Impacts of running Turbines in non-design modes

Transcription

1 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: Impacts of running turbnes in non-design modes

2 Sub-Titled Chasing the Wind and the Sun 2

3 About This Presentation Anecdotal observation of changing operations Not a definitive statement on how things are Potential challenges to turbine equipment Subjective not objective 3

4 Words commonly used in this presentation generally possibly sometimes potentially depends varies often typically could if, but and maybe not definitive 4

5 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 5

6 Operating modes 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. 6

7 Reason for modes Flood control, fish passage, water quality Navigation, recreation Irrigation Economics Grid stability /variability Load demand A lot of competing stakeholders and circumstances Not definitive 7

8 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 8

9 Turbine Power History 9

10 Generator Power History 10

11 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 11

12 (recent ) Anecdotal Operation Types/Modes 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 12

13 Extremes of Operation Types/Modes (recent ) Unit 1 has 103 cycles = Ave Start / Stop cycles per year Unit 2 has 290 cycles = Ave 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 13

14 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: (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 14

15 Factor of Yield strength Design Criteria Allowable Stresses as a Factor of Yield Strength Uniform Stress Peak Stress Mean value of nominal stress Normal Operating Load Cases Exceptional Load Cases Extreme Load Cases 15

16 3 Cases Observed Changing Operation Types/Modes 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 16

17 Case 1 Francis Runner Cavitation 17

18 Case 2 Francis Runner blade crown fatigue crack 18

19 Presión Absoluta/Hu Case 3 CFD Pressure Pulsations Pulsación de Presión Ensayo U3 - CFD Tiempo (Seg) CDF SPA U3 19

20 Case 3 Kaplan Runner discharge ring fatigue 20

21 Typical Francis Turbine Power Unit 21

22 Typical Kaplan Turbine Power Unit 22

23 Static Stress and Deflection Analysis Static Stress and Deflection Analysis Modal Analysis 23

24 Modal Analysis Natural Frequencies MODE FREQUENCY IN WATER (Hz)

25 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 25

26 Thanks for your attention Voith Hydro Services 26