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Retrofitted state-of-the-art control systems improve plant performance

Issue 3 and Volume 105.

By Joyce L. Dasch, Westinghouse Process Control, Inc.

Across the U.S., electric utilities are looking for solutions to improve the performance of their generating units. Automation technology and advanced control engineering can profoundly influence a power plant’s performance and operation.

Unfortunately, due to a historically limited viewpoint of process control by electric utilities, these benefits are generally overlooked. Utilities have typically based process control decisions on obsolescence factors and technical product features, instead of on asset value that has the potential to improve the quality and availability of generated power.

Advanced automation can increase profits through: increased power plant availability, reduced cost of environmental compliance, improved efficiencies, effective information analysis and lower plant life cycle costs. In today’s market, savvy power generators are recognizing the capabilities of a plant’s control and information network and are incorporating solutions that favorably impact their bottom line.

A New Kind of Thinking

Distributed control systems (DCS) designed and manufactured before the late 1990s were proprietary, customized computer systems that used hardware and software components designed and manufactured by the DCS suppliers. Modernizing analog controllers and electronic relays to a proprietary DCS had a positive impact on power plant operations.

Nonetheless, proprietary DCS required specialized knowledge for system engineering and maintenance. In addition, custom application costs were high and getting the new control system to be functionally equivalent to the old system required significant capital and manpower resources. It also required extended outage periods. As a result, electric utilities only considered modernizing their controls when they became obsolete. When this happened, utilities invariably sought technologies with the longest shelf life and frequently demanded that DCS suppliers support the proprietary technology for 15 to 25 years after its installation.

In the late 1990s, with advances in computer technologies and the advent of open architecture DCS, electric utilities’ philosophy towards process controls started to change. As commercially available hardware and software platforms reached the reliability and capability of proprietary systems, DCS suppliers responded.

The launch of Westinghouse Process Control’s “Ovation Control & Information System” in 1997 introduced the first non-proprietary, open-architecture system built to open industry standards. Open systems, using commercially available technology from Sun Microsystems, Microsoft, Cisco, Oracle and Intel, allow power generators to remain current with rapidly changing technologies at costs significantly lower than those of proprietary technologies.

Not only does an open architecture alleviate previous obsolescence concerns, it also offers plants numerous solutions for addressing operational challenges. As utilities recognize the benefits that open architecture control systems provide for their business objectives, control modernizations are now being viewed as strategic ventures, instead of mere equipment replacements.

Using Technology to Improve Competitiveness

As the electric power industry re-invents itself for competition, managers are mapping the costs of generation and business processes, and are seeking ways to increase revenue streams and decrease operating costs. Control upgrades, whether the simple addition of a supervisory optimization package, or an expanded controls modernization program, can provide substantial payback.

Modernizing and upgrading a coal-fired power plant from analog and electro-mechanical control systems to an open DCS can provide the following performance improvements:

  • Up to 40 percent reduction in maintenance man-hours and material costs
  • A unit heat rate improvement of 1.5 percent
  • A 10 to 25 percent reduction in forced outages caused by control-related events
  • A ramp rate improvement of two percent of maximum load per minute while under load dispatch coordinated mode
  • A 10 percent reduction in unit start-up time

With proper engineering, installation and support, an open system can return a utility’s investment within two years. Further support for the benefits of open systems and process control technology comes from the Jan. 22, 2001 issue of Forbes magazine. “New control systems can lower generation costs by 7 percent” according to Joseph Garber, the article’s author.

A New Kind of Customer/Supplier Relationship

As the marketplace gains awareness of the operational and economic benefits of process control solutions, a new type of relationship is beginning to develop between process control suppliers and power generation customers. Electric utilities are soliciting the collaboration of process control suppliers to assess which automation solutions will provide the most valuable impact on a generating asset. In turn, DCS equipment suppliers are partnering with utilities to maximize the profitability and earnings potential of a utility’s generating assets.

Many plant managers are recommending strategic alliances with a smaller number of suppliers. For generators with numerous plants and facilities among their assets, partnership-type agreements will allow them to share resources, collaborate engineering efforts and standardize designs. Additionally, strategic agreements reduce the expense involved in the project bidding process, which results in decreased life cycle cost.

Improving Performance While Maintaining Investments


Installing process controls. Photograph courtesy of Westinghouse Process Control, Inc.
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Arizona Electric Power Cooperative, Inc. (AEPCO) needed to improve the availability and maintainability at its Apache Station near Cochise, Arizona. After analyzing the problem, AEPCO decided to replace the control systems on all three units with a common open architecture platform. The new control system is also expected to reduce LOI (loss of ignition), which will im-prove the quality of the ash and increase its resale potential.

