Ovation Users’ Group, meeting highlights

Controls platform expands envelope of services, functions

The numbers are tough to defeat. During the five-year period 2000-2004, around 200,000 MW of gas-fired capacity was installed in the US. The expected life of the control systems for those facilities is far less than the physical components—the steam turbine, for example—considering the dizzying progress with digital technology and general obsolescence characteristics of digital hardware. This explains why so many combined cycles and peaking gas turbine/generator plants have been undergoing control system retrofits in recent years.

This issue offers case histories involving control upgrades/replacements on LM5000, LM2500, Frame 6B, and FT4 engines. In the recent past, CCJ has published several articles focused on control system improvements—including upgrade of overspeed protection on legacy Westinghouse (Siemens) and GE machines, alarm management specs for replacement control systems, link-up of disparate legacy control systems at a cogen plant, etc. It’s easy to access other articles on the subject of interest using the search bar at the top of this page.

It’s no secret that Emerson Process Management’s Ovation platform is involved in a significant volume of this retrofit activity. A key reason is that the distributed control system (DCS) is morphing into a plant knowledge system, with enhancements focused on adding functionality and organizing the user experience (Fig 1). At the most recent meeting of the Ovation Users’ Group conference, Emerson’s Glen Wagner discussed the expanded role of the main automation contractor (MAC) for a project, as distinct from a DCS supplier.

Ovation UG Fig 1

Whereas the traditional vendor retrofit services might be proposal, hardware, engineering, training, and field support, MAC additionally includes scope definition, installation design and drawings, full-scope installation and commissioning, high-performance control room, and integration of plant drawings into Ovation. It’s a variation on the single-source supplier model: A turnkey controls and knowledge platform supplier, or a lifecycle partner, rather than vendor type of relationship.

Retrofits often have multiple motivations. Emerson’s Laurence O’Toole and David Cicconi opened their presentation showing how many fossil units have changed operating profiles. In many areas, a small coal-fired unit (Fig 2) will be “filling in” around must-take renewable assets and less-expensive gas-fired assets. Meanwhile, many gas-fired combined cycles have dramatically increased their capacity factors over the last few years. Plant control systems have to provide a new level of flexibility to meet these challenges.

Ovation UG Fig 2

O’Toole and Cicconi illustrated four broad themes for gas-turbine (GT) retrofits: (1) a retrofit experience base that now includes most, if not all, control system OEMs one might find in a gas-fired plant today, (2) partnerships with independent GT service providers to offer enhanced solutions and more flexible service agreements, (3) product enhancements for overspeed protection, vibration, and overall turbine health monitoring; and (4) nine GT controls-retrofit project briefs. One of those projects, the subject of a separate presentation with Dan Jones, Kansas City Power & Light Co, recaps Ovation retrofits for 19 turbine control and excitation systems, with a focus on replacing two 7EA DLN-1 Mark V control systems at KCP&L’s Hawthorn Generating Station.

More and more today, controls retrofits include a makeover for the operator graphics, or the human-machine interface (HMI). Clint Vanderford, NV Energy, illustrated in his presentation the high-performance control room for the Ft Churchill station retrofit. Although not a gas-turbine-based plant, the characteristics, objectives, and lessons learned of the HMI would likely be similar, namely:

    • Reduce alarm overload and operator alarm fatigue.

    • Adopt a graphical hierarchy for different operator skill levels, such as clear summaries for veterans and P&ID graphics for step-up operators.

    • Use gray scales rather than color to avoid distractions and improve situational awareness and response.

    • Work from a written alarm philosophy (one version of the truth) and focus on alarms during logic review.

    • Design graphics from the beginning; they drive important logic details.

    • Don’t neglect ergonomics, such as furniture details and selection.

    • Involve the operators early in the process and expect to resolve conflicting opinions and preferences.

Other important learnings, summarized here, include the following:

    • Emerson is developing models and algorithms that will be embedded in Ovation, so one single platform and integrated database can be used for control and simulation.

    • Emerson now offers a digital generator controller (DGC) as part of Ovation that builds on its experience with exciter control retrofits.

    • The recent release of Ovation 3.5.1 includes special features important for aeroderivative GT control.

    • Greater intelligence afforded by wireless and electric actuators is available for all the critical valves in the gas-fired plant.

    • Cybersecurity solutions in part depend on a facility’s compliance obligations under NERC CIP, keeping in mind that compliance is not security.

    • Emerson’s System Backup and Recovery (SBR) product can help you navigate through various scenarios and options and organize your backup files.

 

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