The ABB SS822​ is a specialized Power Voting Unit manufactured by ABB, designed as a critical component in safety instrumented systems (SIS) and other high-availability industrial control applications. This intelligent module continuously monitors multiple redundant power supplies, executes a voting logic to determine system health, and provides a validated power output to ensure uninterrupted operation of critical safety controllers and I/O modules.

In a hydrocarbon processing facility, the emergency shutdown (ESD) system protecting a gas compressor train must have 100% power availability. The system uses triple-redundant 24V DC power supplies. The ABB SS822​ Power Voting Unit constantly monitors the voltage and health status of all three supplies. During a severe thunderstorm, a voltage spike damages one power supply, causing its output to drop. The ABB SS822​ immediately detects this fault through its continuous comparison logic. It isolates the faulty supply, continues to power the critical safety controllers from the two remaining healthy supplies, and triggers a maintenance alarm—all without a single power interruption to the ESD logic solvers. This seamless failover, managed by the ABB SS822, ensures the safety system remains fully operational to execute a controlled shutdown if process conditions demand it, directly addressing the paramount pain point of safety system availability.