某核电厂反应堆保护系统以继电器板卡作为输出驱动部件.在工厂测试期间执行第3阶段定期试验，当安全触发柜旁通开关从旁通打至正常，继电器板卡发出持续约20ms的瞬态触发信号.分析瞬态触发信号对机组正常运行的影响，结合继电器板卡内部结构解析保护系统第3阶段定期试验原理，总结出继电器跳变为产生误触发信号的根本原因.在不变动继电器板卡原有结构的基础上，通过增加固态定时器解决该问题，可为后续反应堆保护系统的相似设计提供参考.

Relay board is taken as the output driving part of the reactor protection system in one nuclear power plant. The third periodic test of the reactor protection system is done during factory test, and the phenomenon is discovered that the relay board issues trigger signals last about 20ms when the bypass of the safety trigger cabinet switches from bypass position to normal position. The influence of the transient trigger signal on the normal operation of the nuclear power unit is analyzed. The third periodic test principle of protection system is analyzed combined with the internal structure of relay board,and the relay jumping as the reason of false triggering is concluded. The problem is solved by adding the solid state timer without changing the original structure of relay board. It provides a reference for the similar design of the following reactor protection system.