MODELLING OF LARGE SYNCHRONOUS GENERATOR AND CALCULATING THE AUTO RECLOSURE TIMING

MODELLING OF a LARGE SYNCHRONOUS GENERATOR AND computation of THE AUTO RECLOSing TIMING of the circuit breaker for its transient stability.M.TECH THESIS MID-TERM REVIEWGAURAV RAI GUIDE-Dr.D.N.BADODKARSO/C HEAD,DRHR,BARC.OCES-57th BATCH TECH.ADIVISER-V.SANKARANARAYANANNPCIL SO/H,Engg.(Elect.)-LWR NPCIL.

Presentation itineraryTHESIS IN BREIFWORK DONELITERATURE SURVEYDATA COLLECTIONSIMULATIONWORK ENVISAGED IN FUTUREMODIFICATIONS/CHANGES PROPOSED IN THE THESIS

PROJECT IN BREIFThe thesis envisages to model a large Synchronous Generator along with the necessary systems like the turbine, governor and automatic voltage regulator etc.

The generator will be synchronised to the grid via a circuit breaker and a generator transformer.

The software being used for this purpose is PSCAD which is an electrical simulation software with rich library of electrical equipment.

The simulation of the Synchronous Generator will pave way for study of transient behaviour of this large synchronous generator by simulating a fault at the generator terminals.

Now further, auto-reclosing timing computations will be done for transient stability of the Synchronous Generator.The possible effects of using auto-reclosing scheme on a large synchronous generator is also envisaged to be studied in this thesis.

Insulation coordination study from the generator terminals to the outgoing transmission lines for incoming and internal surge sources is also proposed to be analyzed in this thesis.How software modelling is performedPSCAD (Power Systems Computer Aided Design) is a powerful and flexible graphical user interface to the world-renowned, EMTDC electromagnetic transient simulation engine. PSCAD enables the user to schematically construct a circuit, run a simulation, analyse the results, and manage the data in a completely integrated, graphical environment. Online plotting functions, controls and meters are also included, enabling the user to alter system parameters during a simulation run, and thereby view the effects while the simulation is in progress.EMTDC is an iterative solution engine used in PSCAD for the solution of the differential equations. It is a kind of EMTP(Electromagnetic Transient Program) which has been widely used by electrical engineers around the world to solve power system transient stability studies. continued....The software uses various mathematical techniques for modelling the electrical equipment.The Synchronous Generator is being modelled using Dq0 transformation.The induction motor is also modelled using the same mathematical technique.The transformers are modelled as a reactance.The circuit breaker is modelled as a high resistor when in tripped condition otherwise a low resistance.The transmission lines are developed based on Bergeron model.

SIMPLIFIED BLOCK DIAGRAM OF THE MODELSy.G.AVRTURBINEGOVERNORGTGCBGRIDAUXILIARY LOADWORK done till now- simulationThe stand alone generator model has been developed.The data for the modelling of this large synchronous generator has been taken from the currently operating NPCIL plants and the manufacturers such as Schneider and Alstom.To make the generator more realistic and practical in its response towards any kind of transient being simulated to test its stability, the standard exciter and voltage regulator has also been used to control the excitation based on loading the Generator.The auxiliary power supply and loads which are necessary for any nuclear power producing entity system has also been developed where the auxiliary load is 6% of the rated capacity of the generator.The approach employed towards the development of the model of a large synchronous generator and its associated system has been of that of a block diagram technique. This is done to ensure proper clarity in the model once completed.To explain the approach here is an example:- the generator has been developed and modelled separately and has been integrated to the rest of the system via a block which is named as GeneratorSimilarly for others.After stand alone modelling , the different equipments were integrated together and their synchronism was checked.The rest is visible from the simulation snapshots.

Typical data used for some equipmentSynchronous Generator ParametersValue of the parameterPower 1000MWeVoltage 24kVCurrent in stator26.75kAOperating Power Factor(envisaged)0.9frequency50HzRotor speed of rotation3000rpmEfficiency 95%Generator TransformerValue of the parametersVoltage ratio24/400kVRating 3x417MVAImpedance rating 14%Typical load considered(hv motor)Value of the parameterOperating voltage6kVType of motor Induction Motor(Squirrel Cage)Power rating7MWeSpeed of operation3000rpmNumber of poles6Model of the Synchronous generator and a test run results

Work envisaged in futureOptimizing the model to reach a practical values of power factor and other parameters to suit our purpose.Simulating one of the following faults to test the Synchronous Generators stability towards the transients: loss of excitation faultLoss of synchronism Negative phase sequencingAnalysing the behaviour of the Synchronous Generator towards these transient conditions.Study of the auto reclosing schemeCalculating of the auto reclosing timing for the stability of the Synchronous Generator.Modifications in the thesis envisaged

It is hereby humbly brought to the notice of the committee members that it has taken almost three and a half months to develop and integrate the model of Synchronous Generator with its associated systems.The job of optimising the model is still under process.The various tasks envisaged in the earlier slides can be taken up once this is done.So it is hereby proposed that INSULATION COORDINATION study as proposed in the initial stages, might not be taken up for this thesis due to lack of time and the quantum of work still pending. Thank you for your precious time.REFERENCES USED IN THE THESISMODELLING OF THE SYNCHRONOUS GENERATORIEEE Guide for Synchronous Generator Modeling Practices in Stability Analyses, IEEE-1110SYNCHRONOUS MACHINE THEORY AND MODELLING, P. KONDURDQ TRANSFORMTIONS:IEEE Guide for Synchronous Generator Modeling Practices in Stability Analyses, IEEE-1110SYNCHRONOUS MACHINE THEORY AND MODELLING, P. KONDUR

Cylindrical rotor machine

Advantages of DQ transformationAll inductances are independent of rotor position (except for the effects of magnetic saturation)Under balanced steady state operation, the stator quantities appear as dc quantitiesTime varying three-phase stator voltages, currents, and flux linkages were also transformed into time invariant direct and quadrature axis quantities under steady-state conditions.During electromechanical transient conditions, stator quantities vary slowly with frequencies in the range of 1.0 to 3.0 HzThe above simply calculations and computationsP.U. Machine Equations in dqo reference frame

Stator and rotor emf equations in dq transformations