Online Flowrate Monitoring Experiences at Hydro-Québec

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Prosper Briggs
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1 Online Flowrate Monitoring Experiences at Hydro-Québec Jonathan Nicolle & Gilles Proulx June th conference of the International Group on Hydraulic Efficiency Measurements Trondheim, Norway

2 Summary > Intro > Results with a 200 MW Francis > Results with a 110 MW Propeller > Details of the experimental setup > Conclusions 2 Groupe Technologie, Hydro-Québec

3 Intro > Hydro-Québec the largest hydro-utility in the world Government owned Operates 350 hydro turbines in 60 plants Located in Québec, Canada mostly Francis turbines, high flowrate + medium head > Dedicated division for flow and efficiency measurement (ESP) > Research center (Ireq) Electricity production, transport and distribution CFD expertise 3 Groupe Technologie, Hydro-Québec

4 Intro > Research project: dream of online monitoring system No such thing as too much flow measurements Information is the key Accurate, affordable, usable for various types of unit > Allow for better business decisions at various levels Daily production decision (which unit, which plant should I use?) How do I operate when the head changes? Reservoir management, river spate, how do I avoid spillway? When should I clean the trash rack? What kind of losses are introduced by that manifold/ collector? Is a cavitation repair justified based on efficiency losses? Does aeration, adjacent groups, tail water level, etc, have an impact??? 4 Groupe Technologie, Hydro-Québec

Intro > For existing powerhouse flow monitoring, index seems like the best (only) choice > Q? Why is it so difficult to use index testing with low head plants?

5 Intro > For existing powerhouse flow monitoring, index seems like the best (only) choice > Q? Why is it so difficult to use index testing with low head plants? > 2 problems from CFD investigation Signal amplitude problem: sensitivity to adjacent group operation Flow homology problem: the flow distribution change with the opening of the guide vane (streamlines are not the same so should not use an index) > WK coefficients are not constants 5 Groupe Technologie, Hydro-Québec

6 Intro > Our solution: angular index First presented at 8th IGHEM conference in India Pressure behind the guide vane Measure of the guide vane angle Experimental calibration from a curve Q K( opening)* P 0.5 Coefficient WK p1-p3 WK p2-p3 Psup - p1 Pinf - p1 Psup - pinf R 2 = R 2 = Opening angle best one Q is predicted for a given angle and P combination 6 Groupe Technologie, Hydro-Québec

7 Results for a 200 MW Francis > Long penstock > 8 paths acoustic time travel (ATT) flowmeter as a reference > Index Upstream: probes at the spiral casing inlet Downstream: 4 probes behind the guide vane 7 Groupe Technologie, Hydro-Québec

8 Results for a 200 MW Francis > Calibration curve smooth Kop = Q ref / P nd order polynomial fit was enough 8 Groupe Technologie, Hydro-Québec

9 Results for a 200 MW Francis > 10 days of monitoring > Good news: 2 independant signals almost identical Normalised Normalised flowrate flowrate Angular Index Sonic Angular Index Sonic Groupe Technologie, Hydro-Québec Days Days

10 Results for a 200 MW Francis > A surprise After some time, a constant offset ( 1.2%) was detected between the relative and the reference method Automatic correction of the ATT method Angular index unaffected and lower dispersion 120 Flow ± 1 m 3 /s 120 Flow ± 0.5 m 3 /s Normalised flowrate RMS 0.5 % Sonic series 1 Sonic series 2 Normalised flowrate RMS 0.2 % angular index Opening [deg] 10 Groupe Technologie, Hydro-Québec Opening [deg]

11 Results for a 110 MW propeller > 4 pressure probes located between the guide vane and the runner. External WK for high pressure. > Semi-spiral casing > Again smooth calibration curve based on previous current meters measurements Propeller index quadratic P K coefficient Groupe Technologie, Hydro-Québec Angle [deg]

