Russia Power 2006 14-16 March 2006 Moscow, Russia · Russia Power 2006 14-16 March 2006 Moscow, Russia ID Number: 61 Power Diagnostics® Service for steam turbines and generators

Russia Power 2006 14-16 March 2006 Moscow, Russia ID Number: 61

Power Diagnostics® Service for

steam turbines and

generators

Vanessa Bauch

and

Michael Killich

Siemens Power Generation

Germany

1/20 © Siemens AG 2006. All rights reserved.


Abstract Due to market conditions we see a growing demand of flexibility in operating and

maintaining power plants. Power plants which were designed for base load operations have to

cycle and this has an enormous effect on the availability and reliability of the power plant and

the turbo-generator in particular. To keep the risk calculable it is of outmost importance to

know the condition of the machines. Another aspect is the necessity of flexibility due to price

changes on the electricity markets. During high price periods nobody wants to shut down for

a planned overhaul and it might by reasonable to use all the engineering reserves of the

machine and to operate it beyond its nominal design limits for some time.

These goals can only be reached when the condition of the power plant and its major

components can be assessed during normal operation using online diagnostics systems. But

online diagnostics does not mean a fully automated software solution, because a real

diagnostic can only be achieved using all the engineering capabilities and recourses in the

back offices of the turbo-generator manufacturers.

Another very important issue is the availability and the avoidance of forced outages using

such diagnostics. Used as a watch dog, diagnostics can help to make the business more safe

and predictable.

Siemens Power Diagnostics® therefore is designed as a remote expert centre where we offer

engineering support on a long term contractual basis. A software solution which is capable of

learning the normal behaviour of the plant prevents the engineers from dealing with trivial

occurrences. Using this software and the and the engineering knowledge, it is also possible to

decide that a turbo-generator running out of its normal operation limits concerning vibration

for example can be operated until the next planned outage evaluating the risk.



Introduction

Liberalization/deregulation of the electricity market continues to expand in many parts of the

world. This requires that power producer owners and operators deliver electricity more

efficiently and at competitive pricing. In parallel with these market demands, the operation of

the complete power plant – turbine, generator, boiler and auxiliaries – must improve

reliability, availability and utilization/efficiency.

But even in parts of the world not experiencing liberalization/deregulation the growing

demand in some regions for electricity is pushing power producers towards these same

improvements. Whatever the market environment, this is poses a special challenge for more

mature units, including base-load units that have to cycle and for plants that have not been

maintained for optimal performance.

To achieve these demands cost reduction and technical innovation programs were

implemented in power generation process. Furthermore, a higher flexibility in operating and

maintaining the plants is necessary according to the actual market conditions. Older base-load

units have to cycle, which creates higher stress on the materials. Planned overhauls are

postponed to avoid uneconomic standstill time. Uprating of power output of existing units to

the absolute design limits is often used as an additional option to tap maximum profit during

peak price periods. In parallel with all these market demands, operation of the complete

power plant with the steam turbine set and generator as key components must be enhanced

through higher reliability, availability and utilization.

The traditional way of handling maintenance business is not aligned to these market

requirements. One way to achieve the objective of flexible and short-term outage planning is

to use innovative technologies combined with close cooperation with the OEM.

There are a variety of solutions to help meet critical customer needs. Siemens Power

Generation is in the forefront of providing numerous solutions: proven modernization

designs, advanced inspection systems, new maintenance and repair services, and more. A

very powerful Siemens tool to improve plant availability is Siemens Power Diagnostics®. The

system features a modular structure focused on technical function groups of the power plant.

It works in combination with the conventional I&C system as an additional diagnostic tool

for early detection of condition changes or fault indication and for preventing unexpected

malfunctions. The use of comprehensive on-line data acquisition, internet data transmission

systems, task-related data analysis, and an expert background knowledge base at the Remote

Power Diagnostics® Centers enable detailed diagnosis of the actual plant condition.



