|For utilities and IPPs operating older gas turbines, the superior reliability, availability and safety resulting from the application of open control systems equates directly to greater unit profitability. Photo courtesy of ABB.|
By Ed Dupre, Camilo Lopez and Kevin Kochirka, ABB Inc.
Hundreds of gas turbines (GTs) first installed between 1990 and 2005 will be ready for an update or replacement of their original equipment manufacturer (OEM) controls between 2013 and 2020. Turbines of even older origin will be ready for their second controls upgrade in the same time period. Owners and operators of many OEM-supplied gas 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 open control systems provided by a third party. These solutions provide the owner/operator with the tools and data necessary to become a self-maintainer who can troubleshoot, tune, repair and make improvements independent of the turbine manufacturer. In addition, the third party open system platform is not just limited to the gas turbine application – it is also frequently found controlling the rest of the plant’s processes. This allows the user to integrate and consolidate overall control, protection and communication infrastructures, providing significant benefits in the areas of plant performance and cost effectiveness.
In this article, we will discuss:
- Limitations imposed on owners/operators by “black box” (closed architecture) control systems
- Enhanced reliability, availability, safety and profitability benefits using open control system
- “Core competency” advantages of open system suppliers
BLACK BOX LIMITATIONS
OEM gas turbines typically come with a proprietary “black box” control system that makes it impossible for their owner/operator to troubleshoot, maintain or improve the system by themselves. There are some good reasons for a turbine 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 and create a captive customer base, held hostage to the OEM’s controls and service offerings.
Customers who retain OEM controls are often forced to rely solely upon the OEM for troubleshooting, service and parts, regardless of time, cost or quality issues. It’s readily apparent that closed control system benefits accrue almost exclusively to the manufacturer and can frequently create great cost and inconvenience for the GT owner, not only in terms of direct costs, but also in lost generation opportunities.
|Gas turbine operators can benefit greatly by considering the many advantages of relying on a third-party open control system. Photo courtesy of ABB.|
For equipment owner/operators, the closed-system approach creates a recurring set of roadblocks to the improvement of unit reliability and availability. They cannot quickly diagnose or respond to problems because they lack access to system data and critical troubleshooting tools. Essentially, owner/operators are prevented from taking full “ownership” of their turbine. For example, older HMI hardware failures contribute to poor reliability and availability. Because of the black box design and OEM-customized computer components, it is impossible to make repairs to outdated computers and to have upgrades implemented 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 reallocating 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.
These types of computer issues can also create safety risks. At the facility of one independent power producer, the client computer in the control room failed and had to be sent for repairs, which typically took about four weeks. With the normal client unavailable, an operator had to work from the HMI at the server location adjacent to the turbine. This put the operator within one foot of 480VAC distribution breakers and directly in front of the 13.8 kV generator circuit breaker, within a high hazard arc-flash zone. Safety practices at this plant required the operator to leave the arc-flash zone during certain events (e.g., generator breaker opening or closing). This made unit troubleshooting quite difficult, because it forced the operator to exit the structure that housed the equipment being investigated.
All of the above is made even more problematic by the fact that many gas turbines are located at significant distances from the main control room, or even in an entirely different facility, and thus are normally unattended. Client failures or communication failures in proprietary control systems can then become extremely inconvenient and costly to solve.
THE FREEDOM OF OPEN SYSTEMS
Today, many third-party providers offer open access to their control systems. For the first time, GT owners can see live data flowing across the logic and use it to make faster, better-informed decisions regarding turbine operations. They are able to rapidly identify issues preventing turbine starts and make repairs, adjustments or workarounds to rectify the issue and resume power generation. Operators are also able to monitor and tune their turbine control systems, identifying potential turbine issues in advance and taking corrective action proactively.
In the closed-system environment that most OEM-controlled GT owners work in, this type of fast response is simply impossible. They are often forced to rely on remote telephone support from the OEM. Repairs are delayed while the appropriate support person is reached. Once in contact with the support person, there are additional delays as the plant representative describes the issue. Since the plant representative doesn’t even have access to live control data, they are frequently dispatched to measure inputs at a device in the plant and report back via a return phone call. Cycling through any problem using this old-school problem-solving technique can obviously take a long time and incur significant service costs and down-time generation losses.
|Centralized unit operations can be a major improvement on the control systems provided from a gas turbine’s original equipment manufacturer. Photo courtesy of ABB.|
The open system approach also reduces issues related to clients and servers. The ability to use standard components that can be repaired or upgraded locally and to easily update or patch software makes it possible to quickly repair or replace a troublesome computer. This ensures that the appropriate complement of HMIs will be available at nearly all times. It also reduces or eliminates the need for operators to ever have to work inside an arc-flash zone or to remove themselves from hazardous control system areas during crucial operating and troubleshooting exercises.
A MORE PROFITABLE APPROACH
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 gas turbines are required to bring them online as needed and at a moment’s notice. The unit might be required to be online in just 15 minutes and then run for only 30 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 therefore 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 peaking premiums discussed above. Others have their own peaking generation assets. Given the chance that the utility’s peaking GTs 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 occasional 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.
A BENEFICIAL LONG-TERM PARTNERSHIP
Beyond the reliability improvement and resulting profitability enhancement, owners of gas turbines can realize many additional benefits by working with a supplier that offers open control systems as their core competency. The major benefits include:
- Collaboration: OEMs offering only closed systems can be less sensitive to the specific needs of the owner/operator and are typically unwilling to innovate at that level. The GT OEMs know they have a captive market and can therefore offer only their own standard solutions. Absent any competition, they have no pressure to offer their solutions at a reasonable price. On the other hand, open system vendors realize they must actively compete to earn their customers’ business. They understand the need to listen to an individual customer’s specific issues and respond with targeted solutions. These third-party suppliers appreciate the need to innovate at such a level and are eager to demonstrate their ability to cure longstanding and troublesome operational issues.
