Computer Simulation of HV Circuit Breaker Interruption_EnergoBos ILJIN February 2015

EnergoBos ILJIN d.o.o. Sarajevo

Computer simulation of HV circuit breaker interruption

>> HV CB Simulation


Contents

Introduction

Main application diagram

The program Main and Log On form

Modules

Input data

The travel measurement system and control

Main calculation flow chart

Gas flow - universal model

Driving mechanism - universal model

Results & verification

Program results combined with other calculations

Conclusion2


Introduction

Computer simulation is aan economic way in research and development of modern SF6 circuit breakers.

Work on computer simulations started on early 80 used first available PCs and simple Basic programming language.

With limited number of short circuit tests and results of those tests, program can help us with:- prediction of interruptions for other arcing times and other values of short circuit currents- calculation of interaction between interrupting unit and driving mechanism- optimization of an existing interrupting unit and driving mechanism- calculate influence of any design changes on circuit breaker performance- calculation of state of SF6 gas in circuit breaker chambers- electric arc influence on gas mass flow- pressure build up calculation- nozzle ablation- contact erosion- driving mechanism behavior during interruption of high short circuit currents...

Program can not predict result of interruption in advance, but program results combined with other calculations can help us in this.

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Main application diagram

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The program Main and Log On forms

Main mask

The program consists the following modules: New-Open-Save-Exit module, Interrupter unit, Driving mechanism-Travel, Gas SF6, Electrical current, Data analysis, Calculation-Automatic calculationEB measurement system control

Log On form

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Modules

New Open Save Exit module (clear open - save all input data about circuit breaker and close program)Interrupter unit (interrupter unit geometry, nozzle ablation, contact erosion, heating and cooling of interrupter unit chambers)

Driving mechanism Travel (coordinates, lengths, angles, masses and moments of inertia of mechanical parts, kinematic calculations, compression force calculation, data about spring(s), calculation of opening, single or three phase operated, using experimental travel instead mechanism simulation, model of shock absorber, double speed model)Gas SF6 (equations of state, thermodynamic characteristics of SF6 gas, gas flow process, calculation of state of SF6 gas in all interrupter chambers)

Electrical current (analytical presentation of single or three phase short circuit currents, model of synthetic circuit: serial and parallel with current injection, data from experiment used as input data in calculation)Data Analysis (graphical representation of program results and experimental results, open & save results, comparison between calculated i measured results)

Calculation Automatic calculation (more then 240 simulation results)Vbd (breakdown voltage estimation, visualization of dielectric stresses inside a circuit breaker nozzle)

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Input data interrupter unit

Nozzle and arcing contact geometry - input data

Gas properties input data

SF6 gas equation of state

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Input data driving mechanism

Spring - input data

Absorber input data

Mechanism geometry input data

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Input data electrical current

The arc model - simple integral arc model: modified Frost Liebermans enthalpy flow arc model, system of equations, thermodynamic characteristics of SF6 plasma, arc voltage and arc diameter, input of data from experiments

Electrical current

The arc model

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The travel measurement system and control module implemented in HV CB Simulation

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This form is used to prepare, initialize, activate and to control EBs travel measurement system and the test object.

Loading, digital post-processing and filtering of raw measurement data is also implemented. Additionally, information about specific travel-related parameters are being calculated and displayed for each travel record.


HV CB Simulation User Manual, Technical Manual and Input Data Description

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Main calculation flow chart

YES

NO

NO

YES

YES

YES

NO

NONEW STEP

START

Set up for initial variablesSTEP = 0

New nozzle?

Nozzle discretization

Experimental

travel?

STEP = STEP + 1

Mechanism calculations

SF6 gas state in all chambers after

contact movement

Calculation of cross sections between

chambers

SF6 gas mass flow between all chambers

SF6 gas state after cooling of SF6 gas

SF6 gas state in all chambers after inflow/outflow

Current?

State of SF6 gas after ablated and eroded

material inflow

Nozzle ablation,contact erosion

State of SF6 gas in chambers after heat input from the arc

Arc current, voltage, diameter

Data output

End ofoperation

?

END

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Gas flow universal model

Defining interrupter unit chambers and connections between them Matrix of coincidence

- Universality- Easy scheme drawing for any type of SF6 interrupter- Calculation of state of SF6 gas (pressure, temperature, density...) in all interrupter chambers- Calculation of gas flow for every SF6 interrupter with a known geometry configuration

V12 V22 V13 V23 V25 V24

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Driving mechanism universal model

Total energy in the system:

Spring energy:

Absorber energy:

Friction energy:

Compression energy:

Compression force:

Reducted coefficients:

Reduced mass:

Speed:

Travel:

