Download Targeted LTE Solutions for Siemens Generators

Solutions for an aging fleet
Generator Upgrades and Modernization
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
GENERATOR UPGRADES AND MODERNIZATION
Presented by
Michal Gawron
Marketing Engineer
Generator Major Services Department
Siemens AG, Mülheim / Ruhr, Germany
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 2
AGENDA
Introduction into generator
maintenance and upgrades
Targeted LTE solutions for
Siemens generators
Air-cooled replacement
generator (Footprint™)
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 3
Introduction Into Generator Maintenance and Upgrades
Actual Influence of Renewable Energies (e.g. Electricity Production in Germany in 2014)
Winter Winds in Calendar Week 51
Sun and Winds in Spring at Calendar Week 11
Source: Fraunhofer-Institut für Solare Energiesysteme ISE Freiburg , 07.01.2015
• Peaks and valleys in output from renewable generation are compensated for by load variation in conventional
power plants
• More load variation means increased MVAR cycling, more starts/stops, prolonged stand-by
• Longevity of generator components is affected.
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 4
Introduction Into Generator Maintenance and Upgrades
Changing duty cycles
Example: 32 Gas-Fired Power Plant Units
Service Factor (Operating hours / Period hours)
§ New built units running in intermediate and peak load condition ( )
§ Higher stresses in most generator components, e.g. windings
§ Faster aging and wear à Improved design and maintenance concepts are required
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 5
Introduction Into Generator Maintenance and Upgrades
Typical Sources of Failures
STATOR
ROTOR
Other
9%
Slip ring
7%
Exciter
3%
Ground Short
8%
Winding
Distortion
11%
Winding
Cracks
8%
Retaining
Rings
8%
Source: VGB data base
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 6
Other
18%
Insulation
39%
Shorted Turn
13%
Damper winding /
Wedges
15%
AGENDA
Introduction into generator
maintenance and upgrades
Targeted LTE solutions for
Siemens generators
Air-cooled replacement
generator (Footprint™)
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 7
Targeted LTE Solutions for Siemens Generators
Summary of product improvements
J-Lead
Main
Connection
Lead
Retaining Ring Shrink Fit
Pole Cross Over
Gas Baffle
Teflon Coated Slotliners
Position in Rotor
Example of
Finding
Description of
Solution
• Laminated copper
• Improved geometry
• Modification of shrink fit on
retaining rings
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 8
• “Omega”-shaped pole cross
over
• Improved geometry
• Two piece blocks
• Non-conducting & more flex.
material
• Reduced friction
• Teflon coating of slot liners at
slot outlet
Targeted LTE Solutions for Siemens Generators
J-Lead Modification
J-Lead (or J-Strap)
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 9
§
Connects main lead via
radial bolt to the winding
pole
§
Subject to cyclic stresses
Targeted LTE Solutions for Siemens Generators
Stresses / Loading on J-Lead
Axial loading on J-lead due to
expansion of Rotor windings
• Highest loading at high VAR
loading
• Load cycling increases cyclic
stresses on J-lead
Radial loading on winding
due to centrifugal loading at
speed
• Frequent cycling of unit
increases cyclic stresses
on J-lead
• Over-speed increase
loading on J-lead
Stress concentrations due to
geometry
Material variations, assembly
variations, and operation can
affect cyclic life of J-strap
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 10
Deflection of J-Strap during standstill
and operation (exaggerated)
Laminated Top
Connected
J-Strap
Laminated
Bottom Connected
J-Strap
Targeted LTE Solutions for Siemens Generators
J-Lead Design Improvements
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 11
Targeted LTE Solutions for Siemens Generators
Retaining Ring Shrink Fit Modification
Rotor tooth-tops
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 12
§
Support the retaining ring
on the rotor body
§
Rotor teeth area
subjected to shrink fit of
retaining ring
§
Subject to cyclic stresses
Targeted LTE Solutions for Siemens Generators
Loads and Stresses on Rotor Tooth Tops
Compressive loads at
standstill from shrink fit
