Main causes of long-standing alarms and their removal by dynamic state-based alarm systems

•The main causes of long-standing alarms being nuisance are identified.•Industrial examples are provided as supportive evidences of the identified main causes.•A dynamic state-based alarm system is proposed to remove long-standing alarms.•Two rules are formulated to select state variables.•Industrial case studies illustrate the effectiveness of the dynamic state-based alarm system.

Long-standing alarms are those in the alarm state continuously for a long period of time. Some long-standing alarms belong to nuisance alarms, playing a detrimental role to the performance of industrial alarm systems, and hence they should be removed. The paper analyzes the main causes leading to long-standing alarms as nuisance ones; industrial examples from a large-scale thermal power plant are provided as supportive evidences of the main causes. A dynamic state-based alarm system is designed to remove long-standing alarms caused by the inconsistency between the alarm design and discrete-valued operating states. The design is based on two rules formulated to select state variables and a novel alarm generation mechanism to generate state-based alarm variables. Industrial case studies illustrate the effectiveness of the dynamic state-based alarm system in significantly reducing the severity of long-standing alarms.