)()()()()( tEtEtEtEtE ncompressiofrictionabsorberspring

)))(())(((21)( 20

20 lttlltlktEspring

))()(())(),(()()( tththtvthFttEtE absorberabsorberabsorber

))()(())(()()( tthththFttEtE frictionfrictionfriction

))()(()),(()()( tththtthFttEtE ncompressioncompressioncompressio

i j

jjiij

ji

incompressio StthpStthptthFntthFpF )),(()),(()),(()),((

)()())((

tvtvthr ii )(

)())((tvttho ii

j

jji

iired thoIthrmthm22 ))(())(())((

))(()(2)(thmtEtv

red

ttvtthdttvth )()()()(

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Comparison (no load)between experimental And calculated travel and speed (puffer type)

Comparison (on load three phase 40 kA)between experimental And calculated travel and speed (puffer type)

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Comparison (no load)between experimental And calculated travel and speed (self-blast type)

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Results of the simulation: Temperature of SF6 gas in heating chamber, Pressure of SF6 gas in heating chamber, Gas mass flow through minimal cross section in main nozzle, Arc voltage, Arc energy, Totoal nozzle ablation mass, Arc cros-section at 1 st arcing contact.

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Comparison between experimental and calculated pressure (peak value) in

thermal chamber

Test No:

GCB 245 kV 40 kA, SLF tests

Breaking current, rms [kA]

Arc duration

[ms]

Max pressure

Experiment [MPa]

Max pressure

Calculation [MPa]

1. 31.9 11.6 - 3.9522. 31.9 11.6 3.89 3.8883. 32.3 10.6 3.98 3.6944. 35.5 10.4 4.06 4.090

Pressure rise in thermal chamber, L90 test No 4, experiment versus calculation

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Calculated (vertical) and measured (horizontal) mass loss of main nozzle

Calculated (vertical) and measured (horizontal) increase in main nozzle throat diameter

Calculated (vertical) and measured (horizontal) increase in auxiliary nozzle throat diameter

Main nozzle cross section, calculation and experiment, T100s phase C

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0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

Jan Osc4038

Jan Osc4039

Jan Osc4040

Jan Osc4041

Feb Osc4006

Feb Osc4007

Feb Osc4008

Feb Osc4009

Feb Osc4014

Feb Osc4015

Rastojanje kontakataPritisakMaseni protok

With limited number of short circuit tests and results of those tests, program can help us with prediction of interruptions forother arcing times and other values ofshort circuit currents.

Pressure, gas mass flow and arccontact distance at CZ

Determination of critical values of characteristic quantities

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Program results combined with other calculationsPrediction of thermal breakdown

4. MatLAB simulation

Model verification

1. Computer simulation 2. Calculation of parameters

Characteristic quantities

Parametersblack box

model

3. Composite black box model

5. Results of MatLAB simulation and CZ measurement

P1, t1P2. t2P3, t3

P, l, Mg

Geometrija sklopnog elementaPodaci o pogonskom mehanizmuPodaci o mediju za gaenje (SF6)Podaci o elektrinoj strujiP R O R A U N...........................................................

Source: Correlation of Black Box and Integral Physical Arc Model Parameters for a Real SF6 Circuit-Breaker,Doctoral disertation, Almir Ahmethodi, Faculty of electrical engeering Sarajevo

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Program results combined with other calculationsPrediction of thermal breakdown

Quantitatively :The accuracy of prediction of success of the interruption

Source: Correlation of Black Box and Integral Physical Arc Model Parameters for a Real SF6 Circuit-Breaker,Doctoral disertation, Almir Ahmethodi, Faculty of electrical engeering Sarajevo

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2

90

Correct prediction in 18 out of 20 cases

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HV CB Simulation results combined with other calculations (CFD, Electrical field calculation...) - Breakdown voltage estimation procedure

Circuit breakerdesign

HV CB Simulation

Electric fieldcalculation

CFD

HV CB Simulation results as initial conditions for

CFD (p0, T0, 0)

BREAKDOWN

E field calculation results (E) CFD Results (p, T, )

Breakdown voltageUbd=f(E, )

Uapplied > U bdNO

YES

NO BREAKDOWN

Next project phase23


Breakdown withstand voltage estimation procedure

Recovery voltage in time (capacitive current interruption):

Breakdown voltage in time:

CFD

E field24


... ...

Breakdown withstand voltage estimation results and animation

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Conclusion

General lack of knowledge and experts for arc modeling and the simulation of high voltage SF6 circuit breakers is already evident.

A team for arc modeling and the simulation of high voltage SF6 circuit breakers consisting of some dozen experts is very expensive for any company in the world.

The idea is to organize a team which will continuously work on arc modeling and the simulation of high voltage SF6 circuit breakers with the support of several companies interested in the project.

The Team will treat fairly all companies and we do commit ourselves to the highest ethical and professional codes.

Our goal is a universal software to provide calculations and simulations of high voltage circuit breaker interruption for diffrent companies in the world,

and why not even for YOUR COMPANY?

All we need is:kinematic chain data (coordinates, angles, lengths, masses and moments of inertia),spring and absorber characteristics,volumes of interrupter unit chambers and cross sections between them,nozzle and arcing contact geometry ...

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Computer Simulation of HV Circuit Breaker Interruption_EnergoBos ILJIN February 2015

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