phoenics based arc models as a test tool for new design ideas in switching device
DESCRIPTION
PHOENICS Based Arc Models as a Test Tool for New Design Ideas in Switching Device. J D Yan, T M Wong, * X. Ye, * M. Claessens and M T C Fang. Department of Electrical Engineering and Electronics, The University of Liverpool, Liverpool, L69 3GJ, UK - PowerPoint PPT PresentationTRANSCRIPT
CHAM USER MEETING 2006
PHOENICS Based Arc Models as a Test Toolfor New Design Ideas in Switching Device
Department of Electrical Engineering and Electronics,The University of Liverpool, Liverpool, L69 3GJ, UK
* ABB Ltd, High Voltage Products, Fabrikstr. 13a, 5400 Baden, Switzerland
J D Yan, T M Wong, *X. Ye, *M. Claessens and M T C Fang
CHAM USER MEETING 2006
BACKGROUND OF WORK Liverpool group has long been engaged in atmospheric plasma
research in industrial devices such as high voltage switchgear, welding and cutting, material processing and nano-materials production.
PHOENICS has been used in Liverpool for 14 years. Currently we are using version 3.4 and 3.6.1
Cathode
Nozzle
Nozzle
Anode
Temperature (K)
Probe5.0E+22.4E+34.3E+36.2E+38.2E+31.0E+41.2E+41.4E+41.6E+41.8E+42.0E+42.2E+42.3E+42.5E+42.7E+4
Auto-expansion C.B.
Rotary arc C.B.
Microwave Plasma
Welding arc
CHAM USER MEETING 2006
AN EXAMPLE OF CIRCUIT BREAKER At high current, vapour from nozzle surface pumped into storage
volume to form a high pressure reservoir (fig. on right). At current zero, fast gas flow into nozzle quenches the arc, thus
interrupt the current .
Ablating surfaceVapour flows towards storage
-2000
-1500
-1000
-500
0
500
1000
1500
2000
0.020 0.022 0.024 0.026 0.028 0.030 0.032 0.034-80000
-60000
-40000
-20000
0
20000
40000
60000
80000
Current
CHAM USER MEETING 2006
UNDERSTANDING THE KEY MECHANISMS Capability of PHOENICS to handle the implementation. Surface ablation represented by mass, momentum and energy surface
sources. Arc current interact with its magnetic field (Magnetic pinch effect) is
represented by momentum source. Ohmic heating and radiation are treated as volumetric energy sources. Numeric implementation of moving contact (fig. below) and operation
of valves.A A A
1 3 2
1 3 2 Mass, momentum and energy taken away at Time 2 and returned to the evacuated cells at Time 3.
Mass, momentum and energy added to the cells is equal to the amount that disappears when the cells become solid at time 3.
CHAM USER MEETING 2006
DIFFICULTIES WITH ARC MODELLING Temperature in the range from 300K to 35000K and with steep gradient
(upper fig.). Material properties are highly nonlinear. Pressure ranges from 0.2bar to 100bar. Density changed by order of magnitude.
Radiation is operating. Very strong emission and absorption in thin layer. Flow field is very complex (lower fig.). Shock waves exist in part of the
domain. Implications on convergence and relaxation.
S)()V(t
)(
2—D Axisymmetric Arc Model
Equation S Mass of mixture 1 0 0 -momentum (azimuthal)
u l + t rvu + (JB) + viscous terms
z-momentum w l + t -P/z + (JB)z + viscous terms r-momentum v l + t -P/r
ru 2
- (JB)r + viscous terms
Enthalpy h (kl+kt)/cp E2 -q +dP/dt + viscous dissipation PTFE concentration cm (Dl+Dt) 0
CHAM USER MEETING 2006
SPECIAL SCHEMES To improve and maintain convergence, we used a multi-
zone false time step for relaxation of momentum and energy equations. The division of the zones is mainly based on density and energy source term
For heat source:Zone one: 300 ~10000KZone two: >10000K or volume energy source higher than 108 J/(s.m3).
Arc – electrode interaction. Difficulty was that arc did not following the movement of the electrode. Special coding was introduced in ground to tackle this problem.
