St. Johns River Power Park

Owner: JEA and Florida Power & Light Company

• Electrical Output 640 MW per unit
• 2 Foster Wheeler coal fired boilers
• 2 GE tandem compound turbine generators

Background

St. Johns River Power Park (St Johns) is located in Jacksonville, Florida on the St. Johns River. The plant consists of two coal fired Foster Wheeler drum boilers and two General Electric turbine generators, each with an output of 640 MW. The boilers are able to burn a wide variety of coals from all over the world, and they can burn up to 20% petroleum coke. The main steam conditions are 2,400 psig and 1,005 degrees F. The units were placed in commercial operation in 1987 and 1988. JEA (formerly Jacksonville Electric Authority) and Florida Power & Light jointly own SJRPP.

St Johns believed it was necessary to modernize the plant’s aging control systems in order to meet a changing set of operating objectives and to provide plant operators and engineers with better tools. In addition, there were numerous components of the old system that were no longer available in the market place.

Modernizing systems of this scale is not a simple task. It requires extensive up-front planning to develop a set of guidelines, requirements and product specifications. St Johns management at first considered utilizing an architect engineer for this work, but the time and expense could not be justified. Rather, it was decided to employ Metso to do a thorough study of the existing control systems and then propose a solution that would meet the new objectives of the plant. From this study a work statement was created that led to a contract to modernize the plant with a new maxDNA automation system.

Project Goals

The St. Johns plant management established clear objectives for the project:

• Upgrade the control system to the latest technology
• Improve unit response on Automatic Generation Control
• Integrate new turbine controls
• Integrate new burner management system
• Optimize the operation of new low-NOx firing system
• Convert to all soft control and phase out the BTG Board
• Provide hands-on training for operators before startup
• Minimize outage time for installation
• Complete the project in ten months

The Direct Energy Balance (D-E-B) control strategy was utilized, minimizing the time required for operator training, checkout, and control system tuning. Since overall unit performance was a very important requirement, the coordinated control strategy was reviewed and improvements were made to enhance unit MW response. Existing termination cabinets were retained, minimizing the disruption to field wiring.



Metso’s Scope of Supply

Metso provided a turnkey solution, taking prime responsibility for the design, installation, and startup of the new control system and field equipment. Demolition and removal of the old system cabinets, as well as new field wiring where applicable was a part of the contract. Prior to the award of the automation system contract, Metso performed a comprehensive study that established the scope and key engineering details of the project.

Under the turnkey contract, Metso’s scope of supply included the following:

• D-E-B/400 Coordinated Boiler-Turbine Control
• maxDNA Version 4
• maxDPU4F
• maxPAC I/O modules
• Interface to Burner Management System
• Interface to Turbine Control System – Modbus TCP
• Interface to Data Acquisition System – OPC
• New Electric Drive Units
• New Pulse-to-Pneumatic Converters
• Operator Training Simulator
• Operator and Maintenance Training
• Remote maxVUE
• maxEDC – Excel Dynamic Connection
• System Engineering, Configuration, and Graphics
• Construction and Installation Services
• Startup and Commissioning Services

System Design Features

The footprint of the new system is smaller than the old system, freeing up valuable floor space for future plant needs. The new system was designed for ease of installation. Existing termination cabinets were kept in place. Power distribution was designed for reliability and ease of maintenance.

The controls configuration was engineered to provide a smooth transition from the old system. All of the important database parameters from the old system were imported into the new system using maxDNA engineering tools. Tuning constants were imported, allowing the unit to run on automatic as soon as it was on line.

Plant operators provided extensive input to the design of the operating graphics. The project team worked together to determine project standards, display layouts, and features to be included. Navigation was designed to be intuitive for the plant operators. Security features and operator aids provided a safe and easy transition to soft control. The graphics reflect the state of the art in HMI science.

The Unit Master display, shown below, provides the plant operator with all of the vital information necessary to run the unit. From this display, the operator can select the mode of operation, see trends of key variables, enter ramp rates and load limits, and see the status of every major piece of control equipment. Navigation buttons take the operator to any related display or trend. Alarms are highlighted by colored borders. Tool tips provide descriptive information.




