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Which insulating mediums absorb moisture?

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    Which insulating mediums absorb moisture?

    Which insulating medium most readily absorbs and holds a large quantity of moisture?

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  3. LearningisNETA is offline Junior Member Pro Subscriber
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    Silicone

    Silicone apparently

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    Silicone fluids behave similarly to mineral oils and askarels with respect to transport of moisture into the transformer insulation. However, the saturation and equilibrium condition of silicone fluids with insulation may be quite different from the other fluids. It is often more meaningful to consider the steady-state water content of the system than the water content of the fluid alone. Water is the baseline for specific gravity, meaning it has a value of 1.0. Silicone could have a specific gravity of 0.98. In theory, water should still settle to the bottom of the tank, but could be more apt to move around the tank the closer the specific gravity is to water.

    Silicone has a higher saturation content than askarel or mineral oil. This is significant because some dielectric properties deteriorate rapidly in the presence of moisture. Despite its higher water content at saturation, silicone fluid maintains good dielectric properties at much higher water levels than askarel or mineral oil.

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    Paper is an often used insulator, which absorbs water

    Quote Originally Posted by LearningisNETA View Post
    Silicone apparently
    Seems to me that if the choice was available, paper insulation (even if soaked in oil) will absorb water much more than silicone.

    Did the question include paper in the choices? Paper is still used extensively in transformer insulation and was used years ago for medium voltage cable insulation. There's thousands of miles of such PILC cable still in operation.

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    Quote Originally Posted by gchoquette View Post
    Seems to me that if the choice was available, paper insulation (even if soaked in oil) will absorb water much more than silicone.

    Did the question include paper in the choices? Paper is still used extensively in transformer insulation and was used years ago for medium voltage cable insulation. There's thousands of miles of such PILC cable still in operation.
    Paper would be a good choice. It does absorb moisture. As a transformer heats up, the moisture is expelled from the transformer paper. As it cools down, the water is absorbed back in the paper. Good idea!

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    Quote Originally Posted by ElectricalTestTech View Post
    Paper would be a good choice. Good idea!
    I definitely don't want credit. It's not my idea.

    99.9% of transformers are paper insulated.
    Some smaller transformers, such as PT's, are cast in resin.

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    Quote Originally Posted by gchoquette View Post
    I definitely don't want credit. It's not my idea.

    99.9% of transformers are paper insulated.
    Some smaller transformers, such as PT's, are cast in resin.
    Well, the unfortunate part about vague questions is that they can be interpreted so many ways. I was thinking along the lines of liquid, but paper is definitely a valid option. All oil filled transformers have paper in them

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    Quote Originally Posted by gchoquette View Post
    Seems to me that if the choice was available, paper insulation (even if soaked in oil) will absorb water much more than silicone.

    Did the question include paper in the choices? Paper is still used extensively in transformer insulation and was used years ago for medium voltage cable insulation. There's thousands of miles of such PILC cable still in operation.
    If its an available choice, go with paper or cellulose insulation. Otherwise I'm with ETT on Silicone being the next closest choice, theory being that its specific gravity at 0.98 is closest to water. I also remember reading somewhere that Silicone can absorb moisture from the atmosphere so you should be extra careful to keep it isolated from air when pumping it.

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