State of the Art Steam Turbine Automation for Optimum Transient Operation Performance

2007 ◽  
Author(s):  
Rainer Quinkertz ◽  
Edwin Gobrecht
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Operation Performance ◽  
Control Functions ◽  
Steam Power Plants ◽  
Start Up ◽  
Full Speed ◽  
Startup Performance

The growing share of renewable energies in the power industry coupled with increased deregulation has led to the need for additional operating flexibility of steam turbine units in both Combined Cycle and Steam Power Plants. Siemens steam turbine engineering and controls presently have several solutions to address various operating requirements: - Use of an automatic step program to perform startups allows operating comfort and repeatability. - 3 start-up modes give the operator the flexibility to start quickly to meet demand or slowly to conserve turbine life. - Several options for lifetime management are available. These options range from a basic counter of equivalent operating hours to a detailed fatigue calculation. - Restarting capabilities have been improved to allow a faster response following a trip or shutdown. - In addition to control of speed, load and pressure, special control functions provide alternative work split modes during transient conditions. - Optimum steam temperatures are calculated by the steam turbine control system to achieve optimum startup performance. - Siemens steam turbines are also capable of load rejection to house load, some even to operation at full speed, no load. Several plants are already equipped with these solutions and have provided data showing they are operating with shorter start-up times and improved load rejection capabilities. Finally Siemens of course continues to pursue future development.

Coordinated Control of Gas and Steam Turbines for Efficient Fast Start-Up of Combined Cycle Power Plants

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Yasuhiro Yoshida ◽  
Kazunori Yamanaka ◽  
Atsushi Yamashita ◽  
Norihiro Iyanaga ◽  
Takuya Yoshida
Keyword(s):  
Thermal Stress ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Thermal Stresses ◽  
Control Method ◽  
Coordinated Control ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Start Up

In the fast start-up for combined cycle power plants (CCPP), the thermal stresses of the steam turbine rotor are generally controlled by the steam temperatures or flow rates by using gas turbines (GTs), steam turbines, and desuperheaters to avoid exceeding the thermal stress limits. However, this thermal stress sensitivity to steam temperatures and flow rates depends on the start-up sequence due to the relatively large time constants of the heat transfer response in the plant components. In this paper, a coordinated control method of gas turbines and steam turbine is proposed for thermal stress control, which takes into account the large time constants of the heat transfer response. The start-up processes are simulated in order to assess the effect of the coordinated control method. The simulation results of the plant start-ups after several different cool-down times show that the thermal stresses are stably controlled without exceeding the limits. In addition, the steam turbine start-up times are reduced by 22–28% compared with those of the cases where only steam turbine control is applied.

Repowering and Retrofitting

2002 ◽  
Author(s):  
Andreas Pickard
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Free Market ◽  
Leading Edge ◽  
Project Planning ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Planning Stage ◽  
Reheat Steam ◽  
Plant Optimization

At the start of this new century, environmental regulations and free-market economics are becoming the key drivers for the electricity generating industry. Advances in Gas Turbine (GT) technology, allied with integration and refinement of Heat Recovery Steam Generators (HRSG) and Steam Turbine (ST) plant, have made Combined Cycle installations the most efficient of the new power station types. This potential can also be realized, to equal effect, by adding GT’s and HRSG’s to existing conventional steam power plants in a so-called ‘repowering’ process. This paper presents the economical and environmental considerations of retrofitting the steam turbine within repowering schemes. Changing the thermal cycle parameters of the plant, for example by deletion of the feed heating steambleeds or by modified live and reheat steam conditions to suit the combined cycle process, can result in off-design operation of the existing steam turbine. Retrofitting the steam turbine to match the combined cycle unit can significantly increase the overall cycle efficiency compared to repowering without the ST upgrade. The paper illustrates that repowering, including ST retrofitting, when considered as a whole at the project planning stage, has the potential for greater gain by allowing proper plant optimization. Much of the repowering in the past has been carried out without due regard to the benefits of re-matching the steam turbine. Retrospective ST upgrade of such cases can still give benefit to the plant owner, especially when it is realized that most repowering to date has retained an unmodified steam turbine (that first went into operation some decades before). The old equipment will have suffered deterioration due to aging and the steam path will be to an archaic design of poor efficiency. Retrofitting older generation plant with modern leading-edge steam-path technology has the potential for realizing those substantial advances made over the last 20 to 30 years. Some examples, given in the paper, of successfully retrofitted steam turbines applied in repowered plants will show, by specific solution, the optimization of the economics and benefit to the environment of the converted plant as a whole.

