Focus on O&M: Replacing Multiple Turbine and BOP Control Systems with a Single Platform
Termoyopal, a utility based in Bogota, Colombia, recently repowered its power plant at Yopal, Colombia, by replacing three gas turbines with refurbished units and upgrading the remaining two turbines. The repowering employed three GE Frame 5 gas turbine generators, which were relocated to this site from the U.S. following mechanical refurbishment. Termoyopal had successfully operated the existing units for many years and its staff were already very knowledgeable in the operation of the plant, as well as the advantages and disadvantages of their existing turbine and balance-of-plant (BOP) control systems.
The arrival of the replacement units presented Termoyopal with the opportunity to resolve issues its staff had identified with the original units, while rationalizing the control and operation of the entire plant. Termoyopal especially wanted to simplify its personnel training and parts inventory requirements, while at the same time gaining improved access to plantwide data and maintaining a high level of reliability and control. Turbine Technology Services (TTS) undertook a consolidation of a majority of the disparate systems onto a single platform. The goal was to modernize and simplify the entire plant control, increasing the available system data, while offering an interface tailored to the operators’ and maintenance engineers’ specifications for plant operations.
Beginning in the fall of 2011, TTS began the installation of what was to be the first of five turbine control, generator control, and BOP programmable automation controller (PAC)–based systems.
The original control systems for these units consisted of a mix of legacy GE MKIIs, MKIV, and third-party Modicon-based programmable logic controller (PLC) control systems. In addition, each gas turbine had its own gas conditioning skid with a PLC-based controller that was not standard between skids. To add further complication, in the neighboring gas plant that was the primary gas supply source for the power plant, Termoyopal had a primary gas-conditioning skid (for controlling the gas supply pressure and removing liquid condensate from the fuel) that also had its own PLC system that was isolated from the gas plant and power plant distributed control systems (DCSs).
With this daunting variety of control systems, Termoyopal’s maintenance personnel needed to be proficient with several programming languages and hardware platforms. They also had to maintain an inventory of spares for each system type.
System Upgrades
At the core of the system upgrade performed by TTS was Rockwell Automation’s PlantPax system, which provides a scalable architecture for easily adding process components, both hardware and software. Cybersecurity was a top priority for Termoyopal, and the PlantPax system allows for all of the Rockwell control products to be easily integrated into the plant’s security scheme. The system provided to Termoyopal was designed with multiple levels of security clearances so that each user account could be customized for secure access to the system.
TTS’s TMS-1000 control system uses Rockwell’s RSLogix5000 programming software. RSLogix5000 follows the industrial programming standard IEC 61131-3 and features the following programming languages: Ladder Logic, Structured Text, Sequential Function Chart, and Function Block. These programming tools combined with an intuitive operator interface (HMI) platform would give Termoyopal the tools to operate its power plant with much greater facility than before.
The ability to easily network all the units together also meant that all the unit data could be viewed on HMI stations either locally or remotely (Figure 1).
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| 1. Unification. The upgraded HMI allowed a unified view of the upgraded system, such as the gas fuel system with electric valves shown here. Courtesy: Turbine Technology Services |
Execution
The plant upgrade began with the GE Frame 6B unit. The plant was conducting a mechanical overhaul of the unit, and in order to minimize the outage, Termoyopal mobilized TTS technical advisors to begin instrumentation upgrades and an on-base unit rewire while the mechanical works were still in progress. As part of the system upgrade, TTS provided various instrumentation enhancements, including a performance monitor instrumentation package and software algorithms to calculate unit efficiency. With this information, Termoyopal would be able to assess unit historical performance and better determine when to schedule unit maintenance based on OEM recommendations. Other instrumentation upgrades were installed to improve available data from the unit or improve reliability, including new flame scanners and transmitters on the lube oil and hydraulic oil circuits.
