Dielectric characteristics of static shield for coil-end of gas-insulated transformer

The impulse breakdown characteristics of insulation models simulating static shields for coil ends of SF/sub 6/ gas-insulated transformers are studied. The static shield is composed of a double-covered electrode and a filler between the coverings. If a filler made of elastomer material is fitted closely on the covered electrode to eliminate gas gaps between the filler and the covered electrode, the impulse breakdown voltage of the static shield is higher than with gas gaps. If a low-permittivity filler is used, the impulse breakdown voltage of the static shield is still higher. The breakdown voltage can be explained by considering that the breakdown is caused by small gas gaps between the filler and the covered electrode. The dielectric strength of the coil end can be increased by applying a static shield with an elastomer filler.<
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