With human expert support and engineering solutions from the manufacturer, together with

the knowledge-based supervisory diagnostic system, long term condition-based plant

operation with enhanced reliability and profitability will be possible. This Power Diagnostic®

Service enterprise encourages the client to

make inspection decisions on turbo set components on a condition- and risk-based

maintenance strategy,

implement better life-time management under technical and commercial aspects,

practice smoother turbo set operation for avoiding frequent overstressing of the

machine, resulting in life extension.

Condition monitoring with the Power Diagnostic® Service leads to effective live cycle asset

management.

Power Diagnostics®

Siemens Power Generation is offering Power Diagnostics® Services for steam power plants.

Today Siemens provides these services globally for more than 200 OEM installations for gas

turbines. The expertise on gas units is being applied to the entire steam plant island.

References

Equipment monitored by Power Diagnostics®

182

129

9 111

020406080

100120140160180200

Gas Turbine

Generator(Gas Turbine)

Steam Turbine

Generator (Steam Turbine)

Balance of Plant

Num

bero

f Uni

ts

94 sites212

156

94

11

Figure 1: References



Power Diagnostics® is a comprehensive service with modular components designed to

monitor, analyze and diagnose the complete turbine island. This advanced service product is

a highly sophisticated remote diagnostic system. It combines global engineering experience,

sophisticated monitoring, data processing, trending, analysis tools, and security systems.

Different Parts work hand in hand and form the backbone of Power Diagnostics® Services

(see figure 2). Together they enable detailed diagnostics of the plant condition and support

development and implementation of condition-based maintenance strategies and the

optimization of the plant operations.

Power Diagnostics® Services performing analysis and diagnostics:

Using extensive OEM unit knowledge

Using advanced diagnostic tools/techniques

Providing trend analysis and problem identification

Providing root-cause analysis done by expert teams

Key elements of Power Diagnostics® Services

OEM engineering expertise

OEM engineering expertiseComprehensive online data acquisition

Online data acquisition

Data processing / analysis

Data processing / analysis

Use of an expert knowledge network

Expert knowledge network

Figure 2: Key Elements of Power Diagnostics® Services



On-line, real-time operating data acquired from customer locations are transmitted to the

Power Diagnostics® Centers. Data is acquired from sensors attached to customers’ turbines,

generators or auxiliaries. These are supported by PCs and the I&C system.

The infrastructure for the data handling process and the “intelligent” software is provided

from one of the Siemens Power Diagnostics® Centers (Mülheim, Erlangen and Orlando)

supplying the data acquisition, management and event-driven data storage. Data is

transmitted to the center and processed through a series of advanced modules and artificial

intelligence software to make sure that measured values do not exceed thresholds and

operating condition limits, and that the machine and/ or systems are running in a normal

mode with a predictable behavior.

Skilled Siemens engineers and specialists in various functions, such as thermodynamics, rotor

dynamics, fluid mechanics, processes and construction from Siemens departments in Orlando

and Mülheim are connected with the Power Diagnostics® Centers (see figure 3).

This engineering knowledge, combined with the use of advanced diagnostic tools and

techniques enable trending and analysis to address a broad range of operating needs that are

specific to each customer. The objective is early detection of abnormal operating conditions,

assessment by Siemens engineers and specialists and timely recommendations to customers.

Any necessary operating adjustments can be made or other actions taken to continue

successful performance and avoid unplanned downtime.

To summarize, the Power Diagnostics® Center performs analyses and diagnostics using

highly sophisticated learning software modules, provides trend analyses, problem

identification, and root-cause analyses conducted by human experts. The learning software

solution helps the experts to avoid spending their time and resources on minor issues. Also,

since the pool of information is coming from a large fleet, the experience base grows much

faster than it would from only a single plant. Even if no abnormal condition is detected in the

turbine-generator our engineering experts are able to generate recommendations on plant

operation and/or maintenance actions. These recommendations are designed to maximize the

equipment’s performance, reliability and availability and potentially extend outage intervals.



