Top-level view of a power plant. The Supervisory Control block provides the
signal to start the power plant and sets the target output levels. The Local
Control block implements a simple control law to achieve the target output
levels. It also detects failures to receive sensor data from the network.
Upon the first such failure, it notifies the Supervisory Control block with a
warning. Upon the second such failure, it locally changes the target output
level to shut down the power plant, and also notifies the Supervisory Control
block.
With the test data shown here, a warning occurs at time 8. The plant resumes
normal operation at time 20. At time 22, an emergency occurs, and the plant
shuts down.