Research on the Risk of Hot-Swapping in Safety-Class DCS Based on Sneak Circuit Analysis

In nuclear safety-grade Distributed Control System, to enhance the rapid maintenance and replacement capabilities of the DCS system, reduce Mean Time To Repair (MTTR), and improve maintainability, it is necessary to insert or remove modules without powering down the DCS system, ensuring that the normal operation of other modules in the system is not affected during the process. Due to the uncontrollability of human error, there is a certain degree of randomness in the insertion and removal of hot-swapping modules, leading to various combinations of signal contact sequences. Furthermore, in complex application scenarios involving intricate module combinations and chassis structures, unexpected states that deviate from the design may arise, potentially impacting the normal functionality and performance of the system. Based on the electrical characteristics of the hot-swap circuit network in the DCS system, this paper integrates graph theory, path searching, and analysis to determine the various transient and steady-state circuit conditions of hot-swapping under different initial contact states. By examining the combined states of practical engineering applications and conducting path searches for potential pathways in the minimal application units of hotswapping, we identify weaknesses in the design of hot-swap circuits. Additionally, we analyze real-world cases of potential risks and propose improvement recommendations. This work provides a latent pathway analysis method for the subsequent application of hot-swapping in DCS systems, thereby enhancing the safety and operational reliability of safety-grade systems.