- Independence: Open systems are designed to allow owner/operators to take full responsibility and ownership of their asset and be self-maintainers of that asset. This concept is at the core of the open system supplier’s value proposition, so a full set of troubleshooting tools come standard with the product. Plant staff can observe high-resolution, real-time and historical process trends, enabling them to identify issues that can be quickly investigated and, if necessary, remedied independent of OEM support and its inherent limitations. Moreover, this data can form the basis of an improved asset management program, enabling more predictive and less routine or reactive maintenance.
- Latest Technology: The gas turbine OEM’s main focus is the machine itself, not the control system. It is not uncommon for them to rely on external low-cost PLC solutions for addressing their control needs. In this situation, the ability of the turbine OEM to dictate the functionality and performance specification of the control system they supply is limited. Their main interest is ensuring that the chosen technology allows for the locking or “black-boxing” of their control algorithms to support their financial strategies. The third-party open system provider has a greater focus on the control system capabilities, as DCS technology is at the core of its business. These companies invest heavily in this area to ensure they are always positioned in the vanguard of their industry in terms of performance, safety, functionality, reliability, flexibility and openness. The end result is a superior control system supported by one single vendor with ownership fully transferred to the customer.
- Customization: Owner/operators can choose to customize the HMI graphics in a variety of ways, either during or after the upgrade. As one simple example, device tags can be changed to names that are more meaningful to the plant staff. In most cases, control room personnel manage multiple systems, each with its own graphic standards or conventions. With an open system, the owner/operator can specify that the new control system graphics match existing systems’ graphics. This simplifies the unit operator’s job, reduces operator errors and enables faster training and operator response.
- Security: Third-party control providers can also ensure that NERC-CIP requirements can be met and offer services that help GT owners/operators implement comprehensive security programs. These issues can be considered and addressed during the upgrade project or process.
- Lifecycle management: GT OEMs typically do not offer an elegant, cost-effective migration path for their control systems. “Rip-and-replace” is their usual approach to keeping the control system current. Many third-party providers follow a lifecycle approach instead. They provide a stepwise evolutionary path for control system upgrades. This allows the owner/operator to maintain a state-of-the-art system over the entire turbine lifecycle while minimizing the cost and risk to the unit that are frequently associated with rip-and-replace upgrades. Owners/operators are also not locked into buying upgrades or add-ons from the OEM. New technology that could add a desired capability can be readily interfaced with an open control system architecture (e.g., optimization software, new and improved field devices, etc.).
- More responsive controls service: Some GT OEMs are clearly focused on the sale and installation of the original equipment. Lifecycle services are an afterthought, especially when it comes to the control system. As described earlier, some GT owners/operators are well-acquainted with the painfully slow and aggravating telephone-tag style of remote service. Onsite service is often provided by an OEM-authorized service representative. For both phone and on-site service, it is common to have different service representatives with each call. Lacking familiarity with the specific facility and turbine, each new service representative has to be brought up to speed on the equipment, adding time to each service call and delaying critical repairs. Open-system providers are more service oriented and have organized their support resources to better meet customer needs. They have technicians who are on call and located throughout the service region in order to respond more quickly and in person when the situation requires. Many are willing to dedicate individuals to a specific plant. Simply put, third-party control system providers realize that they need to support their controls customers every day. This mindset is evident in their control system’s evolution programs, comprehensive set of service offerings and overall responsiveness to customer needs.
While such supplier-sourced service advantages are very real, turbines that are equipped with an open system provide another truly significant advantage. A well-designed open control system provides access to live GT operational data and capable troubleshooting tools. Result: Many local operators are typically able to troubleshoot and resolve issues without external service intervention. This significantly reduces the time and cost of problem resolution and provides another critical operational advantage.
ELEMENTS OF A CONTROLS RETROFIT
Open control system (OCS) upgrades and replacements can cover every instrument and control aspect of a GT unit. This includes the control and protection hardware and software elements (PLC or other), user HMIs, panels, cabinets, input/output, fuel and other valve actuators, generator excitation system, condition monitoring sensors and other elements of the instrumentation and controls for a GT unit.
NEW OPPORTUNITIES FOR GT OWNERS
Many GT owner/operators already have, or soon will have, a pressing need to replace OEM control systems because of the obsolescence of the HMI clients and servers as well as reaching end-of-life for critical actuators and instrumentation. They face long delays as these items are repaired and/or updated, and are at greater operational, safety and profit risk while these assets are unavailable. The reduced reliability of their generation assets will prevents IPPs from bidding on more lucrative contracts and increases their chance of paying penalties for failing to meet existing contractual requirements. Utilities may be forced to carry additional equipment, overhead and operating expenses for redundant assets in order to ensure that they have sufficient generation capacity when one or more turbines fail to start. Even operators with recently installed units who have not yet experienced the pain of unreliable older equipment are still seeking third-party, open-architecture control systems. They are frustrated at being held captive by the turbine manufacturer’s controls. They are eager to achieve a higher degree of plant controls integration and/or consolidation, have access to useful live data, respond on their own to issues and take true ownership of their turbine and its control system.
Open control system upgrades and replacements have been field proven to increase availability, reliability, safety and profitability versus OEM and other black box control solutions because the owner/operator is provided with the tools and data necessary to become a self-maintainer who troubleshoots, tunes, repairs and improves independently from the GT’s OEM. Regardless of the reason for upgrading the control system, GT operators can benefit greatly by considering the many advantages of relying on a third-party open control system.
Power Engineerng Issue Archives
View Power Generation Articles on PennEnergy.com