ALSTOM HYDRO PELTON PEL TON POWER PLANT PL ANT
POWER
ALSTOM HYDRO PELTON POWER PLANT Producing cost effective clean renewable energy has become an issue of growing importance in the current context of climate change, increasing cost of fossil fuels, and the need for individual country energy independence. Hydropower is by far the world’s leading renewable energy source because it is a mature technology and one of the most economic power sources available. In addition, it has a number of specic advantages that other renewable energy sources don’t have, such as the possibility to store large quantities of energy for several weeks or months, only releasing this energy
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when it is most needed, to meet power consumption levels during peak demand periods. Pelton hydropower plants are particularly well adapted for sites with high heads. The high energy density levels associated with these sites require a relatively low investment per MW capacity, resulting in competitively priced electricity. Furthermore, these types of power plants are characterised by fast response times and one of the widest power adjustment capabilities possible. These plants are thus an ideal solution for providing ancillary services such as primary and secondary
network regulation, spinning reserve or black start. Based on the combination of competitively priced electricity, peak power sales revenues and the supply of ancillary services, Pelton hydropower plants show very favourable economic performance levels, in open electricity market environments.
WHY CHOOSE A PELTON HYDROPOWER PLANT? MAIN FUNCTIONS • Can store large amounts of energy for weeks or months • Act as a quick response for peak load energy supply • Provide ancillary services (network frequency & voltage regulation, reserve capacity, black start capability, reactive power production) KEY ADVANTAGES • Clean, renewable power source • Relatively low cost per installed MW • High efciency over a wide range of power output • Fast output adjustment capability (very complementary to thermal power plants)
ALSTOM HYDRO – THE PLANT INTEGRATOR™ Alstom Hydro provides a complete range of Pelton hydropower plant electro-mechanical equipment. This includes turbines, generators and control systems as well as optimised hydro-mechanical and balance of plant equipment.
Turbines
Generators
Depending on the customer preference, these can be supplied either separately or as an integrated turnkey plant. In the latter case, specialised Alstom teams have developed specic skills for optimising the complete plant conguration so that the highest global water-to-wire performance is achieved.
Hydro-mechanical equipment
Control systems & BOP
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PELTON HYDROPOWER PLANT CONTROL SYSTEMS Alstom Hydro developed and qualified specific control system solutions as well as dedicated machine control equipment, in order to guarantee safe, optimised power plant operations. In 2008, Alstom Hydro launched the ALSPA® CONTROPLANT™ Series 7 control system, a major evolution for Alstom Hydro control systems. The turbine speed load governor (NEYRPIC® T.SLG) and the automatic voltage regulator (CONTROGEN™ AVR), both Alstom Hydro proprietary equipment, are integrated in the ALSPA CONTROPLANT system. This new CONTROPLANT solution was designed to meet three key requirements: reliability, modularity, and openness. • Reliability of the system is aimed at meeting the highest plant availability standards. This is guaranteed through the use of industrial products from carefully selected market leaders, the use of secured communication networks and the capability
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of the system to implement redundancy at all levels. • Modularity allows to define cost effective customized solutions by using pre-qualified modules, for medium to large new or retrofit plants, in simplex or non-redundant congurations. • Openness is achieved through the use of Ethernet at all levels, supporting both a large set of international communication protocols and gateways to connect third party equipment. A complete set of dedicated plant control software is provided with the CONTROPLANT system, providing all standard control room functions, enhanced human-machine inter face (HMI) with advanced information management tools, remote access through web server, report generation, alarm management, statistics etc. Complementary CONTROCAD® engineering software tools are provided for maintenance and conguration
of ALSPA CONTROPLANT, and a plant simulator is available for personnel training. Finally, the Hydroset software package provides a complete set of advanced hydro process functions such as joint unit control, dam control and valley control optimisation. The latter is achieved through long term and short term forecasting tools.
