Generalized Mayr Model for Arcs in MV Switches With Splitter Plates

Abstract

The effect of splitter plates (SP) on current interruption at medium voltage (MV) level is theoretically investigated in the framework of Mayr&#x0027;s arc model, which is generalized to take into account the electrode fall voltage, <i>V</i>₀, of the SP. The model is analytically solved in the current zero (CZ) region where the current (before CZ) and the voltage (after CZ) can be linearized with respect to time. The current turns out to be successfully interrupted if the total electrode fall voltage, <i>NV</i>₀, for <i>N</i>&#x00A0;&#x2212;&#x00A0;1 SP plus contact electrodes, is larger than twice the transient recovery voltage, <inline-formula><tex-math notation="LaTeX">${\boldsymbol{U}} \approx {\dot{\boldsymbol{U}t}}$</tex-math></inline-formula>, at the characteristic arc decay time, <i>t &#x003D; &#x03C4;</i>, after CZ: <inline-formula><tex-math notation="LaTeX">${\boldsymbol{N}}{{\boldsymbol{V}}_0} &gt; 2{\dot{\boldsymbol{U}\tau }}$</tex-math></inline-formula>. For <inline-formula><tex-math notation="LaTeX">${\boldsymbol{N}}{{\boldsymbol{V}}_0} &lt; 2{\dot{\boldsymbol{U}\tau }}$</tex-math></inline-formula>, an additional thermal condition must be satisfied, where also the current rate, <inline-formula><tex-math notation="LaTeX">${\dot{\boldsymbol{I}}} = {\boldsymbol{\ dI}}/{\boldsymbol{dt}}$</tex-math></inline-formula> before CZ, and the arc cooling power, <i>K</i>, are involved. The intuitive results lead to a simple understanding of the electrical effect of SP on current interruption at MV and serve as an initial design rule for the number of SP in different gases.