Optimizing Lifetime Consumption and Increasing Flexibility Using Enhanced Lifetime Assessment Methods With Automated Stress Calculation From Long-Term Operation Data

2013 ◽  
Author(s):  
Jan Vogt ◽  
Thomas Schaaf ◽  
Klaus Helbig
Keyword(s):  
Power Plants ◽  
Low Cycle Fatigue ◽  
Combined Cycle ◽  
Transient Temperature ◽  
Steam Turbines ◽  
Transfer Coefficients ◽  
Term Operation ◽  
Flexible Mode ◽  
Start Up ◽  
Safety Margins

In the past most of the steam turbines were designed as base load machines. Due to new market requirements based on the effect of renewable energies, power plant operators are forced to operate with more frequent start-up events and load changes, resulting in a fundamental higher low cycle fatigue (LCF) lifetime consumption. Traditional methods of lifetime assessment often use representative start-ups, for the calculation of LCF damage, which can provide very conservative results with reasonable safety margins. For a high number of starts these safety margins may result in an overestimation of the LCF damage. At Alstom, an enhanced method for lifetime assessment has been developed, that evaluates the actual lifetime consumption from real operation data in an automated manner and provides much more realistic results. The operation data is used to calculate the transient temperature distribution and heat transfer coefficients along the rotor for each start-stop cycle. The corresponding stress distribution in the rotor is evaluated by means of a Finite-Element-method analysis. Finally the number of remaining cycles is extracted for the most critical locations using material data. In combination with the creep damage the lifetime consumption is evaluated. The entire process is highly automated, but also facilitates easy monitoring through the lifetime engineer by graphic presentation of calculation results. Using this enhanced method of lifetime assessment, the computed lifetime consumption is closer to the actual value, supporting the planning of overhauls and component replacements and minimizing the risk of failure or forced outages. The utilization of remaining lifetime can be optimized in favour of a more flexible mode of operation (e.g. low load operation and fast start-up) or extension of operational lifetime for conventional and combined cycle power plants.

Repowering Considerations for Converting Existing Power Plants to Combined Cycle Power Plants

2002 ◽  
Author(s):  
Anup Singh ◽  
Don Kopecky
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Current Status ◽  
Entire System ◽  
Steam Turbines ◽  
Good Shape ◽  
The Usa ◽  
Overall Performance ◽  
Cost Studies

Most of the recent combined cycle plants have been designed and constructed as Greenfield Plants. These new plants have been designed mostly as Merchant Plants, owned and operated by Independent Power Producers. There is about 260,000 MW of conventional coal-fired and gas-fired capacity in the USA that is more than 30 years old. About 30,000 MW of conventional gas-fired capacity exists in the area of The Electric Reliability Council of Texas (ERCOT) with relatively poor heat rates in comparison to modern combined cycle plants. These plants are good candidates for HRSG repowering. In addition, there are several coal-fired units in the 200 MW range with steam turbines in relatively good shape or in a condition that can be refurbished and used in repowering. The installed cost of repowered (also called Brownfield) capacity is about 20%–40% less than for comparable Greenfield capacity. There are also other advantages to repowering. Since the site is already existing, it is easier to get the various environmental and construction permits. The efficiency of the repowered units will be significantly higher than the existing units in their current status thus increasing the overall performance of the entire system. The paper will discuss various considerations required for repowering, including steam turbine refurbishment, demolition/relocation of existing equipment, recent cost studies, and various considerations for equipment such as HRSGs.

Steam Turbine Hot Standby: Electrical Pre-Heating Solution

2019 ◽  
Author(s):  
Y. Kostenko ◽  
D. Veltmann ◽  
S. Hecker
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Steam Turbine ◽  
Power Plants ◽  
Heating System ◽  
Heating Process ◽  
Steam Turbines ◽  
Start Up ◽  
New Apparatus ◽  
General Aspects

