Instrumentation & Controls

Optimizing combustion control is critical to reducing emissions and increasing plant operating efficiency, particularly for fluidized bed combustion (FBC) boiler plants burning biomass fuel that has unpredictable moisture content. The secret: measuring actual energy flow.

Handheld smart devices providing custom applications and Internet access at the touch of a virtual button are common today. Hidden beneath their touchscreens is a global network of digital technologies that respond to each command. Will these familiar commercial technologies and apps make their way to industrial digital control systems?

Asset management means different things to different people. But it boils down to converting raw data and observations about equipment and components into information and knowledge that is then used, propagated, and shared by workers and digital components to manage performance. Nuclear plants have special asset management needs, given the level of their safety, reliability, and regulatory requirements.

The enhanced plant performance achieved at the 1,477-MW Morgantown Generating Station shows the value of model predictive control in conjunction with intelligent distributed control algorithms. This project update looks at how the project team moved from ramp rate improvements to reducing tube metal temperatures to improved component life.

Control loop performance-monitoring software can help to improve loop performance at electric power plants by automatically collecting data, assessing several aspects of loop performance, and providing the results in reports and user interfaces.

The consideration of power supplies has become critical to the success of converting analog instrumentation and control systems to digital control systems (DCSs). Careful planning is particularly necessary for nuclear power plants, where instrumentation systems are required for safely shutting down a reactor, mitigating the consequences of an accident, and performing post-accident analysis.

One of the great successes of the power generation industry over the past two decades has been the significant increase in nuclear plant reliability and other performance standards. However, there is reason to be concerned that the design, operation, and maintenance practices used by the current fleet of plants do not leverage all the possible advantages from a digital controls upgrade. Perhaps past success is the biggest barrier to future success.

Asset “virtualization” extends and combines the technologies of 3-D visualization and virtual reality to a new, practical level for the life-cycle management of power industry equipment. All pertinent data for a component, subsystem, or plant is associated with, stored, and accessed through as-built 3-D digital models of the actual plant that are constructed using laser scanning techniques.

When adding, modifying, or upgrading a system, many critical infrastructures conduct a factory acceptance test (FAT). A FAT includes a customized testing procedure for systems and is completed before the final installation at the critical facility. Because it is difficult to predict the correct operation of the safety instrumented system or consequences due to failures in some parts of the system, a FAT provides a valuable check of these safety issues. Similarly, because cyber security can also impact the safety of critical systems if a system is compromised, it makes sense to integrate cyber security with the FAT.

Recent advances in water laboratory instrumentation—from improved sample conditioning to advanced online instruments—have reached the market. Here’s a look at the equipment you’ll find in the best-equipped power plant laboratory this year.

In November 2008, a central Texas utility commissioned HPI, a full-service turbomachinery design and construction firm based in Houston, to perform a major upgrade of its plant’s power distribution and turbine control systems.

Neural networks have already found practical application in many plants, and recent advancements in artificial intelligence promise to shape the design of the next generation of power plant supervisory controls. Will future plant operators be fashioned from silicon?

Tightly managed grids require combined-cycle plants equipped with power block controls that can quickly respond to automatic generation control signals with minimal error. K-Power’s successful controls upgrade demonstrates that that goal—and more—is achievable.

Modern distributed control system platforms can provide many tools to capture best operating practices and automate them. This case study shows the steps taken to automate a hypothetical simplified feedwater pump system for a combined-cycle power plant. It describes a combination of controls automation strategies and human-machine interface techniques designed to increase the overall level of automation while improving ease of use.

At Morgantown Generating Station, plant personnel used innovative methods to combine model predictive control with distributed control system–based process control algorithms to improve waterwall temperature control and main steam temperature control and to enhance unit ramp rate capability. The previous heat rate and NO_x optimization performance gains were retained. Focusing beyond basic loops of feedwater, air, and O₂, the project considered issues such as PID controller override configuration and limitations. The techniques used to overcome these challenges improved unit ramp rate capability beyond any previous unit performance.

Development of Vogtle Electric Generating Station Units 3 and 4—the first new nuclear power plant units in the U.S. in decades—has generated considerable excitement. The next generation of nuclear plants, represented by these units, includes at least two major improvements: the use of passive safety systems and a reliance on digital control systems. The latter represents a gigantic leap in modernization and a fundamental change in control of the plant.

The Electric Power Research Institute has developed a pair of diagnostic tools that combine and integrate features from multiple sources of plant information. The Diagnostic Advisor and the Asset Fault Signature Database will improve diagnostics for and troubleshooting of equipment faults by providing a holistic view of the condition of plant equipment.