TTS then upgraded each of the Frame 5 units, replacing the existing turbine control system and generator excitation and protection systems. TTS performed the same on-base rewire and instrumentation upgrades as on the Frame 6. Two of the units were converted from liquid-only operation to dual fuel with the addition of gas fuel and fuel purge systems. This work was carried out while in the Sulzer Turbo Services Houston facility, where a complete mechanical and electrical overhaul and rehabilitation took place. The new gas fuel systems included state-of-the-art all-electric stop and control valves, which greatly simplified installation and gas fuel operation.
All the units were equipped with a TTS TMS-1000S control system, the simplex version of the standard TMS-1000 turbine control system, and aTMS-1000G digital generator control and protection system. The TMS-1000S is fully integrated with the TMS-1000G through both hardwired connections and communication connections using industrial standard communications protocols, such as Modbus, to facilitate easy integration of functions and the collection and presentation of turbine and generator operational and diagnostic information.
The TMS-1000S is built using the L72 ControlLogix processor. This allows the TMS-1000S to be flexible in the ability to accept a wide variety of signals, including vibration with API 670 compliant vibration modules. The TMS-1000G consists of a digital AVR, digital generator and transformer protection relays, synchroscope with integrated check-synch, automatic synchronizer, bus undervoltage relays, and a generator multifunction meter.
Time synchronization hardware and software was provided to integrate with the existing GPS time source. All components in the system were synchronized to a single source to extend the usefulness of the historical data displayed on the HMI.
For machine protection, a Rockwell Automation XM system was installed for both independent electronic overspeed and complete train vibration protection. Although this system is fully independent, a DeviceNet communication link allows complete integration of the system variables into the TMS-1000S. Detailed vibration and overspeed screens were provided on the HMI for operator use.
Where possible, such as for the local gas skids, remote I/O blocks were located close to the equipment, and data was sent to the central controller over a redundant ControlNet network. The networks utilized both copper and fiber media, depending on distance and plant location of the I/O modules. This approach eliminated the need to run large amounts of wire from the base controller to these modules, which provided a significant saving in material and installation costs.
As part of the plant control system upgrade, TTS provided a dual-language, multi-unit HMI. This HMI was server-client based, allowing for additional HMIs to be easily added and integrated into the HMI system as subsequent plant units were upgraded. Termoyopal also wanted to make full use of the additional data acquisition, storage, and presentation capabilities provided by an integrated digital system. To accomplish this, TTS provided a separate historian and worked with plant personnel to build structured Excel reports that automatically read the data from the HMI historian.
The standard turbine/generator control system graphics were also modified and augmented to meet Termoyopal’s needs as identified by site personnel. Operators now have the ability to go online with each PAC to view and troubleshoot logic in real time. Reports can be generated automatically, minimizing the time it takes to create operator logs. Trends are available in both real-time and historical format for system troubleshooting and maintenance. There are dedicated screens for maintenance tests, I/O screens by module, and system diagnostics. The new control platform helped an already well-informed and knowledgeable staff become even better at the operation and maintenance of their plant.
Several other upgrades were also performed, including:
■ Connection of the system to the Eaton/Cutler Hammer motor control centers (MCCs) on site to allow for the monitoring and storage of MCC starter information and for the presentation of this information on the HMIs.
■ Integration of the existing plant GPS into the control system to allow for synchronization and real-time stamping of data and events.
■ Addition of Modbus communications to the gas plant, which allowed data from the gas supply skid to be displayed in the gas plant’s DCS.
The base control and protection system hardware and software were essentially the same for all five units. This meant that plant engineers and operators could learn about all the units following a single training course. Training was provided to plant personnel on an ongoing basis as each individual unit was upgraded and integrated into the system. Because the BOP system control was also implemented using the same basic hardware and software, only minimal additional training was required to allow for operational familiarity with these systems.
Replacing its aging equipment and unsupported software platforms allowed Termoyopal to realize some significant benefits. These included:
■ Significantly reduced overall inventory and individual component costs.
■ Reduced long-term personnel training costs.
■ Improved equipment system data acquisition, analysis, and storage tools.
■ Improved operational and engineering productivity.
■ Improved system reliability and availability.
■ Significantly reduced overall cost of ownership. ■
—Chris Crowell is project engineer with Turbine Technology Services.