Although the plant decided to upgrade with a new control system, AEPCO also wanted to maintain a recently installed man machine interface (MMI) system and related operator training. After evaluating different systems, AEPCO decided to install a Westinghouse Ovation System on the plant’s three units. The new control system will reduce plant trips, minimize maintenance costs and reduce LOI. Besides installing a new control system, Westinghouse engineers will preserve and incorporate AEPCO’s front-end MMI into the open system.

Another utility has plans to install similar open system platforms at several of its stations. It will install the Ovation System at two of its power stations and at a third station will incorporate the system’s operator interface platform. However, they will keep the existing proprietary DCS controllers. Once installed, the new control systems will have improved alarming capabilities and a common interface platform. The new system will also eliminate expensive field rewiring costs.

Handling Unique Multiple Unit Load Allocation and Dispatch

Southern California Edison Co’s (SCE) 1,020 MW Big Creek hydroelectric project is an intricate complex of dams, tunnels, powerhouses, and reservoirs tucked in the Sierra Mountains. A series of tunnels and penstocks connect manmade lakes and divert water from the upper lakes to lower lakes at the system’s nine powerhouses.


Upgraded control room at the 1,500 MW Midland Cogeneration Venture’s plant in Michigan. Photograph courtesy of Westinghouse Process Control, Inc.
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The utility initiated a modernization plan to update the controls and improve the operation of the 23 geographically dispersed units that encompass the Big Creek system. In addition, SCE wanted to network all 23 of its generating units across a wide area network (WAN) using open technology. This will provide economic load allocation of the Big Creek system.

Having selected a Westinghouse control system, SCE worked with Westinghouse engineers to incorporate a number of networking technologies into the system architecture. This links the individual networks at each location into a regional WAN. The system coordinates the control of all 23 generating units and analyzes real-time data relating to tunnel and stream flows, reservoir levels, spills, run-offs and storage estimates for regional water management and resource optimization.

An economic dispatching optimization software package manages the load from the 23 plants. In operation, the system maximizes plant profitability while operating them within their oper-ational and environmental constraints. With the new system, SCE has improved its ability to perform effective, real-time load management of its hydroelectric assets. The system was also configured to interface with a variety of existing I/O including OPTO-22 I/O, Modicon PLC I/O, and Westinghouse Q line I/O, thus saving significant project hardware and installation costs.

Addressing Limited Resources and Outage Reduction Issues

To reduce plant emissions, the Bay County Resource Recovery Facility in Panama City, Fla. decided to add pollution control equipment to its generation process. Unfortunately, its older process control system could not support any additional functionality.

Although open technology was available, a cost-effective technology to convert plant information in Bay County’s existing proprietary system to the open platform did not exist. Additionally, the plant could not afford the labor resources, schedule delays and outage time required to migrate its existing controls application to an open system.


State-of-the-art process controls are installed at the 1,500 MW Midland Cogeneration Venture Michigan plant. Photograph courtesy of Westinghouse Process Control, Inc.
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Working against a schedule to install the new equipment, but also interested in the benefits of open architecture, Bay County offered to serve as the test and development site for a Westinghouse migration tool. The tool reduces the time for converting a plant’s existing graphics, functional controls and logic codes to an open architecture platform.

In January 2000, Westinghouse and Bay County began to develop the automated tool. By March, a pilot system was ready for use. Using the migration tool allowed Bay County to install the new control and information system in two days.

The migration tool developed for the Bay County project was also used to modernize the control system for the 1,500 MW

Midland Cogeneration Venture in Michigan. Midland’s outage be-gan on a Saturday and by the Monday the plant was back in service. By the end of the week, the plant was operating at full load.

Using the migration tool developed in cooperation with Bay County allows a plant to minimize outage costs by reducing system re-engineering, re-tuning and costs associated with disconnecting and re-terminating the field wiring.

Change and evolution will continue in the electric generation industry for the near future. However, by forming new strategic agreements with their process control manufacturers, utilities can positively impact their plant operations through shared expertise, technology, responsibility and vision. Through cooperative alliances, open systems can be customized to meet specific plant needs.

Bio:

Joyce Dasch has been with Westinghouse Process Control, Inc. for 16 years and has been SmartProcess Product Manager since October 1999. Joyce has a BS degree in Industrial Engineering from the University of Pittsburgh.