Abstract Growing renewable energy generation share causes more irregular and more flexible operational regimes of conventional power plants than in the past. It leads to long periods without dispatch for several days or even weeks. As a consequence, the required pre-heating of the steam turbine leads to an extended power plant start-up time [1]. The current steam turbine Hot Standby Mode (HSM) contributes to a more flexible steam turbine operation and is a part of the Flex-Power Services™ portfolio [2]. HSM prevents the turbine components from cooling via heat supply using an electrical Trace Heating System (THS) after shutdowns [3]. The aim of the HSM is to enable faster start-up time after moderate standstills. HSM functionality can be extended to include the pre-heating option after longer standstills. This paper investigates pre-heating of the steam turbine with an electrical THS. At the beginning, it covers general aspects of flexible fossil power plant operation and point out the advantages of HSM. Afterwards the technology of the trace heating system and its application on steam turbines will be explained. In the next step the transient pre-heating process is analyzed and optimized using FEA, CFD and analytic calculations including validation considerations. Therefor a heat transfer correlation for flexible transient operation of the HSM was developed. A typical large steam turbine with an output of up to 300MW was investigated. Finally the results are summarized and an outlook is given. The results of heat transfer and conduction between and within turbine components are used to enable fast start-ups after long standstills or even outages with the benefit of minimal energy consumption. The solution is available for new apparatus as well as for the modernization of existing installations.

Rotor-Blade Interaction During Blade Resonance Drive-Through

2021 ◽  
Author(s):  
Roland Grein ◽  
Ulrich Ehehalt ◽  
Christian Siewert ◽  
Norbert Kill
Keyword(s):  
Power Plants ◽  
Renewable Energy Sources ◽  
Cyclic Fatigue ◽  
Combined Cycle ◽  
Plant Design ◽  
Steam Turbines ◽  
Rotating Speed ◽  
Start Up ◽  
Blade Vibrations ◽  
Fast Start

Abstract In the future energy landscape, combined cycle power plants will increasingly take the role of providing balancing power for fluctuating renewable energy sources due to their high availability and fast start-up times. This implies more frequent cycling, a larger number of speed cycles and thus new challenges for plant design and operation. One of these challenges is a potential increase of cyclic fatigue incurred by last-stage blades during start-up and coast-down. Blade vibrations might be induced by synchronous shaft vibrations when the blade resonance is excited by lateral shaft vibrations. In this paper, we report measurement results of shaft and blade vibrations observed at some Siemens Energy steam turbines. Apart from the expected increase of blade vibrations when the double rotating speed crosses the blade resonance, a distinctive dip of shaft vibrations at the low-pressure turbine bearings is observed. We argue that this phenomenon is likely related to the aforementioned interaction between blade and shaft vibrations and present a theoretical framework to describe this interaction and the observed effect.

Thermal Modeling of a Solar Steam Turbine With a Focus on Start-Up Time Reduction

2011 ◽  
Author(s):  
James Spelling ◽  
Markus Jo¨cker ◽  
Andrew Martin
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Thermal Power ◽  
The Body ◽  
Average Error ◽  
Steam Turbines ◽  
Effective Measure ◽  
Start Up ◽  
Turbine Casing ◽  
Main Steam

Steam turbines in solar thermal power plants experience a much greater number of starts than those operating in base-load plants. In order to preserve the lifetime of the turbine whilst still allowing fast starts, it is of great interest to find ways to maintain the turbine temperature during idle periods. A dynamic model of a solar steam turbine has been elaborated, simulating both the heat conduction within the body and the heat exchange with the gland steam, main steam and the environment, allowing prediction of the temperatures within the turbine during off-design operation and standby. The model has been validated against 96h of measured data from the Andasol 1 power plant, giving an average error of 1.2% for key temperature measurements. The validated model was then used to evaluate a number of modifications that can be made to maintain the turbine temperature during idle periods. Heat blankets were shown to be the most effective measure for keeping the turbine casing warm, whereas increasing the gland steam temperature was most effective in maintaining the temperature of the rotor. By applying a combination of these measures the dispatchability of the turbine can be improved significantly: electrical output can be increased by up to 9.5% after a long cool-down and up to 9.8% after a short cool-down.

Improvement in the Rapid Startup Performance for the Solar Steam Turbine

2018 ◽  
Author(s):  
Peng Wang ◽  
Gang Chen ◽  
WenFu Li
Keyword(s):  
Steam Turbine ◽  
Cyclic Fatigue ◽  
Steam Turbines ◽  
Load Variations ◽  
Start Up ◽  
Reheat Steam ◽  
Startup Performance ◽  
Transient Thermal ◽  
Life Consumption ◽  
Operation Flexibility

In the latest several years, concentrated solar plants (CSP) have been rapidly developed. Steam turbines employed in these plants are subjected to daily start up and continuous load variations. There is a general increase in demand for operation flexibility and rapid start up capability for solar steam turbines. Accordingly, how to decrease the low cyclic fatigue life consumption during the daily start up process is a hot researched topic at present, and this greatly depends on the transient thermal stress. A number of studies show that the startup schemes and the unit’s structural form decide the LCF life consumption directly. In this paper, a 50MW double cylinder (HP and ILP Section) reheat solar steam turbine is studied, and it is operated continuously with inlet steam conditions of 540[°C], 140[bar], reheat steam conditions of 540[°C], 24[bar] and exhaust conditions of 41.5[°C], 0.08[bar]. A number of comparisons are made with the FEM numerical simulation, and some optimal designs which are applied to improve the rapid start up performance and decrease the LCF life consumption during the startup are presented.

