Keywords:
electrical engineering, electrical apparatuses, high voltage switchgear, circuit breaker,
fluid mechanics, CFD,
numerical simulations, FEM, FEV, ANSYS, electromagnetic fields, fluid flows, multiphase flows, interactions - coupled tasks
    
Switchgear:
My research work was during my Ph.D. study focused on study, analyse and theoretical modelling of interrupting process of high voltage circuit breakers, especially advanced "self-blast" circuit breakers with gas SF6. The interrupting process was modelled "per partes" as partial physical processes (mathematical models), which were focused on elimination of critical points of successful interruption. In the last years also an overall CFD model with electric arc model was developed and tested.

The used models can be basically divided into several groups:

• models based on gas flow simulation - steady and unsteady gas flow computations with consideration of energy transfer (conduction, convection, radiation), chemical reactions (gas dissociation, PTFE evaporation) and energy source (electric arc).
• models based on electric field computation - computations of electrostatic field with or without space and surface charges.
• models based on gas pressure field and electric field interaction - models based on equations for dielectric stress (theoretical physics level). The dielectric stress of gases can be derived as rate of E/p or E/r, where E is intensity of electric field and p is gas pressure, resp. r is gas density. The temperature field has to be respected.
• "one - dimensional" integral model of interrupting process.
• overall CFD model with electric arc model
  

 
The theoretical models and methods can be also used to optimize other plasma applications, e.g. plasma torch.
 

CFD (one- and multiphase flows and their interaction with other physical fields):
The FLUENT knowledge (FLUENT was used for electric arc model developmnet) is used also for simulation of other problems in different applications. One and more phases flows, often with heat transfer and under different conditions are solved.
As examples can be mentioned: simulation of condensation chamber for high-pressure system of a truck; analyse of distribution transformer cooling in a concrete distribution station; simulation of inner arcing short-circuit in a switching board or simulation of two phase flow in a fabric filter.

Frequent problem is solution of complex processes with interaction of gas or liquid flow with other physical fields. As an example can be mentioned electrostatic precipitator, where is computed electric field of corona discharge with its space charge distribution first and then twophase flow with charging and separation of discrete particles from flowing gas. Further example can be magnetic flow meter with interaction of electromagnetic filed with flowing liquid.

Electromagnetic field:
Regarding necessity of solution of partial tasks related to electromagnetic field, e.g. solution of electric field distribution in quenching chamber of a circuit breaker or magnetic field distribution in a magnetic flow meter, also some other problems based on electromagnetic field are solved. Theoretical simulation in this area led for example to a new rail brake design or improved electromagnetic drives. 
Problems from this area are also submitted in Diploma and Bachelor thesis.