Abstract: To address dispersed fault scenarios, unclear emergency-shutdown boundaries, and experience-dependent early response for major generation, transformation, and transmission equipment in large hydropower stations, this study proposes a four-stage engineering method comprising system decomposition, scenario database construction, three-dimensional grading, and closed-loop response. Equipment abnormalities are organized into standard scenario entries containing signals, causes, phenomena, consequences, and response boundaries. A three-level criterion is then established according to consequence severity, escalation urgency, and field controllability. The method converts scattered rules and operating experience into searchable, reviewable, and trainable response knowledge, improving the accuracy, timeliness, and standardization of early emergency handling.