1. 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
* ABB Ltd, High Voltage Products, Fabrikstr. 13a, 5400 Baden, Switzerland
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2. 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
Microwave Plasma
Auto-expansion C.B.
Welding arc
Rotary arc C.B.
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3. 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 .
Vapour flows towards storage
Ablating surface
Current
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4. 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
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5. 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.
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2—D Axisymmetric Arc Model

6. 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 ~10000K
Zone 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.
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7. 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.
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8. VERIFICATION OF RESULTS
Current (A)
Pressure (Pa)
Current (A)
Test result
Current (A)
Simulation
Comparison with test results for an auto-expansion circuit breaker.
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9. 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.
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10. INFLUENCE OF DESIGN PARAMETERS
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.
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11. INFLUENCE OF DESIGN PARAMETERS
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.
Influence of length of heating channel
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12. INFLUENCE OF DESIGN PARAMETERS
Pressure (Pa)
Current (A)
Time (s)
Reference case
For Case FG holes
For Case FG holes high f
For Case FG holes low f
Influence of internal structure
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13. TO TEST NEW DESIGN IDEAS
Pressure recording
Inlet A
Link channel
GOOD OR BAD IDEAS?
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14. TO TEST NEW DESIGN IDEAS
GOOD IDEAS?
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15. 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.
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