The case for an open control system

Kevin Kochirka, Consulting Application Engineer at ABB Inc., made a case for power plant operators to choose vendors who offer an open control system based on his experience working at Pacific Klamath Energy Cogeneration Plant. The plant has two Siemens 501 FD3 CTs (Base Load Combined Cycle), one Alstom Steam Turbine. For peaking generation it has two Pratt Whitney FT8 Twinpacs (Simple Cycle) with an SCR ‐ Anhydrous Ammonia.

In a paper presented at Power Gen International 2014, he along with plant staff argued that power plant owners have long been interested in a more‐open system that would enable them to view live system data and quickly respond to process issues. Below are excerpts from their presentation:

“Owners and operators of Pratt & Whitney FT8 turbines are now facing the decision of how best to upgrade their turbine control systems, and should realize they have new options in the form of third party, open systems.  These solutions provide the owner/operator with the tools and data necessary to become a self‐maintainer: troubleshooting, tuning, repairing and improving independently.

There are some good reasons for a turbine original equipment manufacturer (OEM) to employ this closed‐system approach: it prevents end‐users from altering their products, minimizes the risk of unauthorized modifications and ensures consistent operation of the installed base of equipment. 

However, by locking their control system design and configuration inside the black box, they put their customers at a significant disadvantage. It could be said that they have created a captive customer base, held hostage to the OEM’s offering. Customers are forced to rely solely upon the OEM for troubleshooting, service and parts; regardless of the time, cost or quality issues. It’s readily apparent that closed control system benefits accrue almost exclusively to the manufacturer, and typically at great cost and inconvenience to their customers.  

For the equipment owner/operator, the closed‐system approach creates a recurring set of roadblocks to improved reliability and availability. They cannot quickly diagnose or respond to problems without open access to system data and troubleshooting tools. Essentially, the owner/operator is prevented from taking full “ownership” of their turbine.

Specific to older FT8 turbines, HMI hardware failures are an additional contributor to poor reliability and availability. Because of the “black box” design and OEM‐customized components, it is impossible to make computer repairs quickly. The equipment typically has to be returned to the OEM for service and updates. While that server or client is out for repair, the generating facility must adjust by relocating one of the remaining computers or changing their work flow. In the meantime, they have the additional risk of lost control system redundancy, which further erodes reliability.  

For power generators, the greater reliability and availability enabled by open control system architecture equates directly to greater profitability. At peaking power plants, operators of FT8 turbines are required to bring them online as needed and at a moment’s notice. The machine might only be required to run for 30 minutes and be online in 15 minutes.  In this scenario, starting reliability is of paramount concern.

Independent Power Producers (IPPs) typically enter into agreements with some sort of liquidated damages for failure to meet requested demand, as well as possible bonuses for having a high reliability/availability factor.  With a solid, open control system and the resulting improved reliability of the plant, IPPs can confidently enter into more aggressive and, thereby, more lucrative contracts. The higher the reliability and availability the IPP can guarantee, the greater the premium their power commands.  

Utilities have a different profitability picture. Some rely on IPPs as a backup and pay the premium just discussed. Others have their own peaking generation assets. Given the chance that the utility’s peaking FT8s will not start when needed, it’s common to have multiple turbines as backup. With the greater reliability created by an open control system, utilities can confidently reduce the redundant assets with considerable savings or, conversely, have more peaking power reliably available.

Furthermore, these units are often becoming more than peaking units, as natural gas continues to become more attractive versus other fuel sources.  In short, these units may now be scheduled to run far more often, and longer, than originally expected, which makes their reliability and availability that much more important to the power generator’s profitability.

Beyond the reliability improvement and resulting profitability enhancement, owners of FT8 turbines can realize a list of additional benefits by replacing their current, closed‐architecture control system with an open‐architecture alternative.  

At the Klamath plant the following were achieved as a result of an open control system:

·        Combination of displays for a common operational display

·        Combination of displays for a common operational display

·        Customize a full plant overview

·        Common display for start permissives, driveback, shutdowns and trips

·        Displays Monitoring all process parameters

·        Enhancements to protections

·        Ability to see all controllers interacting

·        Modification to Thrust Balancing Valve

·        Combined the Ammonia PLC controls into the DCS

·        Combined the Evaporative Cooler & Water Wash PLC into the DCS

·        Integrating Non-OEM Controls with Pratt &Whitney FT8 Turbines