基于变频信号法的一种对地电容电流检测系统

A capacitive current detecting system based on variable frequency method

现有的基于变频信号法的对地电容电流检测系统多采用PWM逆变的方式作为扫频信号源,在应用中受到较多制约。对对地电容电流检测系统进行重新设计,检测系统的测量单元采用双单片机模式,信号源部分使用单片机控制DAC芯片作为数控信号源,经模拟实验验证在该应用中其性能优于传统的PWM逆变方式扫频信号源。相位测量部分由C8051F20片上系统兼顾相位检测与通信功能,上位机软件基于C/S构架搭建。该检测系统测量一次电容电流的时间不超过10 s,经现场实验验证了样机的测量误差在±2%以内,可直接应用于中压配电网的预调式消弧线圈,进一步设计后可应用于随调试消弧线圈。

The existing line-to-earth capacitive current detecting system based on variable frequency method uses PWM inverter as variable frequency source, which has many constraints in practical use. This paper redesigns the detecting system. Each measure unit is constructed with double single-chip computer model and uses single-chip to control the DAC chip as the variable frequency source. The model experiment proves that the DAC type variable frequency source has better performance than the source based on PWM inverter. The system-on-chip of C8051F20 is in charge of the phase detection and communication function. The build of upper computer software is based on the C/S architecture. This detection system can detect the capacitive current within 10 seconds and the field experiment proves that the measuring error is under ±2%. This system can be directly applied to the preset arc suppression coil in medium voltage distribution network;it can also be applied to the post-set arc suppression coil after further designed.