ABB’s ‘Easily Transportable’ autotransformer provides the ideal spare for National Grid substations

2003-09-17 - New design 400/132kV three-phase autotransformer breaks down into three single-phase transformers for ease of transportation without requiring a special movement order

ABB has developed a new traffic-friendly ‘Easily Transportable’ design of 400/132kV autotransformer which is much faster and easier to deliver to site, enabling National Grid’s National Stores team to provide a fast response in the event of a substation transformer failure.

The traditional design of 240/276MVA autotransformer has to be delivered as a complete unit with a total weight, including trailer, in excess of 150 tonnes. This requires a special DFT (department for transport) movement order, which takes a minimum of eight weeks to process. In addition, there are many cases where the original transformer was installed 20 to 30 years ago since when installations and bridges on the delivery route have been downgraded and can no longer support the same weight.

ABB has taken a different approach with its new Easily Transportable transformer, which has been designed specifically for use as a spare to be called in to service at short notice. The three-phase transformer breaks down into three single-phase 92MVA transformers, so that the total weight of each transformer and trailer does not exceed 82 tonnes. This arrangement does not need a special movement order so it can be delivered from its storage site as soon as it is needed.

The interconnection between the single phase transformer tertiary windings is by means of an oil filled busduct. The on-load tapchangers are removed for transport and are fitted with plug in connectors for ease of connection during installation.

The transformer cooler bank is designed for the 276MVA rating and for 240MVA where there are restrictions in space the bank can be reduced in size while meeting the required temperature rise guarantees. The cooler bank interconnecting pipe work is designed for installation into an indoor substation in London but can be adapted for differing site configurations.

David Sullivan of ABB Power Technologies said:
“The idea of a three-part transformer is not new in itself. But the challenge has been to develop a design suitable for existing National Grid site conditions that would keep the weight down while maintaining the same rating performance as a conventional design. This required careful selection of the core steel and winding copper wire as well as precision engineering to keep clearances to a minimum. We also spent considerable time working with National Grid to ensure that the unit can be quickly and easily dismantled in storage and then reassembled on site.”

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    New 400/132kV autotransformer - No DfT movement order required

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