SCADA for POWER GENERATION

CASE STUDIES

PROBLEM DESCRIPTION AND SYSTEM REQUIREMENTS:

A power producer in the Midwest United States operates a combined cycle plant consisting of two turbines, two waste heat boilers with afterburner controls, and a steam turbine. A fault tolerant control system was needed to limit the number of outages due to controls failures. To serve as an operator interface and update the systems' real-time database, the SCADA system had to provide continuous operation. In addition, the client wanted a system that plant personnel could maintain, modify, and enhance without having to rely solely on the vendor.

There are three standalone PC-based local control stations: One for each gas turbine/boiler combination and one for the steam turbine/coordinated controls. The fourth station, the main system running RealFlex, gathers the information from the local machines. The connection is made via LanFlex over an ARCNET network. The main node is duplicated by fault tolerant controllers. For continuous operation, each local station processes its own data and passes it onto the RealFlex main node. RealFlex also polls the controllers over a second communication link.
During normal operation, RealFlex constantly checks the integrity of the link and of each controller. If the backup link fails, the system prints an alarm. If the information from the local node is disrupted, the main node's backup link for that controller gathers the information directly. RealFlex monitors the boilers and turbines, if a process upset occurs, alarms alert operators to potential problems. Under defined shutdown conditions, the controllers trip the process and RealFlex updates the operator and maintenance personnel on what has occurred.

RealFlex and accompanying controllers provide a fault tolerant system to prevent downtime. Processes can be performed continuously without any costly interruptions.