Combined Cycle Plant Performance Monitoring

Author(s):  
Michael McClintock ◽  
Kenneth L. Cramblitt

Monitoring thermal performance in the current generation of combined cycle power plants is frequently a challenge. The “lean” plant staff and organizational structure of the companies that own and operate these plants frequently does not allow the engineering resources to develop and maintain an effective program to monitor thermal performance. Additionally, in many combined cycle plants the highest priority is responding to market demands rather than maintaining peak efficiency. Finally, in many cases the plants are not designed with performance monitoring in mind, thus making it difficult to accurately measure commonly used indices of performance. This paper describes the performance monitoring program being established at a new combined cycle plant that is typical of many combined cycle plants built in the last five years. The plant is equipped with GE 7FA gas turbines and a GE reheat steam turbine. The program was implemented using a set of easy-to-use spreadsheets for the major plant components. The data for the calculation of indices of performance for the various components comes from the plant DCS system and the PI system (supplied by OSIsoft). In addition to the development of spreadsheets, testing procedures were developed to ensure consistent test results and plant personnel were trained to understand, use and maintain the spreadsheets and the information they produce.

Author(s):  
F L Carvalho ◽  
F H D Conradie ◽  
H Kuerten ◽  
F J McDyer

The paper examines the variability of key parameters in the operation of ten thermal power plants in various commercial grid environments with a view to assessing the viability of ‘on-demand’ plant performance monitoring for heat rate declaration. The plants of various types are limited to coal- and oil-fired units in the capacity range of 305–690 MW generated output. The paper illustrates the influence of control system configuration on effective and flexible power plant management. The analysis of variability indicates that there is a reasonable probability of achieving adequately stable operating periods within the normal operating envelope of grid dispatch instructions when thermal performance monitoring and display can be undertaken with a high confidence level. The levels of variability in fuel quality, which were measured during nominally constant levels of fuel input and generated output, range from about +1 per cent for oil-fired plants to about ±5 per cent for coal-fired power plants. The implications of adopting on-line monitoring of unit heat rate as an input to the generation ordering and unit commitment process are potentially significant cost and energy conservation benefits for utilities having a high proportion of coal- and oil-fired generation.


Author(s):  
Helmer Andersen

Fuel is by far the largest expenditure for energy production for most power plants. New tools for on-line performance monitoring have been developed for reducing fuel consumption while at the same time optimizing operational performance. This paper highlights a case study where an online performance-monitoring tool was employed to continually evaluate plant performance at the Kalaeloa Combined Cycle Power Plant. Justification for investment in performance monitoring tools is presented. Additionally the influence of various loss parameters on the cycle performance is analyzed with examples. Thus, demonstrating the potential savings achieved by identifying and correcting the losses typically occurring from deficiencies in high impact component performance.


Author(s):  
Komandur S. Sunder Raj

The objectives of an effective power plant performance monitoring program are several-fold. They include: (a) assessing the overall condition of the plant through use of parameters such as output and heat rate (b) monitoring the health of individual components such as the steam generator, turbine-generator, feedwater heaters, moisture separators/reheaters (nuclear), condenser, cooling towers, pumps, etc. (c) using the results of the program to diagnose the causes for deviations in performance (d) quantifying the performance losses (e) taking timely and cost-effective corrective actions (f) using feedback techniques and incorporating lessons learned to institute preventive actions and, (g) optimizing performance. For the plant owner, the ultimate goals are improved plant availability and reliability and reduced cost of generation. The ability to succeed depends upon a number of factors such as cost, commitment, resources, performance monitoring tools, instrumentation, training, etc. Using a case study, this paper discusses diagnostic techniques that might aid power plants in improving their performance, reliability and availability. These techniques include performance parameters, supporting/refuting matrices, logic trees and decision trees for the overall plant as well as for individual components.


Author(s):  
H. Jericha ◽  
F. Neumayer

A conceptual design study for a 120 MW combined cycle plant is presented here. Values of 60% thermal efficiency are at present the realm of very large gas turbines of most advanced design with power outputs of 300 to 500 MW. For industry and district heating plants it would be of most economic value to achieve similar thermal efficiencies in medium size gas turbines and combined cycle plants as they are being installed in Central European cogeneration and district heating plants. The authors propose by concerted application of recent research results to achieve this goal for medium size combined cycle plants. Design measures incorporated are transonic turbine stages, an innovative cooling system and a 600 degree reheat steam turbine.


Author(s):  
Rolf H. Kehlhofer

In the past 15 years the combined-cycle (gas/steam turbine) power plant has come into its own in the power generation market. Today, approximately 30 000 MW of power are already installed or being built as combined-cycle units. Combined-cycle plants are therefore a proven technology, showing not only impressive thermal efficiency ratings of up to 50 percent in theory, but also proving them in practice and everyday operation (1) (2). Combined-cycle installations can be used for many purposes. They range from power plants for power generation only, to cogeneration plants for district heating or combined cycles with maximum additional firing (3). The main obstacle to further expansion of the combined cycle principle is its lack of fuel flexibility. To this day, gas turbines are still limited to gaseous or liquid fuels. This paper shows a viable way to add a cheap solid fuel, coal, to the list. The plant system in question is a 2 × 150 MW combined-cycle plant of BBC Brown Boveri with integrated coal gasification plant of British Gas/Lurgi. The main point of interest is that all the individual components of the power plant described in this paper have proven their worth commercially. It is therefore not a pilot plant but a viable commercial proposition.