Project Schedule

After discussing the objectives of the project with Metso, St. Johns decided to proceed with a study. The study report addressed all aspects of the project and included the design details necessary to define the scope. This was completed in a little less than two months. The study was completed just in time for budget approval, allowing the project to be funded without delay. Once the funding was in place and the contract signed, the system was designed, built, and tested in Metso’s factory in five months.

The installation of the first system was completed during an eight week outage. The total duration of the project from the time the study was started to the time the unit was running on the new system was just over ten months.

Field Equipment

During the study, all of the field equipment was evaluated to see if it was suitable for use with the new control system. The plant had been replacing transmitters and thermocouples as part of a maintenance program. The electric drive units were in need of replacement. The plant selected Beck drives to replace the original single-phase and three-phase drive units. Metso supplied and installed 27 new Beck drives per unit as part of the turnkey project. An innovative interface using HART allows the Beck drives to be operated with a conventional 4-20mA demand signal, while receiving position feedback, alarms, and diagnostic information over the same existing field cable. No new cables were needed.

The existing spray valves used for steam temperature control were equipped with Leeds & Northrup Pulse-to-Pneumatic converters, operated by Pulse Adjusting Type (PAT) outputs from the control system. PAT provides fail-in-place operation, a feature that St. Johns wanted to retain. Metso supplied 15 new Pulse-to-Pneumatic converters per unit with the same PAT interface, eliminating another potentially weak link in the control system.


Load Response on AGC St. Johns Unit 2 with D-E-B/400

Installation

Metso prepared detailed construction specifications that were used to obtain competitive bids for the installation. Responsibilities were clearly defined from the beginning of the project, and a strong sense of teamwork allowed Metso, St. Johns, the installation contractor, and the other equipment suppliers to achieve all the schedule and cost targets.

St. Johns personnel were able to install many of the new Beck drives prior to the outage, with the remainder installed by the installation contractor. This saved outage time.

Crews removed the old control system cabinets and installed new maxDNA cabinets during the first week of the outage. System I/O was connected from existing termination cabinets to new I/O cabinets.

Unit Performance Results

Load control and economic dispatch are critical requirements for St. Johns. D-E-B coordinated control, including the Plant Constraint Coordinator algorithm, was employed for the specific purpose of achieving maximum response from the generating unit. D-E-B maintains boiler-turbine balance at steady load, and also provides for sustained load ramps that proceed linearly to a conclusion despite changes in fuel quality, turbine valve characteristics, or boiler operating conditions.

The maxDNA system uses special algorithms that have been refined over four generations of D-E-B control. The key concepts used in the D-E-B control strategy include:

• Pressure Ratio
• Demand Limit Regulator
• Heat Release
• Energy Balance Calculation

Outstanding results were achieved at St. Johns using the new controls for Automatic Generation Control (AGC). The chart above shows the linear load response over a 12 hour period while following a load demand signal and performing area regulation.

Training Simulator A very important element of the project was an operator training simulator that allowed operators to be trained on the new ‘soft’ controls prior to using them to operate the unit. The simulator capitalizes on the Software Backplane architecture and Virtual DPU capability of maxDNA. The simulator provides St. Johns with several benefits: an effective means of operator training on the new boiler control system, burner management system, and turbine control system, resulting in a smooth transition to soft control. a tool to improve operators’ skills, improve operating procedures, and test new control strategies the ability to perform post analysis of events and train operators to avoid similar future events The simulator uses the same graphics and the same control configurations that are used on the unit control system. Process models developed by Metso are used to simulate the boiler, turbine, and other plant equipment. The simulator has Pause, Resume, Snapshot, and Reset functions. Snapshots can be saved and used later for initial conditions. The instructor can initiate simulated equipment malfunctions in the plant. The simulator was delivered to the site prior to the outage and used to train plant operators during the outage.