中性点经流敏电阻接地和PT高压侧串接流敏电阻均可以有效抑制铁磁谐振;并对比流敏电阻在不同电压等级下消谐过程中的电阻特性变化,获得其发挥最优电阻特性的条件,对流敏电阻抑制铁磁谐振的工程应用提供参考。

In non-effectively grounded systems,electromagnetic potential transformer(PT)faults occur frequently,which poses a great threat to the safety of power system operation,the existing ferromagnetic resonance overvoltage suppression measures have certain shortcomings in terms of technology and economy,and there is no targeted harmonic elimination measures for wind farms and other systems with excessive capacitive current after cable connection.Therefore,the author analyzes the ferromagnetic resonance phenomenon of a 10 kV system and a 35 kV system in a certain area,and proposes a harmonic elimination method for the primary side of an electromagnetic voltage transformer based on a current dependent resistor.Through experiments,it is obtained that the value of the current dependent resistance reaches a certain threshold with the absorbed energy,and then it increases rapidly.Using electromagnetic transient simulation calculation software(ATP-EMTP)for simulation,the varistor is applied to 10 kV and 35 kV non-effective grounding systems,and it is found that it can be installed at the high voltage side of the PT and the neutral point of the primary side to suppressing ferromagnetic resonance effectively.the resistance characteristics changes of the varistor in the process of harmonic elimination at different voltage levels are compared,and the conditions for its optimal resistance characteristics are obtained.