基于现场总线的分布式直流系统接地在线监测装置设计

采用了一种常态下利用双不对称电桥实时监测直流系统绝缘的方法,解决了正负母线绝缘均按比例下降时失效的问题。并在低频信号注入法的基础上提出了双变频测量法,测量各支路的接地电阻值,从而判断出故障支路,解决了低频信号注入法容易受到直流系统支路中存在的对地分布电容的影响问题。详细介绍了基于现场总线的分布式接地监测系统的设计与实现方法,每个前置采集单元就近检测一定数量的支路接地电阻,并通过CAN总线互连,将检测数据上传到集中处理单元。实验和现场运行表明该系统布线少、配置灵活、测量精度高、支路接地故障定位的准确率高及抗干扰能力强。

Distributed on-line grounding monitoring system for DC system based on field bus

A new method is adopted to real-timely monitor DC system insulation,which applies double asymmetrical bridges to keep it effective when positive and negative pole insulations drop in same proportion.Additionally,double-frequency measurement based on low-frequency signal injection is put forward for branch grounding resistance measurement in faulty branch selection to avoid the influence of the distributed grounding capacitance of DC system on low-frequency signal injection.The design and realization of field bus-based distributed grounding monitoring system are introduced.The front-end acquisition unit measures the nearby branch resistances and sends the data to the centralized processing unit via CAN bus.Experiments and actual field operations show its less wiring,flexible configuration,high measurement precision,high veracity of faulty branch locating,and strong anti-interference capability.