Investigation of Steam Turbine Warm-Keeping by Use of Air

2019 ◽  
Author(s):  
Dennis Toebben ◽  
Piotr Luczynski ◽  
Manfred Wirsum ◽  
Wolfgang F. D. Mohr ◽  
Klaus Helbig
Keyword(s):  
Heat Transfer ◽  
Steam Turbine ◽  
Power Plants ◽  
Calculation Model ◽  
Heat Radiation ◽  
Technical Solution ◽  
Fe Model ◽  
Steam Turbines ◽  
Data Set ◽  
Start Up

Abstract The changing energy landscape leads to a rising demand of more flexible power generation. A system for steam turbines warm-keeping provides the ability to shutdown conventional power plants during periods with a high share of renewable power. Simultaneously, these power plants are ready for grid stabilization on demand without an excessive consumption of lifetime during the start-up. One technical solution to keep a steam turbine warm is the use of hot air which is passed through the turbine. In addition, the air supply prevents corrosion during standstill and also enables the pre-warming after maintenance or long outages. This paper investigates the warm-keeping process of an intermediate pressure steam turbine (double shell configuration) through the use of dynamic numerical Finite-Elements (FE) simulations. As a representative test-case, warm-keeping calculations during a weekend shutdown (60h) are conducted to investigate the temperatures, their distribution and gradients within the rotor and the casing. For this purpose an improved numerical calculation model is developed. This detailed 3D FE model (including blades and vanes) uses heat transfer correlations conceived for warm-keeping with low air mass flows in gear mode operation. These analytical correlations take heat radiation, convection and contact heat transfer at the blade roots into account. The thermal boundary conditions at the outer walls of rotor and casing are determined by use of experimental natural cool-down data. The calculation model is finally compared and verified with this data set. The results offer valuable information about the thermal condition of the steam turbine for a subsequent start-up procedure. The warm-keeping operation with air is able to preserve hot start conditions for any time period. Most of the heat is transferred close to the steam inlet of the turbine, which is caused by similar flow directions of air and steam. Thus, temperatures in the last stages and in the casing stay well below material limits. This allows higher temperatures at the first blade groove of the turbine, which are highly loaded during a turbine startup and thus crucial to the lifetime.

Effect of Inlet Steam Temperature on the HP Section Efficiency of a Steam Turbine

2015 ◽  
Author(s):  
Yiping Fu ◽  
Thomas Winterberger
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Pressure Ratio ◽  
Control Valve ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Steam Temperature ◽  
Load Range ◽  
Lp Turbine ◽  
The Relationship

Steam turbines for modern fossil and combined cycle power plants typically utilize a reheat cycle with High Pressure (HP), Intermediate Pressure (IP), and Low Pressure (LP) turbine sections. For an HP turbine section operating entirely in the superheat region, section efficiency can be calculated based on pressure and temperature measurements at the inlet and exhaust. For this case HP section efficiency is normally assumed to be a constant value over a load range if inlet control valve position and section pressure ratio remain constant. It has been observed that changes in inlet steam temperature impact HP section efficiency. K.C. Cotton stated that ‘the effect of throttle temperature on HP turbine efficiency is significant’ in his book ‘Evaluating and Improving Steam Turbine Performance’ (2nd Edition, 1998). The information and conclusions provided by K.C. Cotton are based on test results for large fossil units calculated with 1967 ASME steam tables. Since the time of Mr. Cotton’s observations, turbine configurations have evolved, more accurate 1997 ASME steam tables have been released, and our ability to quickly analyze large quantities of data has greatly increased. This paper studies the relationship between inlet steam temperature and HP section efficiency based on both 1967 and 1997 ASME steam tables and recent test data, which is analyzed computationally to reveal patterns and trends. With the efficiencies of various inlet pressure class HP section turbines being calculated with both 1967 and 1997 ASME steam tables, a comparison reveals different characteristics in the relationship between inlet steam temperature and HP section efficiency. Recommendations are made on how the results may be used to improve accuracy when testing and trending HP section performance.

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