TECHNICAL NOTE

Controller testing facility on 32-5 MW water turbineD.J. Winning, B.Sc, Ph.D., A.G. Marshall, B.Sc, D.G.E. Findlay, B.Sc,

K.H. Aitken, B.Sc, and N.F. Grant, B.Sc.Indexing terms: Servomotors, Turbogenerators, Control equipment

Abstract: As part of a collaborative programme of work between university and industry on the control ofhydro-generating units supplying power to the UK national grid, equipment has been installed on a 32-5 MWunit which permits the testing of new controllers in a realistic, operational environment. A central feature ofthis equipment, which includes a new independent high-pressure servomotor, is that it permits the generatingunit to be returned quickly to operational use with its existing controller. Full integration with the powerstation operator's controls, automatic control scheme and protection, permit the controllers under test to beevaluated under normal operational conditions.

1 Introduction

Collaborative research between the University of Glasgowand the North of Scotland Hydro Electric Board on hydro-turbine governing has been in progress for some years. Theearly work was concerned with the analysis and modellingof the pipeline, tunnel and turbine systems1 and withimproved governor designs.2 More recently, a prototypeelectronic governor including an additional servomotor wasinstalled and tested3 on an operational 32 -5 MW water tur-bine. This gave much better power response to frequencydisturbances when grid-connected than the originalgovernor, while still preserving stability when supplying anisolated load.

Since then, the work has been concerned with improvingstill further the characteristics of the governors,4 and withdeveloping a turbine controller which is used not only ingoverning but also performs the sequential control oper-ations required in the run up and loading of the unit. Topermit this and future work to proceed unhindered by theneed to rebuild the entire experimental equipment in thepower station each time a new controller is designed andconstructed, a 'controller testing facility' has been installedwhich rationalises the experimental equipment and providesa tool for controller and governor testing. This paperdescribes the facility.

The operational water turbine, on which the experimen-tal equipment has been installed, is one of four 32-5 MWgenerating units at Loch Sloy Power Station, situated onthe west bank of Loch Lomond, in Scotland. The arrange-ment of this generating equipment is well documented.5

an entirely new servomotor was installed which operated onthe same shaft as the existing servomotor. By the use ofmanually operated by-pass and isolation valves and an elec-trical 'controller selector switch', changeover between, onthe one hand, the existing station governor and servo-motorand on the other, the experimental controller/governor andservomotor could be effected in a few minutes. This rapidtransition between the two sets of equipment permittedexperimental work in even short breaks in operational ser-vice. The 'controller selector switch' is used to switch anumber of alarm, trip and control signals so that only theselected governor will generate alarms or trips and respondto station control signals.

Total isolation of the experimental equipment is alsoprovided by links in the marshalling cubicle and this greatlyfacilitates preliminary development of new controllers/governors in the station environment without affecting theoperational availability of the generating unit in any way.

Cables connect the marshalling cubicle and the control-ler cubicle, in which all signals to and from the powerstation are connected to the controller/governor throughpermanently installed signal conditioning equipment. Thesignals between this conditioning equipment and thecontroller/governor are all at standard logic and operationalamplifier voltage and impedance levels and are available onplugs or sockets. Thus all controllers operate to a welldefined and unchanging interface, require no special inter-face equipment (e.g. relays or power amplifiers), and canbe rapidly installed in the station. This provides not onlythe obvious advantage of simplifying controller design, but

2 Experimental equipment

2.1 General arrangement

Fig. 1 shows the general arrangement of the experimentalequipment. It proved impracticable to position the watercontrol valve using the existing hydraulic servomotor,which was controlled by a mechanical speed governor, sinceno suitable electrical interface could be added. As a result,

Paper 1004C, first received 18th April and in revised form 15thSeptember 1980Dr. Winning, Mr. Aitken and Mr. Grant are with the Department ofElectronics and Electrical Engineering at the University of Glasgow,Glasgow G12 8QQ, Scotland. Mr. Marshall is with the North ofScotland Hydro-Electric Board, Engineering Department 16 RothesayTerrace, Edinburgh EH3 7SE, Scotland. Mr. Findlay is with YARDLtd., Charing Cross Tower, Glasgow G2 4PP, Scotland

IEEPROC, Vol. 127, Pt. C, No. 6, NOVEMBER 1980

power stationcontrol equipment

hydraulicservomotorsystem

marshalling cubicle& isolation links

controllerselector switch

station interface,signal conditioning& simulation equipment

• controllercubicle

permanentequipment

definedinterfacereplacabteequipment(governors &controllers)

Fig. 1 General arrangement of experimental equipment

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also means that initial development of controllers can beundertaken in the university laboratory, with the controllerunder test being connected to a comprehensive simulationof the power-station plant, having an identical interface tothat used on site.

2.2 Station interface

The principal items of the permanent equipment in thecontroller cubicle are shown in Fig. 2. Power-supply failureor failure of the microprocessor governor or controller aretreated like hydraulic-oil-pressure failure by the station pro-tection and result in emergency shutdown of the generator,see Section 2.3. All off/on signals are optically isolated andoutput signals are additionally taken through relays to giveclean contacts for station circuits. Commissioning of newcontrollers/governors is facilitated by switches in all chan-nels which permit isolation from and simulation of stationcircuits.