Author(s):  
Ranga Nadig

Abstract Power plants operating in cyclic mode, standby mode or as back up to solar and wind generating assets are required to come on line on short notice. Simple cycle power plants employing gas turbines are being designed to come on line within 10–15 minutes. Combined cycle plants with heat recovery steam generators and steam turbines take longer to come on line. The components of a combined cycle plant, such as the HRSG, steam turbine, steam surface condenser, cooling tower, circulating water pumps and condensate pumps, are being designed to operate in unison and come on line expeditiously. Major components, such as the HRSG, steam turbine and associated steam piping, dictate how fast the combined cycle plant can come on line. The temperature ramp rates are the prime drivers that govern the startup time. Steam surface condenser and associated auxiliaries impact the startup time to a lesser extent. This paper discusses the design features that could be included in the steam surface condenser and associated auxiliaries to permit quick startup and reliable operation. Additional design features that could be implemented to withstand the demanding needs of cyclic operation are highlighted.


Author(s):  
Andrea Passarella ◽  
Gianmario L. Arnulfi

As gas turbine exhaust gases leave the turbine at high temperature, heat recovery is often carried out in a combined heat-and-power system or in the steam section of a combined-cycle plant. An interesting alternative is a mirror cycle, which involves coupling together a direct Brayton top cycle and an inverted Brayton bottom cycle; this results in significantly higher power output and efficiency, though at the expense of added complexity. The research illustrated in the present paper was based on two in-house codes and aimed to analyze different plant configurations, one of which was a heat recovery (regenerative) top cycle with the heat exchanger hot side located between the top and bottom cycle turbo-expanders. The authors call this configuration a distorting mirror, as the hot side may not be at atmospheric pressure. A parametric analysis was carried out in order to optimize plant performance vs. pressure levels. Simulation showed that, at the design point, very good performance is obtained: efficiency close to 0.50 with plant cost (per megawatt) about half vs. combined-cycle plants. An off-design analysis showed that the mirror plant is a little more sensitive to changes in load than a simple Brayton, single-shaft GT.


Author(s):  
W. Peter Sarnacki ◽  
Richard Kimball ◽  
Barbara Fleck

The integration of micro turbine engines into the engineering programs offered at Maine Maritime Academy (MMA) has created a dynamic, hands-on approach to learning the theoretical and operational characteristics of a turbojet engine. Maine Maritime Academy is a fully accredited college of Engineering, Science and International Business located on the coast of Maine and has over 850 undergraduate students. The majority of the students are enrolled in one of five majors offered at the college in the Engineering Department. MMA already utilizes gas turbines and steam plants as part of the core engineering training with fully operational turbines and steam plant laboratories. As background, this paper will overview the unique hands-on nature of the engineering programs offered at the institution with a focus of implementation of a micro gas turbine trainer into all engineering majors taught at the college. The training demonstrates the effectiveness of a working gas turbine to translate theory into practical applications and real world conditions found in the operation of a combustion turbine. This paper presents the efforts of developing a combined cycle power plant for training engineers in the operation and performance of such a plant. Combined cycle power plants are common in the power industry due to their high thermal efficiencies. As gas turbines/electric power plants become implemented into marine applications, it is expected that combined cycle plants will follow. Maine Maritime Academy has a focus on training engineers for the marine and stationary power industry. The trainer described in this paper is intended to prepare engineers in the design and operation of this type of plant, as well as serve as a research platform for operational and technical study in plant performance. This work describes efforts to combine these laboratory resources into an operating combined cycle plant. Specifically, we present efforts to integrate a commercially available, 65 kW gas turbine generator system with our existing steam plant. The paper reviews the design and analysis of the system to produce a 78 kW power plant that approaches 35% thermal efficiency. The functional operation of the plant as a trainer is presented as the plant is designed to operate with the same basic functionality and control as a larger commercial plant.


Author(s):  
Jeffrey N. Phillips ◽  
Meherwan P. Boyce ◽  
Jay Grandmont ◽  
Leonard Angello

A spreadsheet-based performance monitoring software program has been developed which uses OEM correction curves and thermodynamic analysis to compare actual simple cycle gas turbine performance to expected performance over the full-range of operation including part-load. The program has been designed to require a minimum of user set-up and can interface with widely-used, third-party data historians to access plant operating data in real-time. In addition to providing overall plant performance indicators, the program also provides component-level indicators such as combustion turbine compressor section efficiency. An overview of the algorithms used to calculate actual and expected performance is provided. The advantages and shortcomings of this approach are compared to those used by others. Results are presented from initial testing of the software on a 500 MW combined cycle power featuring two GE 7FA combustion turbines. Performance results include data on the compressor section efficiency of a 7FA over a wide range of operating conditions.


Author(s):  
Alexander V. Mirzamoghadam

Knowing the sources behind degradation of gas turbine power and heat rate and the performance of other power plant equipment are critical to equipment manufacturers for guaranteeing their respective performances over the life cycle as well as to utility/plant owners for cost reasons. Many power companies are trying to improve equipment reliability by focusing on Performance Monitoring and the application of advanced diagnostic technologies. The first part of the paper describes a method to monitor gas turbine compressor efficiency, forecast an efficiency decay rate in terms of operating hours, introduce the logic leading to an optimum schedule pertaining on-line/off-line water washing, correct measured real-time gas turbine power and heat rate with respect to the new and clean reference point, and then deduce the respective turbine and compressor power contributions to gas turbine net power degradation. An example is used to aid the planning of a rigorous but effective schedule in compressor washing. The second part focuses on assessing degradation at the plant level (simple or combined cycle). The derived gas turbine degradation methodology is integrated with the overall plant performance degradation, and as a result, the maintenance effectiveness of the most recent outage can be measured. The proposed methodology is applied to a hypothetical combined cycle plant, allowing the identification of possible sources of plant deterioration with recommendations for corrective actions to improve overall power and heat rate.


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