©Siemens Power Generation 2004. All Rights Reserved14-16 March 2006

Power Generation 5Bauch Vanessa, O263

Russia Power

Power Diagnostics®

- Infrastructure for data handling

Online real-time operating data transmission

Wor

ldw

ide

netw

ork

for

data

exc

hang

e

Your Power Plant

Use of advanced diagnostic tools and techniques for:

Monitoring of machine conditions

Data collection / processing

Analysis of limit values and deviation from normal behavior

Power Diagnostics® Center

MonitoringAnalysis

Online DiagnosisOffline Diagnosis

Online Diagnosis

Engineering Know-how:

Interpretation and diagnosis

Data assessment

Development of recommen-dations for future operations,repairs and/or modernization

Expert Network Team

Reports

Access

Info

Figure 3: Data handling

There are close to 20 separate diagnostic modules in the Power Diagnostics® product line – In

introducing these services for operating steam turbine-generators, the following diagnostic

products are already available, with others to follow:

Shaft and bearing vibration

Monitoring of turbine generator vibration behavior by measuring shaft and bearing

vibration and operating variables over extended period.

End winding vibration

One of the turbine generator components that is subjected to the most stress are the

generator end windings. Despite the precision design and production that goes into

these items, the vibration behavior of the end winding nevertheless changes over the

course of operation as a result of ageing and thermal influences. Changes in vibration

behavior can occur as a result of disturbances in the grid, switching operations and

lightning strikes. An analysis of the condition of the end windings can be made by

acquiring these vibration (oscillation) levels.



Torsional Vibration

Electrical disturbances in the grid, switching operations and lightning strikes can

cause torsional vibration in power plant turbine generators, resulting in the line of

shafting being subjected to elevated, sometimes impermissible loading. This is why

measurement and evaluation of such events and processes is so important; this also

contributes to correct assessment of the condition of the turbine generator with respect

to condition-based maintenance.

All three types of vibrations can be handled on one hardware and software platform

VIBROCAM 5000 RF monitoring: Digital radio frequency measurement system, permits early detection

and indication of incipient damage. It is based on the detection of partial discharge

that results in short-circuiting across part of the insulation.

Krawal: A tool developed for plant design and engineering of the thermodynamic

processes integrated into online diagnostics to compare current process data with

anticipated values.

Figure 3: Steam Turbine Generator Product Portfolio

Currently 5 modules help collect the dataBasis for diagnostic works:

Bearing and Shaft Vibration MeasurementEnables vibration behavior assessment of a turbine island

End Winding Vibration MonitoringMeasures vibration levels at stator end windings to determine changes occurring within the generator

Torsional Vibration MonitorMonitors vibration levels due to torsional excitation which can cause blade and / or rotor failures

Process engineering Tool (KRAWAL)Thermodynamic module, which helps compare current process data with expected values

Radio Frequency Measurement System (SIEMON)Monitors generators and high voltage equipment by partial discharge measurement

Figure 4: Overview of available service modules



Contract

The concept of Power Diagnostics® is designed to fit in Siemens Strategic Alliances

Programs (see figure 5). These long-term service contracts are designed to develop the

business from transactional and price-driven models to performance-driven contracts with

value-based pricing. Performance-driven, value-based pricing denotes mutually agreed

objectives such as availability, reliability or other customer benefits, measured and evaluated

in a Score Card. The prices for services ordered within such long-term contracts are therefore

fixed prices from a list of specifications plus a bonus / penalty based on the results of the

Score Cards.

The result is an integrated solution for deregulated markets where Siemens is more or less

responsible for all maintenance issues within the turbine island, i.e. the risk sharing level, the

level of goal alignment and the value-based pricing.

The idea of a value-based pricing and risk sharing is a key element in an Long Term Program

contract. One possibility to achieve this is by implementing Score Cards, developed and

mutually agreed upon during the negotiation process by the contract partners.

This concept of a value-based pricing system is available for Power Diagnostics® Service

Contract also. In this case the customer’s benefits have to be identified and fixed in a

mutually agreed matrix. These benefits can be in the form of events such as avoidance of a

forced outage or early detection of an imminent failure. Early detection, for example, gives

the customer additional time for planning and can therefore shorten the outage duration.