Axial loads
from locking
key
Tensile loads at
running speed from
slot content
centrifugal force
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 13
Stress concentration
at fillet radii and holes
Targeted LTE Solutions for Siemens Generators
Shrinkfit Modification of Rotor Tooth Tops
Remove tooth tops outboard of keyway
• Removes majority of cracking & fatigued material at crack
tip
• Transfer slot load from rotor to retaining ring
• Removes centrifugal loading on vent holes
Machine fillet enlargement inboard of keyway
• Removes shallow cracks & fatigued material
• Relieve the outboard land surface of the end wedges
Modifiy shrink fit on retaining rings
• Replace retaining rings as necessary
• Improve shrink fit characteristics
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 14
Targeted LTE Solutions for Siemens Generators
Retaining Ring Inspection
Rotor retaining rings
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 15
§
Subjected to Stress
Corrosion Cracking
(SCC)
§
Periodic inspection of
18-5 material is
necessary
§
Periodic inspection of
18-18 material may be
recommended,
depending on operating
conditions
Targeted LTE Solutions for Siemens Generators
Automated Retatining Ring Inspection
In-Situ
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 16
In the factory
Targeted LTE Solutions for Siemens Generators
Slot Liner Upgrade
Rotor slot liner
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 17
§
Slot liner wears off due to
thermal cycles
§
Slot liner wears off during
turning gear operation
§
Insulation between rotor
coils and rotor body
compromised
Targeted LTE Solutions for Siemens Generators
Reliability issue: Slot cell abrasion
Signs of abrasion at slot channel insulation and slot cells at end of rotor body
Abrasion rate is correlated to:
• Deflection of the rotor (D² x L4 / I)
• Time of turning-gear operation (HT)
• Speed of turning-gear operation (NT)
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 18
AGENDA
Introduction into generator
maintenance and upgrades
Targeted LTE solutions for
Siemens generators
Air-cooled replacement
generator (Footprint™)
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 19
Air Cooled Replacement Generator
Typical auxiliary systems in a generator with Hydrogen / Water cooling
• Hydrogen gas system
Provides cooling medium (H2) inside the generator
• Seal oil system
Keeps the hydrogen gas inside stator frame
• Gas inertization system
Required for de-gassing generator during stand-stills
• Stator winding cooling water system (> 200MW)
Provides cooling medium (Water) for direct cooling of
stator winding
With the FootprintTM Generator these auxiliary systems are not required and can be eliminated
saving life cycle costs
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 20
Air Cooled Replacement Generator
Typical age related problems in auxiliary systems
Corrosion
Leaking Components
Porous Seal
Lost Tagging
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 21
Wear and Tear
Vibration
Air Cooled Replacement Generator
Overview of design features
The radially direct cooled stator core provides maximum
heat transfer capability for the stator winding with minimum
flow resistance for the overall cooling circuit.
The use of different cooling zones in the active
part of the generator yields a more uniform
temperature profile.
Cooler cover with 4x25% drop in vertical
coolers, site installed for easy shipment of the
core generator and easy maintenance
.
The assembled winding is using the proven
MICALASTIC® insulation system with global
vacuum-pressure impregnation technology
providing maximum electrical endurance.
Improved enclosure design makes these
air-cooled turbogenerators suitable for
outdoor installation, allows sound pressure
levels down to 85db(A) and provides easy
access to all relevant components
Mechanically decoupled stator end
winding system with maximum rigidity to
withstand transient system faults and
maximum flexibility for thermal expansion.
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 22
The maintenance-free stator core is flexibly mounted to the outer casing
with flex plates. This prevents vibrations at double rotational frequency from
impacting the outer casing and thus the foundation tabletop.
