Research on Strategy of Setting Default Values for Safety-Level DCS in Nuclear Power Plants
Aiming at the problem that the arbitrary spreading of quality bits of invalid signals in digital instrumentation and control systems puts the system in an uncertain state,the fault diagnosis mechanism of the NASPIC platform and the identification of signal quality bits are investigated in the light of the operating conditions and signal characteristics of nuclear power plants.Considering the fail-safe criterion,the default value setting principle is systematically proposed.Analyzing from two dimensions of signal execution function and signal boundary,the range of default value setting is confirmed,and the default value setting strategy for signals executing protection function,alarm function,maintenance and test function is given in detail.At the same time,a new method of default value verification using full-range simulator and virtual digital control system(DCS)is proposed to address the problem that the traditional default value verification method is unable to carry out default value verification in a comprehensive and effective way.The method can be utilized to effectively and systematically verify the default value settings in DCS.The proposed default value setting strategy and validation method can provide comprehensive guidance for the analysis and setting of default values in the safety-level DCS of subsequent nuclear power plants.
Nuclear power plantsProtection systemsSafety-level digital control system(DCS)Fault diagnosisQuality bitDefault value