ALSTOM HYDRO REINFORCES PELTON TECHNOLOGY Pelton turbines are particularly well suited for heads between 200 m and 1800 m. Since 1927, Alstom Hydro has supplied over 300 Pelton turbines worldwide, with power ranges between 1.2 MW and 202 MW, for heads between 120 m and 1247 m. Alstom Hydro Pelton turbines have either one or two injectors for horizontal shaft and between one and six injectors for vertical shaft congurations. Alstom Hydro produces turbines that are adapted to the needs of each pro ject and take into account customer specifications such as water head, water discharge, operating range and power generating requirements, in addition to power plant space considerations.
Pelton scale model test laboratory
After this, the complete turbine is model tested in its complete operating range in the hydraulic scale model test laboratory.
As turbine efciency is of key importance in power plants, Alstom Hydro has heavily invested to create a Global Technology Centre in Vadodara, India to make further developments in this area. The centre, which was built in 2008, includes a Pelton scale model test laboratory with one of the highest head testing capacities for Pelton turbines in the market. The most up-to-date design technology is used in both of the Alstom Hydro Global Technology Centres (Grenoble, France and Vadodara, India), to create optimised shapes for Pelton turbines. This covers all hydraulic water passage parts, such as the manifold, injectors, runner, housing and the tail water channel. Alstom engineers use the latest in-house and market computational uid dynamics (CFD) software, sophisticated 3D surface generating tools and Finite Element Method (FEM) techniques for this purpose.
Horizontal shaft Pelton test-rig
Real life power plant conditions are simulated in the laboratory in order to test how the life-size horizontal and vertical Pelton turbines will operate on site. Experimental tests are carried out using a scale model of the turbine, which includes all hydraulic parts, in order to optimise turbine efciency, overall hydraulic behaviour and the nal hydraulic design. Tests cover a variety of aspects including head, discharge, output, efficiency and runaway.
Computational uid dynamics
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WHAT IS DIFFERENT ABOUT ALSTOM HYDRO PELTON TURBINES? Alstom Hydro Pelton turbines have a number of advantages compared to Francis turbines for high heads, because they provide: • Increased exibility with a jet dispatching capability • Increased safety using deectors in case of overspeed • Easier access to the runner for maintenance and dismantling (particularly important in case of silt abrasion)
Manifold hydraulic design
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Alstom Hydro manufactures both cast and forged runners for Pelton turbines. Although more expensive, the forged version offers the best material quality. Alstom Hydro customers can benet from specic technology initiatives: • An optimised manifold design for improved jet quality and runner efciency • A specific needle design for self-
closing injectors, for improved jet quality and head loss reduction • A specic advanced jet dispatcher governing function • A specic spherical valve design for increased safety and exibility • A Hooped Pelton patented runner design that minimises fatigue stress, vibration levels and replacement cost.
A SPECIFIC ADVANCED JET DISPATCHER GOVERNING FUNCTION One of the key advantages of Pelton turbines is their broad range of power output levels. It is possible to select the number of active jets required in order to always ensure turbine operating at optimum efciency levels. In order to do this, Alstom Hydro has embedded a specific advanced jet dispatcher function in the NEYRPIC T.SLG, which continuously adapts the number of jets in operation. This advanced function is available as an option in the NEYRPIC T.SLG. Jet dispatcher e fcienc y curve
The jet dispatcher also manages the injectors opening and closing sequence, to guarantee load balance
on the turbine, in order to minimise power f luctuations and transverse
mechanical loads, during conguration transitions.
