基于改进变频二次注入法的直流系统绝缘检测技术

针对现阶段直流系统接地故障检测所使用的频率注入法会给直流系统带来较大纹波和受到分布电容影响较大的问题,本文提出了在正负直流母线间串联交流电源并在母线增加短路电容通路的方法以提高检测精度。即根据两次变频注入交流信号得到故障支路的漏电流建立两个二元方程以在规避分布电容影响的前提下精确求得接地电阻。该方法向母线投入一个大电容支路,既能有效规避母线分布电容给测量带来的误差,又满足国家电网的规定,向系统注入的小信号在纹波规定范围内,还从计算上规避了支路分布电容的影响。该方法有效减小了由于传感器测量精度和分布电容对直流系统绝缘检测带来的误差,降低了绝缘检测设备漏报误报概率,提高了检测精度并使用实验仿真验证了方法的可行性。

Insulation detection technology of DC system based on improved frequency conversion two injection method

In view of the problem that the frequency injection method used in current DC system grounding fault detection will bring large ripples to the DC system and is greatly influenced by the distributed capacitance, this paper proposes a method to increase the detection precision by adding the AC power to the positive and negative DC buses and adding the short circuit capacitance path on the bus.That is the leakage current of the fault branch is obtained according to the two frequency conversion injection of AC signals,two two element equations are established to accurately calculate the earth resistance under the premise of avoiding the influence of distributed capacitance.This method can input a large capacitance branch in the bus bar, which can effectively avoid the error caused by the busbar distributed capacitance and meet the requirements of the State Grid.,and the small signal injected into the system is within the specified range of ripple,the influence of branch distribution capacitance is also avoided.The method effectively reduces the error caused by the sensor measurement precision and the distributed capacitance on the DC system insulation detection, reduces the false alarm probability of the insulation detection equipment, improves the detection precision and uses the experimental simulation to verify the feasibility of the method.