CHAM USER MEETING 2006
WHAT WE HAVE ACHIEVED
An arc model that applies to a range of industrial plasma devices which produce realistic, reasonable results within acceptable time.
Can simulate the operation of the arcing process and the movement of the mechanical parts.
Implementation of all important physical mechanisms.
Use of Liverpool’s arc model for optimization of design and test of new ideas.
CHAM USER MEETING 2006
VERIFICATION OF RESULTS
Comparison with test results for an auto-expansion circuit breaker.
0.0E+00
5.0E+05
1.0E+06
1.5E+06
2.0E+06
2.5E+06
3.0E+06
3.5E+06
4.0E+06
4.5E+06
0.000 0.010 0.020 0.030 0.040 0.050 0.060 0.070-60000
-40000
-20000
0
20000
40000
60000
80000
Test result
Simulation
Pressure (Pa) Current (A)
Current (A)Current (A)
CHAM USER MEETING 2006
INFLUENCE OF DESIGN PARAMETERS Circuit breaker design is expensive.
To produce results matching measurement is only the first step.
Complicated phenomenon, such as fast pressure transient, was observed and identified as an important aspect of circuit breaker design. Reasons for pressure transient are to be identified.
Aim is to answer the whys and hows in circuit breaker design. For example if we change a design parameter how the arc behaves differently? Beneficial or adverse effects on circuit breaker performance.
CHAM USER MEETING 2006
INFLUENCE OF DESIGN PARAMETERS
Heating chamber
Heating channel
Moving contact
For Case FG holes
For Case FG holes high f
For Case FG holes low f
Results are compared for pressure at point D which is an important location.
CHAM USER MEETING 2006
INFLUENCE OF DESIGN PARAMETERS
Influence of length of heating channel
2.0E+06
2.5E+06
3.0E+06
3.5E+06
4.0E+06
4.5E+06
0.030 0.031 0.032 0.033 0.034-60000
-40000
-20000
0
20000
40000
60000
referenceLength2, constant VSeries6current
Pressure (Pa) Current (A)
Time (s)
Reference case
Arc column shrinks rapidly near current zero, thus creating low pressure region. This process races with gas from high pressure reservoir.
CHAM USER MEETING 2006
INFLUENCE OF DESIGN PARAMETERS
Influence of internal structure
For Case FG holes
For Case FG holes high f
For Case FG holes low f
Pressure (Pa) Current (A)
2.00E+06
2.50E+06
3.00E+06
3.50E+06
4.00E+06
4.50E+06
0.030 0.031 0.031 0.032 0.032 0.033 0.033 0.034 0.034-6.00E+04
-4.00E+04
-2.00E+04
0.00E+00
2.00E+04
4.00E+04
6.00E+04
reference FG holesFG holes high f FG holes, low fcurrent Time (s)
Reference case
CHAM USER MEETING 2006
TO TEST NEW DESIGN IDEAS
GOOD OR BAD IDEAS?
Pressure recording
Pressure recording
Inlet ALink channel
CHAM USER MEETING 2006
TO TEST NEW DESIGN IDEAS
GOOD IDEAS?
2.00E+06
2.50E+06
3.00E+06
3.50E+06
4.00E+06
4.50E+06
0.0280 0.0290 0.0300 0.0310 0.0320 0.0330 0.0340Time (s)
Pres
sure
(Pa)
-6.00E+04
-4.00E+04
-2.00E+04
0.00E+00
2.00E+04
4.00E+04
6.00E+04
Curr
ent (
A)
Buffer-DV-B1ReferenceBuffer-EV-B2Linked buffer-EV-BlockedLinked buffer-EV-ValveCurrent
CHAM USER MEETING 2006
WHAT CAN BE DONE FURTHER
On fundamental level, we need a more accurate radiation model for gas mixture of SF6 and PTFE.
Convergence problem is not fully solved, especially with skewed grids (BFC).
On PHOENICS side, parallel computation for speedy simulation, unstructured grids for 3D simulation.
Associated issues such as calculation of electric field and radiation transfer etc in unstructured grid system.
Post-processing.