Mut

ual B

enef

it Project ManagedMaintenance Contract

TMS

TFA

OPSA

LTP

O&M

TransactionalTransactional ExpandedScope / RiskExpanded

Scope / RiskPerformance

DrivenPerformance

Driven

MC

Alliances

Technical Field Assistance

Operating PlantService

Agreement

Total Maintenance Services

Long TermProgram

Operations &MaintenanceDiagnostic

compatible data collection: proactive

Today:• Fire fighting• Reactive

Minimum of continous costs

Figure 5: Overview Strategic Alliance Programs



Customer Benefits

Increasing cost pressure in power generation forces power plant operators to optimize service

and maintenance and to maintain or even improve reliability and availability . This objective

can be reached by applying a condition-based maintenance strategy. Siemens Power

Diagnostics is a powerful tool to support the power plant operator in achieving this objective

But only with the combination of on- and off-line measurements / monitoring can a high

degree of assessment quality be attained.

The goal of Power Diagnostics® Services is to help identify, assess and diagnose plant

operating abnormalities that could result in inefficiency and forced outages. Also, the

system's condition monitoring capabilities offer more effective life cycle asset management,

which is especially important for flexible operation of base-load units.

For plant operators, the provision of advance detection of abnormal operating conditions and,

ultimately, follow-up actions can result in optimized operation, higher availability and

improved turbine island efficiency. For the original equipment manufacturer, information

collected through Power Diagnostics® can be used to further improve products and services,

including improvements in hardware service life and durability, to mitigate collateral

equipment damage through early detection, to enhance reliability, and to improve scheduling

and optimize the duration of maintenance outages.

Results from Power Diagnostics® can contribute to development of recommendations for

future operations, repairs and/or modernization of customer’s equipment.

This Power Diagnostics® Service encourages the customer to:

Make inspection decisions on turbo set components in terms of a condition- and risk-

based maintenance strategy

Improve life-time management through improved data and data analysis

Improve turbo set operation to avoid frequent overstressing for potential life

extension.

The bottom line is this: Siemens Power Diagnostics® Services can help identify a problem

before it impacts operation, allowing plant personnel to make necessary adjustments for

continued operation. In some cases Power Diagnostics® can help turn an unplanned shutdown

into a scheduled outage with all the personnel and materials needed to help make optimal use

of the customer’s time and money (see figure 6 and case study).



t

Shut down

Identifiable Trend Early detection of an unplanned stand still by diagnostic experts.

Preparation for the

stand still

Stand still

Start-up

Delta t Economized time in fact of

early problem detection and change from an unplanned to

a planned stand still.

Limit Value Signal progression

Superiorlimit value

Figure 6: Benefit of an early damage detection

For the short term Power Diagnostics® provides the power plant operator with regular

documentation of the monitored components on a high quality data basis. In case of recurring

problems and/or detected operation abnormalities/trends etc., exclusive access to the

engineering network with guaranteed capacities is provided. A Power Diagnostics® customer

is treated as a preferred customer. Based on continuous monitoring and comparison with the

historical data, early detection of problems and damages can be realized. This helps the

power plant operator to save costs and to increase sales. But it also offers the possibility to

continue plant operation with justifiable risks, for example in phases with high prices on the

electricity market.

For the long term Power Diagnostics® forms the basis for

Condition-based maintenance

Flexible operation

Life-time extension

Maintaining optimum efficiency

Availability enhancement



can provide …

Regular documentation of machine conditions

Access to the Siemens Expert Network

Early detection of many operating issues

Information for proactive decision making

Condition-based maintenance

Flexible operation

Efficiency/ Availability/ Reliability Improvement

Risk sharing, extended warranties

Performance related payment

Cost savings

are the basisfor …

in combination with long term service contracts …

Power Diagnostics® services …

Summary and Outlook

Figure 7: Customer Benefits on short term and long term view



Case study

Online diagnostics does not mean relying exclusively on software solutions. It is the

combination of skilled OEM personnel, the operation experience of an entire fleet and the

application of advanced diagnostic tools that make for success.

The basis for successful diagnostic work is formed by the high quality data pool, combined

with a powerful hardware and software system for data processing and an expert team for

data assessment. The interaction of an advanced monitoring/ analysis system and experts

leads to an established statement about machine behavior, as well as to an observation of

problem causes and recommendation for the elimination of the problem.

