基于变频投切电阻的直流系统绝缘检测方法

Insulation Detection Method of DC System Based on Frequency Conversion Switching Resistance

针对目前所使用的直流系统接地故障的低频注入法,在测量时会给直流系统带来影响,而且直流系统+存在的分布电容使得此方法遇到很多问题,提出了一种以改变频率两次投切电阻使直流转换为交流从而进行绝缘检测的方法。通过在母线投人一条支路,控制开关与已知频率投切,经并联电容将方波变为三角波。经过两次投切以后,根据频率,通过测量并联电容两端电压和支路电流,经推导后公式排除支路分布电容的影响,计算即可得到电阻值,变换后的小信号由直流电流产生,满足DL/T 724-2000《电力系统用蓄电池直流电源装置运行与维护技术规程》的规定。该方法提高了检测精度,不考虑直流系统中分布电容的影响因素,增加了绝缘检测设备的检测能力,通过仿真验证了方法的可行性。

At present,the frequency injection method of grounding fault in DC system will affect the DC system when measuring,and the distributed capacitance in DC system makes this method encounter many problems.According to this situation,a method of insulation detection is proposed by changing the frequency twice switching resistance to convert DC into AC.By putting a branch into the bus.the control switch is switched at a known frequency,and the square wave is changed into a triangular wave through a parallel capacitor.After twice switching,according to the frequency,by measuring the voltage at both ends of the shunt capacitor and the branch current,the influence of the branch distributed capacitance is eliminated by the derived formula,and the resistance value can be calculated.The transformed small signal is generated by DC current and meets the requirements of DL/T 724-2000 Technical spedficatiun for operation and maintenance of DC power supply device for storage battery in pozver system.This method improves the detection accuracy,does not consider the influence factors of distributed capacitance in DC system,and increases the detection ability of insulation detection equipment.The feasibility of the method is verified by simulation.