A SPECIFIC SPHERICAL VALVE DESIGN The main power plant inlet valve is a critical piece of plant equipment as it plays an important role for both the safety of individuals and the plant itself, particularly in the case of turbine nozzle closure failure. Spherical valves can fulfil these functions and are the best solution for Pelton turbines with heads over 300 m. The spherical valve’s design provides a metal-to-metal tightness eliminating head limitations. They also facilitate safe maintenance operations on downstream equipment. Alstom Hydro can provide spherical valves with diameters and working pressures adapted to customer needs. To date, the biggest diameter produced by Alstom Hydro measured 3.5 m and the maximum working pressure was 1610 mWC. Alstom Hydro prod-
uces three types of spherical valves and is one of the only manufacturers to propose valves with a monobloc welded body. The Alstom Hydro spherical valve range includes: • Valves with a monobloc welded body • Valves with a body in 2 bolted asymmetrical parts • Valves with a body in 2 bolted symmetrical parts
Spherical valve with a monobloc welded body
ADVANTAGES OF SPHERICAL VALVES WITH A MONOBLOC WELDED BODY • Light weight compact size for easier installation • No risk of water leakage between body coupling anges • Innovative design for easier bearing and seal maintenance operations, without plug extraction
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THE HOOPED PELTON RUNNER DESIGN CONCEPT Traditional Pelton runner buckets have both a hydraulic function, converting water’s kinetic energy into a force, and a mechanical function, converting this force into torque on the shaf t line. This results in cyclical forces on the bucket attachments that cause fatigue and vibrations, necessitating frequent inspection. In response to this problem, Alstom Hydro has developed and patented a Hooped Pelton runner design, capable of providing the same hydraulic efficiency levels as a standard Pelton, but better able to withstand mechanical stress. Instead of the traditional allin-one Pelton casing, the Hooped
Hooped Pelton system
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Pelton buckets are manufactured separately and attached to two hoops. The Hooped Pelton buckets have only a hydraulic function and the hoops carry out the mechanical function by transmitting the torque to the shaft line. ADVANTAGES OF HOOPED PELTON RUNNERS • Lower maintenance costs and fewer plant outages • Greatly reduced vibration levels (by up to 90%) • Reduced replacement costs • Shorter delivery time • Increased material quality levels • Higher quality silt abrasion protective coating Fatigue stress levels are reduced by replacing the individual bucket attachments with the Hooped system. This eliminates the need for repeated quality inspections and associated labour costs and plant outages. Replacement costs of ageing runners are reduced, as it is possible to
replace individual buckets instead of the complete runner. As Hooped Pelton runners are manufactured in several parts, this enables better optimisation of the supply chain and a signicant reduction in delivery time for customers. A high level of material quality is guaranteed as buckets are cut out of high quality small cast or forged stainless steel pieces. The individual buckets provide optimal conditions for the application of silt abrasion protective hard coating to all areas.
Computational uid dynamics
ALSTOM HYDRO SILT ABRASION PROTECTIVE SOLUTIONS Caused by the presence of solid silt particles in water, silt abrasion causes severe damage to turbines and plant outages in extreme cases. In Pelton turbines, silt abrasion can impact the needle tip, nozzle seal rings and runner buckets resulting in lower turbine performance and shorter turbine operating life. Alstom Hydro develops, case by case, design and coating solutions for customers to combat silt abrasion problems through: • The application of a protective layer of hard coating to components • The development of turbine designs that take into account critical erosion zones AL STOM HYDRO HIGH VEL OCITY OXY FUEL (HVOF) HARD COATING This technology is particularly well suited to Pelton runners. Coating is sprayed onto all surface areas using a robot. The high abrasion and fatigue resistance of the HVOF coating is achieved using a metal substance embedded with tungsten carbide ceramic powder. The application technique used creates a high-density layer of coating with very strong bonding capabilities, which is on average 0.3 mm thick.
Silt abrasion test-rig
SPECIFIC HYDRAULIC DESIGN INITIATIVES • Analysing the flow dynamics in order to adjust the turbine design prole in areas that are more prone to erosion • Use of numerical computational uid dynamics simulation tools to predict effects of silt abrasion on turbine performance
65 m/s and silt concentration levels up to 10 kg/m3. The results of these tests enable Alstom Hydro to evaluate the life span of existing coating solutions and to develop even better high performance solutions for customers.
LABORATORY ABRASION MEASUREMENT TECHNIQUES In 2008, Alstom Hydro installed a new high-tech silt abrasion test-rig in their Global Technology Centre in Vadodara, India.