Requirements for a vibration analysis and monitoring system:

Diagnosis-oriented data acquisition

Diagnosis-oriented data analysis and data reduction to meaningful key

parameters with a minimum loss of information

Diagnosis-oriented data processing for off-line diagnostics by experts

Automatic determining of the machine-model-specific and measuring-point-specific

normal conditions and behavior of the key parameters within the excursion for normal

operating parameters

Diagnosis-oriented monitoring – automatic evaluation of key parameters as compared

to the values for normal conditions and behavior, with data archiving in the event of

deviation from normal conditions.

All of these requirements are fulfilled by the Vibrocam5000 hardware and software systems.

The following example illustrates the procedure to take in the event that vibration problems

arise. Power Diagnostics® has demonstrated its abilities already several times as in the

following case:

4 weeks ahead of a planned outage in a turbine-generator set all measured vibration values

are in normal range, but variations in the generator rotor data were detected. An additional

measurement was carried out and the resulting data were analyzed and assessed by the

Siemens Power Diagnostics® Expert Team. The result of the measurement was the detection

of a crack in the axial water guidance in the protection sleeves of the generator rotor. It was

recommended to exchange the complete rotor in order to get the power plant back in

operation.

Through early detection and planning work the rotor was exchanged at the scheduled outage

using a pool rotor: Chances of finding the crack during the scheduled outage were very low,



since the scope did not include the generator. Power Diagnostics® Services were significant

in preventing a forced outage.

The turbine-generator set has one high pressure and two low pressure turbines and a water

cooled generator. The turbine and generator side at the low pressure turbine, the turbine and

exciter side at the generator, the exciter bearing and the shaft pump were examined by

vibration test points (see figure 8).

System configuration

Absolute bearing vibrations (mm/s)

Relative shaft vibrations (µm)

Figure 8: System configuration and vibration test points

Examination of the vibration behavior between 10th February – 10th March showed changes

in the vibration behavior as from 21. February (see figure 9). The measurement values were

still under the limit values so the operator was not really alarmed. Concerning vibration

issues changes are always indications, even if limit values were not exceeded therefore the

situation was seen as a task force issue.

In order to get a detailed view of the vibrations the summarized values of the amplitudes as

well as the vibration vectors were examined. The vibration vectors showed high changes of

the vibration level - about three times higher. The high variations of the vibration level

indicate a generator vibration problem (see figure 10).



Change of vibration behavior

as from 21.02.05

Vibration behaviorbetween 10th February – 10th March 2005

Figure 9: Vibration behavior between 10th February and 10th March

Comparison 2th February and 30th March 2005

2th February = dark blue

30th March = light blue

stable

Extended changesExciter Bearing Shaft Pump

LP2 Bearing –Turbine side

LP2 Bearing –Generator side

Generator Bearing –Turbine side

Generator Bearing –Exciter side

Figure 10: Comparison 2nd February and 30th March



Experts gather from the significant changes of the vibration levels based on the know-how

from development & design and the experience an exciter current depending issue. On this

account a correlation vibration behavior versus excitation current was realized. Following

distinctive features could be determined

No linear correlation between exciter current and vibration level

Increased vibrations at higher and lower excitation current

Lowest vibration level at 6,8 kA excitation current

(see figure 11)

LowestVibration level at 6,8 kA

excitation currentIncreased vibrations at higher and lower excitation current

Vibration behaviorversus excitation current

Figure 11: Vibration behavior versus excitation current

Based on this results following statements were made:

The typical vibration behavior with regard to the exciter current influence has been

changed since 21. February

There has to be an additional influencing parameter which has a high dependency on

the exciter current and causes the vibration

One possible reason for this behavior could be the influence of the primary cooling water

temperature on the vibration behavior. An additional test was realized to analyze the behavior

of the vibration by changing cooling water temperature under constant excitation current.

The result of the test showed that the machine had an identical behavior (see figure 12).



Comparison: changes due to reactive power <> changes due to primary water temperature

Changes of the reactive power Changes of the primary water temperature

>> the reaction of the machine is identical

Figure 12: Comparison: changes due to reactive power versus changes due to primary water temperature

Based on the generator design a crack in the axial water guidance was assumed (see figure

13).

