Critical parameters of hydraulic transient regimes in hydropower plants with complex water conveyance systems Jernej Mazij, Anton Bergant, Uro Karadi Litostroj Power d.o.o.Mainski Fakultet Univerzitet Crne GoreCIGRE 201511. - 14. 5. 2015, Herceg Novi, Montenegro

Contents: IntroductionTransient controlModern analysis approachCase studyConclusions and discussion

1. IntroductionTransients.. change from one steady-state to another with change of hydrodynamical and mechanical quantatiesTransients can cause damage and jeopardize the economic viabilityCauses can be forseen or unforseenInterdisplinary knowledge is neededTransient modelling using commercial softwareCase study of Doblar I HPP Moste HPP

2. Transient control - ITransients in hydropower plants in the view of impact and probability:normal,emergency,catastrophic (exceptional)The goal of transient load control:safety of the plant and personnel,identification of the most severe conditions with adequate measures,design limits.

2. Transient control - II

When to UseProtectionReliabilitySpecial DemandsProblems in RestartingFrequency of ApplicationCostHigh pressureLow pressureSurge tankHigh head, long tunnel/penstockYesYesVery goodNoneNoneVery oftenVery highAir VesselHigh head, long tunnel/penstockYesYesGoodAir compressorRoutine controlRarelyModerateInertiaAll typesYesYesExcellentNoneNoneOftenModerateRegulationAll typesYesYesGoodHigh-pressure oil installationRoutine controlVery oftenLowAir ValvesProtection of penstocksNoYesGoodFrequent maintenance and controlRoutine controlVery oftenLowAeration PipesProtection tunnel/penstockNoYesGoodNoneNoneOftenLowRupture MembraneAs a last measureYesNoGoodOutlet for water dischargeReplace membraneRarelyVery lowPRVAll typesYesNoVery goodNoneNoneOftenLow

2. Transient control - III

3. Modern analysis approachHydraulic transients are inevitable!Identify Solve Treat

SCOPE OF ANALYSISCUSTOMERSTAGE OF DEVELOPMENTTYPE OF MACHINE

4. Case study Doblar I HPP - I Storage/run-of-river development on the Soa river, Slovenia.Continuous operation since 1939, equipment by Riva Milano for 42 Hz electrical grid.Rehabilitation in period 2011 2013.Three vertical shaft 13.6 MW Francis units at Hn = 42 m.Limit of supply: turbine, spherical valves, spherical valve, generator and auxiliary equipment.Case study of sudden load-rejection.

5. Case study Doblar I HPP - II Overflow weirConnection tunnelEllipsed surge tankCylindrical surge tankDownstream surge tank NOT ON THE DRAWING!Overflow weirTwo side chambersMachine hall

5. Case study Doblar I HPP - III PROBLEMS!!

Lack of as-built documentationChange of ownership (Italy Yugoslavia)On-site geodetic surveyingRefurbishment Responsibilty of the owner to provide all the relevant documentation.

5. Case study Doblar I HPP - IV Simultaneous sudden load- rejection of three units.Simplified modelling of a complex surge tank system!Pulse burste radar level transmitter was used for surge tank water level measurements

6. Case study Moste HPP - I First HPP to begin operation on the Sava River.Continuous operation since 1952, 60 m arch gravity dam is the highest in Slovenia.Combined energy system with the potential of the Zavrnica Creek.Two vertical shaft 7.5 MW Francis units at Hn = 58 m.Limit of supply: turbine, spherical valves, butterfly valve, generator and auxiliary equipment.Case study of sudden load-rejection and closure of the butterfly valves.

6. Case study Moste HPP - II

6. Case study Moste HPP - III Simultaneous sudden load -rejection of two units.Beneficial effects of the surge tankSimultaneous closure of the inlet butterfly valves.

7. Conclusions Overwiev regarding hydraulic transients in schemes with complex water conveyance systems.Broad interdisciplinary range of konwledge is required.Two case studies of refurbishment presented, analysis performed using commercial software.Complete documentation is important in cases of refurbishment.Results of the computation agree well with the measured results.

THANK YOU FOR YOUR ATTENTION!QUESTIONS WELCOMED!

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