Air Cooled Replacement Generator
FootprintTM Approach
Adaptation of base frame
• Customized base frame fits existing foundation
dimensions / No foundation mods requried
• Generator can be installed more quickly
Adaptation of stator core and rotor shaft
• Stator winding insulation with global vacuum
pressure impregnation (GVPI)
• Rotor shaft and coupling are adapted
• Plug-in or pedestal bearings
• Rotor-dynamic calculation of shaft train
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 23
Air Cooled Replacement Generator
FootprintTM Approach
Adaptation of excitation
• Excitation can be static or brushless
• Reduced operating costs with new exciter
Adaptation of bushings
• Downward
• To the side
• Or upward through the cover
Adaptation options for cooling
• Location and configuration of the cooler can be
varied
• Typically use Totally Enclosed Water to Air Cooling
• Water demand no greater than for existing
Hydrogen coolers
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 24
Air Cooled Replacement Generator
Customer benefits
Elimination of auxiliary systems
• Increased safety by eliminating hydrogen
• Reducing operation complexity and cost
Built-to-function design
• Cyclic operation modes
• Peaking mode operation
• Multiple start/stop cycles
Highest Reliability/ Availability
• Over 98% availability
• Standard spare parts only, i.e. always stocked
• Major inspection intervals can be spread over 12 years
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 25
Air Cooled Replacement Generator
Case study – South Africa
Unit
Existing Units
Replacement FootPrintTM Generator
Manufacturer
AEG (1964)
Siemens
Reactive Power [MVA]
139
139
Active Power [MW]
125,1
125,1
Power Factor
0,9
0,9
Rated Voltage [kV]
10,5
12,5
Primary Cooling Medium
H2
Air
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 26
CONTACT PAGE
Michal Gawron
Marketing Engineer
Generator Major Services
Europe, Africa, Asia-Pacific
Phone: +49 (208) 456 8134
Fax:
+49 (208) 456 8137
Mobile: +49 (173) 317 6546
E-mail: [email protected]
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 27
BACK-UP
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 28
Air Cooled Replacement Generator
Micalastic® experience base
§
The Micalastic® is used in Siemens generators for more than 50 years.
§
In addition Siemens introduced the Global Vacuum Pressure Impregnation (GVPI) Technology in
1988.
§
Since then Siemens has manufactured more than 1000 generators (air-, hydrogen- and
hydrogen/water cooled) using GVPI technology in conjunction with the Micalastic insulation system
with voltage levels up to 22 kV and rating up to 550 MVA.
§
Operational experience of these units without any stator insulation based failures since the beginnings
in 1988 demonstrates the superior quality of GVPI technology.
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 29
Targeted LTE Solutions for Siemens Generators
Product Bulletin – New J-Lead
Summary
The two J-Leads which connect the radial leads to the rotor
winding can suffer fatigue- induced cracking.
In order to avoid any forced outages and potential consequential
damage resulting from such cracking, Siemens has developed
improved J-Lead assemblies as part of its ongoing product
development process and in order to increase reliability.
Siemens recommends that the old type of J-Lead be replaced
with these improved J-Lead assemblies.
Please ask your Siemens representative or check on our service
customer portal if this product bulletin applies to a generator you
have in operation.
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 30
Targeted LTE Solutions for Siemens Generators
Product Bulletin – Short Ring Modification
Summary
The rotor tooth tops underneath the retaining rings are subject to
cracking. In order to prevent the initiation of cracks and to reduce
the impact of any existing cracks a “short ring modification” has
been developed by Siemens and it is recommended that this
measure be implemented in order to increase reliability.
This modification also encompasses machining of the shrink fit of
the retaining ring, the rotor tooth tops and the retaining ring itself.
In order to perform this modification it is necessary to remove
both retaining rings and remove the rotor from the stator.
Please ask your Siemens representative or check on our service
customer portal if this product bulletin applies to a generator you
have in operation.
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 31
Targeted LTE Solutions for Siemens Generators
Product Bulletin – Inspection Recommendation for Retaining Rings
Summary
A periodic inspection of 18Mn-18Cr1 retaining rings and a qualified NonDestructive Examination (NDE) procedure are recommended on all
generator rotors. This inspection is intended to evaluate the structural
integrity of non-magnetic retaining rings and zone rings. Siemens may
recommend replacement of retaining rings in cases of inspection findings or
exceptional operating conditions.
Cases that might be considered “exceptional conditions” include:
• Stress corrosion cracking due to chemical conditions that should not be
the normal operating environment of large electrical generators. These
include long-term exposure to saturated sodium chloride solution and
exposure to bromine under electrical fault conditions.
• Grid interaction with the generator (such as disturbances from electric arc
furnaces), which can result in rotor torsional oscillations.
• Loss-of-control events, such as out-of phase synchronization, sudden
short circuit, motorization and similar severe abnormal operation.
Please ask your Siemens representative or check on our service customer
portal if this product bulletin applies to a generator you have in operation.
Unrestricted © Siemens Osakeyhtiö 2015. All rights reserved.
Page 32