Zhangzhou Nuclear Power Plant uses the "Hualong No.1" -the third generation nuclear power reactor type. Its digital reactor protection system (referred to as Security Level DCS) uses the NASPIC independently designed and developed by CNNC GROUP for the first time to realize the protection functions such as shutdown and special action. The NASPIC innovatively designs "bypass function", including "channel bypass" and "parameter bypass", which can bypass the whole protection channel or part of the protection parameters during regular test or fault handling, reduce the possible rejection or misoperation of the protection action caused by the triggering of instrument quality state(Signal quality state) and channel fault. However, the use of "bypass function" will degrade the protection logic, and in CNNP's nuclear power plants, there is no precedent, and certain risks exist. This paper aims to analyzes the risk and application feasibility of "bypass function" based on the design principle of "bypass" function of safety level DCS of Zhangzhou Nuclear Power Plant, to provide examples for future unit operation.
