Quantitative Evaluation of Fault coverage for Digitalized Systems in NPPs using Simulated Fault Injection Method

摘要

In this study, fault detection coverage for a digital system is evaluated using a simulated fault injection method. The target system is a Local Coincidence Logic (LCL) processor in a Digital Plant Protection System (DPPS). However, as it is difficult to simulate the actual LCL processor for evaluating fault detection coverage, the LCL processor has to be simplified. Some assumptions are needed to evaluate the fault detection coverage. Among them, one of the most important assumptions is that the fault detection coverage of components is independent to each other. In order to detect faults, a fault detection mechanism is developed. In the experiments, heartbeat signals are emitted at regular intervals after executing logic without a self-checking algorithm. When faults are injected into the simplified LCL system, fault occurrence can be detected by checking whether the heartbeat signals are emitted from the simplified LCL system or not. As a result of simulations, more than 44% of all faults could be detected without a self-checking algorithm. In a different test with a self-checking algorithm, the fault detection coverage of PROM was increased.