The servo controller provides closed-loop control of theservomotor to the 'desired servo position' supplied by thegovernor. 'Servo local control' permits the station 110Vbattery to be used to move the servomotor even when a.c.

supplies have failed. A frequency signal for the governor/controller is supplied by the frequency transducer whichuses digital techniques to measure the period of a phasorcombination of generator terminal voltages and currents.It thus provides a signal even under generator-fault con-ditions and is also capable of operating when generatorexcitation has failed using the voltages generated by gen-erator remanent magnetism. This cubicle also contains anumber of other facilities including buffer amplifiers whichprovide signals to external recording and data logging equip-ment. This permits monitoring of governor/controller sig-nals with out risk to the governor/controller.

2.3 Hydraulic servomotor system

Fig. 3 shows the general arrangement of the experimentalservomotor system. Valves A and B are closed and C and Eare open when an experimental governor is in service, thepositions being reversed when the station governor is in ser-vice. Hydraulic accumulators provide not only hydraulicdamping during normal operation of the oil pump but alsoenergy storage which permits safe operation (in conjunctionwith the non return valve D) of the water control valve even

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power supplyunits 5V*15V

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signals

clean

contacts In, indicators& on/off /remote switches

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frequencytransducer

frequency

(digital & analogue)

generatorvoltage& currenttransformers

AB.AC phase-phase

voltagesB,C phase current

isolatingvoltage & currenttransformers

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Fig. 2 Principal elements of station interface

Buffer amplifiers, meters for monitoring purposes and simulationfacilities are also included

358 IEEPROC, Vol. 127, Pt. Q No. 6, NOVEMBER 1980

with pump or pump a.c. supply failure. Valve G permitscompletely independent shut down of the experimentalservomotor by station protection in the event of failure ofthe experimental controller/governor. This valve operatesin the event of a drop in oil pressure or when the micro-processor or a power supply fails.

3. Conclusions

The Controller Testing Facility has been successfullyinstalled on an operational hydro-electric generating unitand has permitted tests to be carried out with novelcontrollers in a real operating environment. Work has nowprogressed to the point at which a controller is undergoingassessment under normal operational conditions with thegenerating unit supplying power to the grid. This equip-ment has also permitted tests to be performed on the Sloyhydraulic system to obtain data to build up a comprehen-sive simulation including many of the non linearities notnormally included. The techniques used in simulating theSloy unit are applicable to other plant.

The construction of the test equipment has been of con-siderable benefit to the university in providing a test bedfor ongoing work and one which has been readily availableover a period of some years. It has accustomed university

staff and post graduate students to the realities of an indus-trial environment enabling them to design controllers whichare not only throretically satisfactory but which are capableof controlling real plant. It has also stimulated the interestof the power station engineers in the work and their sugges-tions have assisted in ensuring that the controllers designedwould be satisfactory in operational service.

4 Acknowledgments

The authors would like to extend their thanks to the lateA.M. CocHran of the North of Scotland Hydro-ElectricBoard and T.R. Foord of Glasgow University with whoseencouragement and interest the work was commenced andto G.W. Bryce and to P.W. Agnew who carried out theinitial work. The financial and engineering support receivedfrom the North of Scotland Hydro-Electric Board, and thecontinuing access to operational plant are gratefullyacknowledged. Thanks are also due to the staff of Sloy/Awe Generation Group, in particular to I. Phillipson andA.L. Grant. Prof. J. Lamb is thanked for laboratory facili-ties at Glasgow University. Scholarships for D.G.E. Findlay,K.H. Aitken and N.F. Grant from the UK Science ResearchCouncil are gratefully acknowledged as is its funding ofthe associated programme of laboratory work.

on / off

(from controller selector switch)

415 V 3 phase a.c. supply

(from station governor oil pump)contactor

2 hydraulicaccumulators

pump

nonreturnvalve (D)

fromstationprotection

reservoir

drain

emergencyclose

solenoiddump.alve(G)

r—("") alarm

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towater controlvalve

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by-passvalve (C)

1 valve (E )

electro-hydraulicservovalve (F)

by-passvalve (A)

current from•servo controller/servo local control

Originalservo motor(200p.s.i)

Fig. 3 General arrangement of hydraulic servomotor system

servomotorQOOOp.s.i.

position transducer

References

BRYCE G.W., FOORD T.R., MURRAY-SMITH D.J., andAGNEW P.W.: The use of a hybrid computer simulation in theinvestigation of water turbine governors', Simulation CouncilProceedings Series, 1976, 6, (1), pp. 35-44AGNEW P.W., and BRYCE G.W.: 'Optimising turbine operationby electronic governing', Water Power and Dam Construction,1977, 29, (1), p. 36BRYCE G.W. AGNEW P.W., FOORD T.R., WINNING D.J., andMARSHALL A.G.: 'On-site investigation of electrohydraulic

governors for water turbines', Proc. IEE, 1977, 124 • (2),pp. 147-153FINDLAY D.G.E., DA VIE H., FOORD T.R., MARSHALL A.G.,and WINNING D.J.: 'Microprocessor-based adaptive hydro tur-bine governor', IEE Proc. C, Gen., Trans., Distrib., 1980, 127,(5)KERENSKY G., BEVERLY J.C., and CHAPMAN E.J.K.: TheLoch Sloy Hydro-electric Development, Parts I, U and llV,'Proc.I. Mech. E., 1953, 169, pp. 205-232

IEEPROC, Vol. 127, Pt. C, No. 6, NOVEMBER 1980 359