Why should oil immersed transformer cores not be exposed to air for too long? What if I want to extend it?
The main purpose of controlling the exposure time of oil immersed transformer cores in the air is to prevent the insulation of oil immersed transformer cores from getting damp.
To shorten the exposure time of the core in the air, oil can be added from the top and poured around the core during refueling (35kV and below oil immersed transformers), so that the insulation of the core is washed away by the oil. At this time, the oil immersed transformer can be considered isolated from the air. If the air is dry and the relative humidity is below 50%, the exposure time to the air can be relatively prolonged. If the humidity is 80% or above, some heating devices can be installed around the core (clean heat sources such as electric heating should be used), or construction can be carried out. If the core winding can be heated up (with an appropriate current), the exposure time can also be extended.
The exposure time is related to the above factors, and there is no mechanical requirement to limit it to a few hours.