During the standstill a crack in the axial water guidance in the protection sleeves of the

generator rotor was detected. About 1,8 liters of water were located in the air gap between

water guidance and rotor. The complete rotor was exchanged in order to get the power plant

back in operation.

The crack was located on one cooling water pipe. Due to the water in the air gaps a better

heat transfer could take place which leads to a thermal unbalance within the rotor. Only when

the rotor and the cooling water temperature were on the same level there was no heat flow

and so far no vibrations. This happened at about 6,8 KA (the point of the lowest vibration

level)



Old generator shaft design – CoolingSpare rotor / water guidance (Protective pipe)

weld

welds

2120mm

water chamberR a d i a l pipe

Axial water guidance

12mm

relative movement due to shaft bending

Compensator

3mm

cam direction by protection pipe

weld

welds

2120mm

water chamberR a d i a l pipe

Axial water guidance

12mm

relative movement due to shaft bending

Compensator

3mm

cam direction by protection pipe

Figure 13: Old generator shaft design – Cooling spare roter/ water guidance (protective pipe)

On the sketch in figure 6 you can see the generator cooling design.

The rotor is equipped with 4 cooling water pipes (2 water supplies, 2 drain pipes)

The cooling pipes are fixed with welded cams.

The relative movement due to shaft bending leads can lead to cracks in the weld of the

pipe

Based on the above mentioned case study two main points can be pointed out:

Continuous monitoring is important to ensure early detection of operation issues in

this way time and money can be saved.

The know-how from development and design as well as the know-how and

experience of specialists are necessary to solve problems in a fast and responsive way.



Summary

Due to the changing market conditions all over the world, the traditional way of dealing with

maintenance business no longer fits in with these new environmental requirements. The

solution is to achieve a flexible and short-term outage planning process and a reduction of

costs. Diagnostics, in particular in combination with Strategic Alliances, can fulfill all these

demands, as they are tailor made solutions.

Monitoring and diagnostics is a rapidly evolving field in power generation. The combination

of available IT technology and on-line expertise provides cost-efficient service and benefits

to the customer.

In summary:

Increasingly more specific analysis and diagnostic technology is now available

To maximize the benefits for power plants, the challenge is to employ all requisite

technologies via a single platform

Global networking of a running fleet enables OEM experts to analyze data quickly and

respond rapidly to customer requirements

On-line diagnostics - in combination with remote expert knowledge - is the key to

condition-based maintenance and provides cost-efficient service for reliable plant

operation.

For the customer, it is important in any given situation to have access through a diagnostic

platform to the knowledge of the people who designed his equipment. For the equipment

supplier, the greatest benefit is to have live feedback from his own "running technical

systems" that enables him to optimize his own learning process.

And last but not least, on-line diagnostics paves the way from scheduled maintenance to

condition-based maintenance, thus helping customers operate their units at maximum

profitability.



Literature [1] Taud R.; Scheidel M.: Use and Experience with Gas Turbine On-Line Diagnostics, Power Gen

Europe, Barcelona 2004 [2] Bender, K.; Grühn, M.; Rukes, B.; Scheidel, M.: Online Remote Diagnosis of Turbosets and

Combined Cycle Power Plants; VDI-Bericht Nr.: 1641, VDI-Verlag, Düsseldorf, 2001

[3] Adam, G.; Bode, A.: Ferndiagnose und Teleservicesystem für GUD-Kraftwerke; VDI-Bericht Nr.: 1566, VDI-Verlag, Düsseldorf, 2000

[4] Brummel, H.-G.; Scheidel, M.; Thompson, E.: Gut behütet aus der Ferne; Siemens Power Journal, Heft 1/00

[5] Ulbrich, A; Gobrecht E.; Siegel M. R.; Brückner J.: High Steam Turbine Operating Flexibility Coupled with Service Interval Optimization, Power Gen Europe, Barcelona 2004


Documents

Russia Power 2006 14-16 March 2006 Moscow, Russia · Russia Power 2006 14-16 March 2006 Moscow, Russia ID Number: 61 Power Diagnostics® Service for steam turbines and generators