Topping up transformers following maintenance

A UK Distribution Network Operator (DNO) needed to remove some oil from the top of a 132kV transformer to inspect the top of the transformer core and windings following an alert on their Dissolved Gas Analysis report.
Because the core and windings had been exposed to atmosphere, albeit for a fairly short time it was considered best engineering practise to top up the transformer via a Mobile Processing Unit (MPU) to ensure maximum dryness of the oil. Subsequent circulation of the oil volume through the MPU would then ensure overall dryness and pick up on any inadvertent contamination introduced during the internal inspection.

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