一种新型微机直流操作回路接地检测和短路保护装置的研制

A NEW DEVICE DETECTING GROUND FAULT AND SHORT CIRCUIT PROTECTION FOR DC CONTROL CIRCUIT

直流操作回路在运行过程中由于接地点的难以准确定位和缺乏有效的直流短路保护等原因,导致有时发生电力主设备损坏的重大事故。因此,对直流操作回路接地点的准确定位和短路保护装置的研制具有重大现实意义。作者首次将交流系统三段式电流保护的概念及逻辑判据应用于直流操作回路,构成了三段式直流短路保护,同时提出了以霍尔电桥检测直流操作回路接地故障的新方法,并根据其原理研制了相应的装置。数值仿真和模拟试验表明本文方法能克服直流操作回路分布电容电流的影响,准确检测出直流操作回路接地故障,并能准确快速地识别并切除直流操作回路的短路故障。

The difficulty of accurately locating the grounding position in the DC control circuit and the absence of effective short circuit protection device for the DC control circuit may cause the serious accident which leads to the damage of main power equipment, so it is of important significance to accurately locate the grounding point in the DC control circuit and to develop its short circuit protection device. In this paper the concept of three-step current protection and its logical criteria for AC system are firstly applied to the DC control circuit and a three-step current protection for DC control circuit is suggested. At the same time, a new method to detect the grounding fault occurred in DC control circuit by Hall electric bridge is put forward and according to this principle a corresponding device is developed. The results of simulations show that the presented method can overcome the affect of distributed capacitive current in the DC control circuit and the grounding fault in DC control circuit can be accurately detected. Besides, the short circuit fault in DC control circuit can be correctly and rapidly identified and switched-off.