Emergency shutdown system [for industrial power systems]

The authors describe a recent application using redundant programmable logic controllers that provides online diagnostic checking of input/output devices, verifies operation response of shutdown logic, reduces the probability of a fail-dangerous condition, and reduces false trips to rare events. They describe the steps taken in developing the system and examine the various self-checking features (digital input and output checking and analog input checking). They also describe the test logic operation. The authors believe that their approach will result in a high level of confidence in industrial power system operability and in lower costs