| This is a large transformer damaged by the March 1989 superstorm at a nuclear plant on the Delaware River in New Jersey. This unit is one phase of a 1200 MVA bank of three transformers. These very large transformers can cost up to $10 million and when damaged, remanufacture and replacement can take up to a year. This can result in an outage to the entire plant for the duration of the repair if a replacement is not readily available. In this case, an identical transformer from a canceled nuclear plant was obtained and the new transformer and plant were placed back in service after only a six week outage. The lost production from the plant cost customers up to $400,000 per day. |
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| These pictures show the internal damage that occurred in this transformer from Geomagnetic Induced Current (GIC). The presence of GIC causes saturation of the core steel of a transformer and creates stray
flux that can be so intense it creates hot spots in regions
of high flux concentration. |
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| In this slide the heating was so intense that
it not only burned through the paper winding insulation but it melted some
of the large copper strands in this 3,000 amp winding lead. |
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In this slide are areas of heating related insulation damage on large current carrying windings in the transformer. All of these areas under normal operation are contained in an oil-immersed bath that normally provides sufficient cooling and dielectric insulation. Damage this extensive requires a considerable amount of heating. |
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