Finite Element Analysis on Forces, Currents, and Magnetic Fluxes of Misaligned GIS Disconnector

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This paper provides an effective misalignment fault diagnosis method of the gas-insulated switchgear (GIS) disconnector. Relationships between contact forces and the surrounding magnetic field in various mechanical assembly conditions were studied by the 3-D electromagnetic-mechanical coupled finite-element model and physical experiments. First, spring deformation and contact forces on individual contact elements were obtained by mechanical field analysis. Holding springs were modeled by equivalent elastic rings during analysis. Second, the magnetic field around the GIS disconnector was obtained by electromagnetic-field analysis. Contact resistances on contact interfaces were modeled by cylindrical bridges, which use mechanical contact forces as parameter inputs. Physical tests have been carried on the prototype GIS disconnector with various artificial misalignment faults. In different situations of misalignment faults under ac current, surrounding magnetic flux densities were measured by the Hall sensor array. Calculated and measured results have the same trend that the mechanical misalignment fault could change distributions of contact forces then make distortion of currents and the surrounding magnetic field. Magnetic-field behaviors of the GIS disconnector with different mechanical assembly conditions were studied. The results show that the deviation of magnetic flux density becomes larger while reducing holding spring stiffness, decreasing movable conductor insert depth, and increasing the movable conductor docking angle.