Dry-type transformers are inherently more reliable than oil cooled units, offering higher levels of uptime. This is mainly the result of having no oil in the system, as this oil must be regularly sampled and tested as part of a maintenance programme. The reliability of oil cooled transformers can be severely undermined if this maintenance is not systematically conducted. As the oil degrades over time, its cooling capacity reduces and affects equipment performance and lifespan.
In contrast, a dry-type transformer needs only an annual inspection to check for conditions such as dust build-up. This can be easily attended to with compressed air, which clears the dust until the next visit. Maintenance cycles for oil cooled transformers are usually quarterly, and must also include the repair of leaks – which can be costly and time consuming.