A common concern for gas turbine power plants is treating exhaust gases to comply with laws restricting pollutants present in the gases that are emitted into the ambient atmosphere. The challenge for designers is to control the exhaust gas operating temperature within a range that maximizes performance of the oxidation and reduction catalysts.

One important factor in power plant control system performance is the response time of the process measurement used in the control system. The response time of boiler steam temperature sensors and thermowells is examined, as is those sensors’ and thermowells’ effect on desuperheater temperature response time and, therefore, steam temperature control performance.

In the 1950s, temperature-equalizing columns were commonly used in steam drum differential pressure–based devices for measuring water level. However, these columns are problematic because a portion of the reference leg can flash to steam on a pressure decrease (load increase), and this will result in a temporary, false, high-level measurement, which adds to the swell effect. The columns can also result in measurement inaccuracies. It’s time to replace these antiquated instruments with a more modern reference leg.

Luminant used remnants of the ill-fated Twin Oaks and Forest Grove plants (which were mothballed more than 30 years ago) to build the new two-unit 1,600-MW Oak Grove Plant. Though outfitted with equipment from those old plants, Oak Grove also sports an array of modern air quality control equipment and is the nation’s first 100% lignite-fired plant to adopt selective catalytic reduction for NO_x control and activated carbon sorbent injection technology to remove mercury. For melding two different steam generators into a single project, adopting a unique and efficient “push-pull” fuel delivery system, assembling a tightly integrated team that completed the project on time and within budget, and for completing what was started almost four decades ago, Oak Grove Power Plant is awarded POWER magazine’s 2010 Plant of the Year award.

Given delays and cancellations of new generating capacity, pushing the existing power generation fleet is more important than ever. At ELECTRIC POWER 2009, multiple presentations explored the premise that an active knowledge management strategy — requiring a blend of digital and human elements unique to each power plant — will help you extract the most productivity from your assets.

As equipment ages in fossil-fueled power plants, component wear leading to machinery failure increases as a result. Extending equipment life requires increased attention to maintenance, and one way to improve maintenance planning is to detect faults prior to failure so maintenance can be scheduled at the most cost-effective, opportune time. This type of strategy benefits from the use of additional sensors, and wireless ones can often be installed with the least time and cost.

In 1999, the Engineering Equipment and Materials Users’ Association (EEMUA) released its general guide to the design, management, and procurement of alarm systems for industrial plants. The guidance document (EEMUA 191), however, is vague about applications to specific facilities, such as electric power plants. This article specifies EEMUA 191 standards and practices applicable to the electric power industry and spells out specific variations in alarming practices that are tailored for today’s power plants.

Existing nuclear power plants are increasingly facing the conversion to digital instrumentation and controls technology. Meanwhile, new nuclear designs have digital technology integrated throughout the plant. Digital controls will soon be inevitable, so how do we make the transition as smooth as possible? Without losing focus on the technical solutions, organizations have to pay attention to the nontechnical issues as well.

It’s a digital world, and even aging power plants are experiencing the benefits of digital controls technologies. The following cover stories provide insight into the latest options and inspiration for your own plant controls projects.

In order to operate aging nuclear power plant instrumentation and control systems for up to 60 more years or longer, there must be a smooth transition from existing analog technologies to advanced digital platforms. For this to occur, electromagnetic compatibility concerns related to both qualification testing and the electromagnetic environment must be addressed to ensure safe and reliable operation of these systems within the plant’s electromagnetic and radio frequency interference environment. By understanding the regulatory requirements and sharing implementation experience, digital system upgrades can be installed successfully.

Digital fieldbus technologies, including Foundation fieldbus and Profibus, are increasingly being used with success in the nuclear and fossil fuel power industries. This article compares a conventional control system with a Foundation fieldbus – based digital control system used in a typical circulating water system in a nuclear power plant. As shown in this example, using digital fieldbus technologies can result in significant savings in terms of installation and hardware costs.

Improper pressure-sensing line design or installation is often found to be the cause of poor sensing system accuracy and response time. Here’s how to identify and solve those pesky pressure sensor problems in short order.

The debate over the benefits of using digital bus networks as the communications backbone of new power plants is all but settled. The technology is maturing, and the reliability of digital hardware is superior to that of hardwired systems. Newmont Gold Mining’s 200-MW TS Power Plant is perhaps the power industry’s best example of how a plantwide digital controls architecture can provide exceptional reliability and be significantly less costly to install.