微机保护开入量回路的有关问题分析

通过对开入量回路构成的各个环节以及多起典型保护误动事例进行分析,表明微机保护开入量回路设计中大量使用的光耦方案,存在动作电压偏低、动作功率偏小等问题,从光耦器件的选择、光耦回路的设计、外部接点的引入到光耦电源的使用等各环节,均应采取一定的安全可靠措施。装置内部元器件及读取回路的设计上,需要特别注意动作电压、动作电流、电平配合等问题;应该采用中间继电器对现有的重要开入量进行重动;光耦开入电源与变电站直流系统应进行有效的隔离;尽量少采用长电缆直接跳闸方式;尽量减少微机保护的开入量;优化保护内部逻辑,提高开入量容错能力;要提高保护装置对开入量的监视与报警能力。

Problem analysis about binary input circuit of microprocessor-based protection

The binary input circuits and some typical misoperations of protections are analyzed,which show that,the overuse of optical coupler in binary input circuit causes lower driving voltage and smaller driving power.Certain countermeasures are suggested,such as optical coupler selection,optical coupler circuit design,contactor connection,DC power supply,and so on.Pay great attention to the driving voltage and power of reading circuit,as well as the level matching.The important binary inputs should be relayed.The power supply of optical coupler should be effectively separated from the substation DC system.The direct trip via long cable should be avoided and the binary inputs should be as less as possible.The internal protective logic should be optimized,the error tolerance capability of binary inputs enhanced and the monitoring and alarming functions for binary inputs improved.