impacts of running turbines in non-design modes impacts of running turbines in non-design modes...

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Impacts of running Turbines

in non-design modes

Author: Mr. Steven R. Potter, Western Regional Manager/

Welding Engineer/CWI

Voith Hydro Services Inc., 2885 Olympic Street, Springfield,

OR 98478, USA. Tel: 541-743-6353

Email: [email protected]

Impacts of running turbnes in non-design modes – 2016

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Sub-Titled

Chasing the Wind

and

the Sun

Impacts of running turbines in non-design modes – 2016

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About This Presentation

• Anecdotal observation of changing operations

• Not a definitive statement on how things are

• Potential challenges to turbine equipment

• Subjective not objective


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Words commonly used in this presentation

generally

possibly

sometimes

potentially

depends

varies

often

typically

could

if, but and maybe

not definitive


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In This Presentation

• Type/Modes of unit operation

• Operating modes / Reasons for

• Original design intent

• Design vintage

• Effects of varying operation on turbines

• Potential impacts on equipment

• Conclusions


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• Hydropower plants (typically) operate as base, intermediate,

load following or peaking power plants.

• Have (generally) the ability to start within minutes, in some

cases seconds.

• Plant operation depends heavily on its water supply.

• Many plants do not have enough water to operate at capacity

on a continuous basis.

• Plants may change their operating mode depending on the

time of year.


Operating modes

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• Flood control, fish passage, water quality

• Navigation, recreation

• Irrigation

• Economics

• Grid stability /variability

• Load demand

• A lot of competing stakeholders and circumstances

• Not definitive


Reason for modes

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Design Intent

• Hydro Turbine designs are (often) unique

• Designed around site and circumstances

• Head and flow determine turbine type and operating mode

capabilities

• Economics of site

• Materials and manufacturing era

• Design period tools

• Determination of best operating condition


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Turbine Power History


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Generator Power History


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Design Vintage

• (generally)

• Design Vintage determines the sophistication of the

engineering

• Older designs are (often) more conservative and empirical

• Newer designs use powerful computer analytics and modeling

• Older designs use heavier manufacturing gauge and cruder

alloys

• Newer designs (often) use closer tolerances

• Older are more unknown quality, newer less design margin

Presentation name | place or presenter | YYYY-MM-DD

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Anecdotal Operation Types/Modes

(recent email)

“As of 2007 to present Unit 1 has 103 cycles and Unit 2 has

290 cycles. We follow a set hourly schedule. Worse case, we

change generator loading once per hour.”

Stated at the 2016 NWHA conference

“We are looking at power markets of 5 minute increments”

Stated at the 2016 CEATI conference

“Units are operating at 110% of nameplate rating”


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Extremes of Operation Types/Modes

(recent email)

• Unit 1 has 103 cycles = Ave. 11.5 Start / Stop cycles per year

• Unit 2 has 290 cycles = Ave. 32.2 Start / Stop cycles per year

• Why are we interested in Start / Stop cycles?

• Barring Load Rejection / runaway conditions, Starts and Stops

represent the largest stresses on a machine

• Highest torque, heat loads, temperature rise, surface wear, potential

for systems failure

• More stops and starts and or constant adjustment = less life cycle

• Running very low or very high output (maybe) outside the design

intent


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Typical Design Criteria

Load spectrum: (assumed load spectrum to achieve safety factor)

1.) rated operation = 105,9 rpm (+ 55% extra load for magnetic pull)

No. of starts: 17 940 (23 start/stop per month for 65 years)

2.) load rejection = 148,2 rpm (assumed ~140% of the rated speed)

No. of events: 500 (assumed)

3.) runaway = 212 rpm (max. over speed acc. to generator data)

No. of events: 5 (assumed)

• (If) Unit 1 operates at 11.5 cycles annually it (could) (maybe) have

a life cycle of 1565 years, (but) probably not

• Don’t assume this criteria applies to every machine


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Design Criteria

Allowable Stresses as a Factor of Yield Strength

0.5

0.6

0.75

0.65

0.78

0.98

0.4

0.48

0.6

0

0.2

0.4

0.6

0.8

1

1.2

Normal Operating Load

Cases

Exceptional Load Cases Extreme Load Cases

Facto

r o

f Y

ield

str

en

gth

Uniform Stress

Peak Stress

Mean value of

nominal stress


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Observed Changing Operation Types/Modes

3 Cases

1. Francis units vintage 1960’s 50mW; being remotely

operated by owners power marketing group, operated to

sell on the power spot market, adjustments every ten

minutes or less, gate variance 20-55%. Original design

anticipated base / intermediate loads

2. Francis units re-runnered in 2000’s 38mW; operated as a

slave to upstream units, low output, running in or near

rough zone

3. Kaplan units vintage 1990’s 155mW; operated to fine tune

water passage, created draft tube pulses


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Case 1 Francis Runner Cavitation


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Case 2 Francis Runner blade crown fatigue crack


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-0.5

-0.3

-0.1

0.1

0.3

0.5

0.7

0.9

1.1

1.3

1.5

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80

Pre

sió

n A

bso

luta

/Hu

Tiempo (Seg)

Pulsación de PresiónEnsayo U3 - CFD

CDF SPA U3

Case 3 CFD Pressure Pulsations


20Impacts of running turbines in non-design modes – 2016

Case 3 Kaplan Runner discharge ring fatigue

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Typical Francis Turbine Power Unit


22Impacts of running turbines in non-design modes – 2016

Typical Kaplan Turbine Power Unit

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Static Stress and Deflection Analysis

Static Stress and Deflection Analysis Modal Analysis


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Modal Analysis – Natural Frequencies

MODEFREQUENCY IN

WATER (Hz)

1 90.05

2 205.53

3 256.11

4 325.22

5 331.82

6 366.18


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Conclusions

• Hydro operations are changing due to external conditions

• Intermittent renewables are driving changes

• Most of the fleet was not designed to for new applications

• Probably expect that life cycle will be reduced

• May see increased maintenance demands

• Reduced reliability and production

• Increased costs of operation

• Refurbishments need to consider future use plans


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Thanks for your attention

Voith Hydro Services


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