NonLinear Systems, Inc.
109 Hnath Rd.
Ashford, CT 06278
steven.boggs@nonlinear-systems.com
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     Nonlinear Systems, Inc. conducts computational research with an emphasis on systems with coupled fields and nonlinear material properties such as electric and thermal field-dependent conductivity, dielectric constant, and/or thermal properties.  Nonlinear Systems has developed proprietary software for solution of such systems.  Applications include metal oxide varistors, lightning arresters, nonlinear field grading elements, capacitor dielectrics which include nonlinear fillers, end turn grading of rotating machines, etc.
      Nonlinear Systems, Inc. can also compute dielectric spectra from FEA models of physical systems and can characterize nonlinear dielectrics over a wide range of conditions.
Figure 1.  Arrester temperature during IEC Thermal Stability Type Test.  The plot at the left is just after the 10 s maximum rated current phase of the test.  The dark red elements are MOV's and the orange elements are the heat sinks between them.  The green elements at top and bottom are metal terminal blocks of the arrester.  The maximum temperature is 541 K.  The image second from the left is at 98 s, 28 s into the MCOV (maximum continuous operating voltage) phase of the test during which the power dissipation is much less than during the 10 s maximum rated voltage phase.  Heat is diffusing from the MOV's to the heat sinks, and the maximum temperature has dropped to 510 K.  The image at third from left is at 320 s.  The maximum temperature has dropped to 498 K.  Once the heat sinks have come close to equilibrium with the MOV's their only effect is to increase thee overall heat capacity rather than to absorb heat as a result of a temperature difference.  As a result, their effect is diminished, and the temperature starts to climb, reaching 509 K at 800 s and continuing to rise to thermal runaway.  This computation of the 30 minute IEC thermal stability type test includes the temperature-dependent nonlinear conductivity of the MOV's, radiative and convective heat transfer, etc. and agrees well witih labortory measurements of the conditions under which full scale arresters go unstable.
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