12 Results for a 110 MW propeller > Able to follow head change Index results taken close to the expected head Measurements are from a similar group (normalized) 1.1 angular index 25.5 m Current meters 25.5 angular index 27.5 m Current meters 27.5m Angular index 30 m Current meters 30 m 1.05 Qnorm 1 Flow ± 1 m 3 /s RMS % Opening [mm] 12 Groupe Technologie, Hydro-Québec

adjustments) and 2 standard automatic procedures

13 Results for a 110 MW propeller > Online monitoring: a real story Comparison between «optimal» (manual adjustments) and 2 standard automatic procedures Interface showing last 3 hours 13 Groupe Technologie, Hydro-Québec

Experimental setup > Pressure probes Must be able able to take

manifold 4 probes are enough for Francis, ok for propeller Two

> Guide vane Angular encoder is preferred to servomotor

14 Experimental setup > Pressure probes Must be able able to take the full head when the guide vanes are closed Averaged with a manifold 4 probes are enough for Francis, ok for propeller Two words: Automatic Bleed. > Guide vane Angular encoder is preferred to servomotor strokes before after > Signal acquisition Filter when the guide vanes move 14 Groupe Technologie, Hydro-Québec

15 Conclusion > Until now, not much attention has been given to online monitoring Pursue different goals than absolute measurements (complementary) More interesting & difficult for low head plants Demonstrated angular index usefulness for 2 very different turbines (random error %) Captured phenomena that would be difficult to observe otherwise ATT flowmeter recalibration Automatic PFR procedures impact on efficiency What s next > Building a new experimental set More industrial Fully numerical signal Bleed valves controller > Starting to integrate flow data to the various HQ systems 15 Groupe Technologie, Hydro-Québec

16 If you think angular index is a good system, try it or contact us!!! 16 Groupe Technologie, Hydro-Québec

17 Good questions you might ask Why use an angular encoder instead of servomotor stroke? What happened with the ATT flowmeter on the Francis? What about CFD and experimental comparisons? Is the calibration transposable from one group to another? What if the turbine is replaced? What are the pitfalls for angular index? 17 Groupe Technologie, Hydro-Québec

18 Why prefer angular encoder > Servomotor strokes would work in theory > but as a CFD guy, I ve been struggling with servomotors stokes for my whole life Old powerhouse, modifications, extensions, not always on plan In-house system not enough accurate Pre-loading different for each unit Zero definition not always the same Servomotor is of value to the operator > Angular encoder is fresh start Accurate & return a value that has a meaning in terms of fluid flow Angular position is of value to the fluid flow analyst 18 Groupe Technologie, Hydro-Québec RETURN

19 ATT reference flowmeter > Not exactly sure Acquired the data and analysed them afterward > Seems like there was a problem with one of the path and the system recalibrated itself > Dont know if the flow value was good before or after the event > Important point is the random error or RMS value of both methods 19 Groupe Technologie, Hydro-Québec RETURN

20 CFD vs experiment > Not exactly there but not far either > Propeller Mean error 1.1% > Francis Mean error 0.9% CFD exp K coefficient K Coefficient Opening Angle CFD 14 exp Opening Angle RETURN 20 Groupe Technologie, Hydro-Québec

21 Calibration generality > Question still open for debate > Is the calibration applicable to a similar unit? K would probably be very close but may be not identical > Is a new calibration curve necessary when the turbine change? Limited results from a kaplan turbine seem to suggest so Variation in the meridionnal flow distribution affects the index 21 Groupe Technologie, Hydro-Québec RETURN

22 Pitfalls > Be as accurate as you can for the guide vane opening, it is quite sensible > Calibration might not be valid for the whole operating range > If you use a low number (< 4) of downstream probes, you might have unwanted sensitivity > Bleed valves are essentials to survive de-watering of the unit and long term operation > It not just a change in technology, it requires a change in mentality, so plan data integration ahead. Flow values are of no use if they do not make their way through the compagny operating systems. Beware of admistrative inertia 22 Groupe Technologie, Hydro-Québec RETURN

Flowrate Measurement Background

A Report of Acoustic Transit Time Accuracy Field Work Performed In North America By James T. Walsh Director Accusonic Technologies Flowrate Measurement Background The use of multiple path acoustic transit