Success Story: Electrical Energy
Hoosier Energy (Usa)
1000 MW Station upgrades to PLC-based auxiliary Control System
I. CUSTOMER ENVIRONMENT / PROJECT CONTEXT
Hoosier Energy, Bloomington, IN, serves 18 rural electric membership cooperatives distributing power in southern Indiana.
The former auxiliary controls at the two-unit, coal-fired, 1000 MW Merom Generating Station represented a mixed bag of technologies: relay-based, proprietary black box and proprietary chip to gate-based controllers and statement language programming. A few had early PLCs. No effort was made to coordinate the various systems when the station was built. Many of the systems were difficult to troubleshoot and poorly supported. Spares were expensive.
Customer objective and constraints:
Although the original controls never impaired station availability, they threatened to do so from time to time. This concern drove Hoosier Energy to replace the most troublesome systems first.
II. SOLUTION IMPLEMENTATION
Implementation methodology (main phases):
Believed unique for a station of this size, the planning, engineering, installation, and start-up of the replacement controls and networks were almost entirely performed by station personnel, supported by Schneider Electric.
The upgrade of the late-1970's era controls occurred over a seven-year period, from 1991 to 1998.
Solution overview (services, products, systems, architectures...):
The controls conversion project totals 29 Modicon® PLCs and 23 PC-based operator stations, all residing on five Modicon Modbus Plus networks bridged together. The only original controls still in place are those for the boilers, turbines, burner management, and scrubber analog control and operator console.
The upgrade work was accomplished by Corie Biggs and Tony Cornelius, production engineers, with assistance from the Electrical Maintenance and the Controls and Instrumentation groups. During outages, additional electricians and technicians were assigned to projects as needed. Cornelius and Biggs developed the control and communication systems, wrote the programs, and prepared the operator screens.
Although different Modicon PLC models have been installed since the upgrade project began in 1991, all are fully backward and forward compatible. Every PLC resides on a network and can be programmed and maintained using Modicon Modsoft software and Modicon 984 conventions. The five 1.0 Mbps Modbus Plus networks already in service are bridged together, allowing them to operate as one large network. Fibre optic backbones eliminate lightning damage and electromagnetic interference, and permit communication lines to be routed in power cable trays.
When upgrading each system, long-standing problems such as a poor control strategy or lack of operator information were solved by adding more points. For example, the single status light that covered all four clamps on the rotary car dumper has been replaced with a separate status indication for each clamp. Other additions have included automatic start-up, improved interlocking, remote
monitoring, more sensors, etc.
III. RESULTS / ACHIEVEMENT
The in-house conversion resulted in numerous advantages:
Customer testimonies (Verbatim):