Investigation of the Influence of Plastic Evaporation on Pressure Rise due to Fault Arcs in Electrical Installations


  • S. Wetzeler
  • G. J. Pietsch


Internal arcs, plastic evaporation, pressure calculations


Internal arcs in electrical installations cause a sudden pressure rise due to heating of the gas surrounding
the arc. The pressure rise may endanger personnel, the electrical installation and even the switchgear
building. Based on the need to design switchgear more compact, plastic materials are used. The interaction
of the arc with these materials releases gases by evaporation and thereby influences the pressure rise
within the installation as well as the energy balance of the arc. In order to analyse these effects in detail,
some commonly used plastics are exposed to a high current arc. In this contribution the pressure development
in a closed vessel equipped with different plastic materials, their mass losses and the portion of
electrical energy causing overpressure, known as thermal transfer coefficient or kp–factor, are determined
at three values of the filling pressure of the vessel. The plastic materials under investigation are epoxy,
polyamide 6.6, polybutyleneterephtalate, polycarbonate and silicone rubber. With the information provided,
the influence of the different plastics on pressure development can be predicted.


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