Trapped charge-induced field distortion on GIS spacers

Operation of GIS (gas insulated substations) disconnecters can leave a DC voltage (electric field) on the switchgear which can cause charging of spacer surfaces. Analysis indicates that the surface charge density is related to the voltage-induced field. The charge distribution is likely to take the form of a strip, with a sharp termination of the charge density at one end which can result in a substantial field enhancement which adds to the field induced by the disconnector upon closing and increases the probability of a surface flashover when the disconnector is closed. This may explain failures in some early 550 kV disconnector designs.<
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