Sealed transformers

Sealed transformers have certain advantages, and an outline is given of various sealing methods available. The internal pressure relations in a particular type of sealed transformer are obtained, taking into account the effect of gas solution in the oil and the chemical reaction of oxygen with the oil. A review of published experimental work shows how the electric strength of oil varies with gas pressure, and the results are applied to the operating conditions met in sealed transformers. It is shown that special precautions must be taken to avoid large negative pressures. The paper concludes by showing the derivation of the equations for pressures and estimating the effect of tank-wall deflection on the pressure.