By actual measurement, low frequency magnetic field distributions in the multiple unit train were obtained. The data shows that the field is in the permission range as a special industrial environment according to international low frequency magnetic field standards and GB 9175-88. Taken into account of the multiple unit train's specific electrical structures (including overhead contact system, car roof, windows and rail), pantograph catenary arc's low frequency field emission modeling and mechanism analysis were completed. Thus, we get the LF magnetic field distribution regularity and prove that the interior intense magnetic field in the multiple unit train mainly derives from the window current induction. Moreover, a pantograph catenary contact loss criterion is proposed in terms of magnetic field probability.

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When solving electromagnetic scattering problem with T-matrix method, if the scattering obstacles have point-group symmetry, i.e. remaining unchanged under the group transformation, we can obtain the relationship between geometric symmetry and symmetry of elements in T matrix by the usage of group theory. In this way we can foresee the exact values of some matrix elements, as well as relations between elements, which would save numerous running time in numerical calculation.

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