HVOF protective coating spraying
The abrasion test-rig is designed to carry out experimental research on severe turbine silt abrasion by simulating conditions comparable to those on site. It is designed to take into account a water jet ow speed up to
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ADVANCED GENERATOR TECHNOLOGY MODERN GENERATOR DESIGN TECHNIQUES Alstom Hydro has extensive experience with all types of horizontal and vertical generators driven by Pelton turbines. Design concepts are based on the most up-to-date calculation methods, ensuring both reliable and economic operating. In reply to design requirements for high-speed units and in order to guarantee high availability and stability of the power-generating unit,
Mechanical FEM* calculation of a pole & plate
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Alstom Hydro generator main features include: • Structural design with oblique elements • Permanently pre-stressed stator core • Vacuum Pressure Impregnation insulation system (VPI) & slot ripple spring • Self ventilated rotor rim (standard or high speed design) • Self pumping bearing pads OBLIQUE ELEMENTS Oblique elements are designed to meet requirements like roundness, concentricity and stability of the generator in all operating conditions. The oblique element stator frame provides a rigid connection against eccentric displacement but allows free concentric thermal expansion. This arrangement also avoids buckling of stator laminations, which occurs in rigid frames with non-exible foundation connections. In addition, the connection to the base plates is totally maintenance-free.
PERMANENTLY PRE-STRESSED STATOR CORE The clamping bolts are positioned in the stator yoke and ensure high, constant distribution of the stator core pressing. Spring elements compensate any potential settling of the stator lamination in order to maintain the pre-stress in the stator core over long service periods. Alstom Hydro’s stator core lamination pressing system is specially designed for units with high load cycles due to frequent starts and stops. *Finite Element Method
VPI INSULATION SYSTEM The reliability of the stator winding is determined primarily by the quality of its stator winding technology. Alstom Hydro has been using the MICADUR® insulation system for more than 40 years. Additional research has led to further improvements to this system, providing excellent results on units even under severe conditions. To ensure permanent thermal and mechanical coupling between the stator bar surface and the stator core, the straight portions are supplied with «round-packing» consisting of a double-folded conductive polyester foil, filled with a curable rubber compound. This system also ensures excellent grounding after installation due to the gap-free installation.
MICADUR stator bar insulation
hoses, to the warm oil collecting ring, and then on to the external oil cooler before coming back to the cool oil collecting ring, located below the bearing.
The uniform VPI production process ensures high insulation quality of the MICADUR insulation system with the following main advantages: • Class F temperature requirements are met • High dielectric strength and voltage endurance values with low loss factors • Proven system for all units up to 30kV • Excellent corona-resistance • Highly resistant to oil, water, and other coolants • Excellent mechanical properties SELF PUMPING BEARING PADS Alstom Hydro has developed a simple and effective oil-fed bearing pad system that can be used for all types of generators. Designed with pumping gaps (pockets), the guide bearings act as pumps as soon as the machine is started. Oil travels through drains located at the end of the pumping gaps, via
the associated supervision and monitoring elements and pre-start check functions. ADVANTAGE S OF AL STOM HYDRO SELF PUMPING BEARING PADS • Failure and maintenance-free system • Increased bearing operating availability and reliability • Safe run down is ensured in case of failure of the whole auxiliary power supply • Reduced start-up time of the unit • Overspeed security
Self pumping bearing pads
The pumped oil ow increases with the speed of the moving bearing surfaces. Therefore, in case of runaway, much more oil is pumped through the system. This prevents excessive temperatures of both the oil and the bearing. This eliminates the need for external electric driven pumps and
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. m o t s l A f o s k r a m e d a r t d e r e t s i g e r e r a R U D A C I M d n a D A C O R T N O C , C I P R Y E N , A P S L A . m o t s l A f o s k r a m e d a r t e r a N E G O R T N O C d n a T N A L P O R T N O C , R O T A R G E T N I T N A L P
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