Tap changer assembly and a transformer tank assembly

A tap changer assembly comprising a tap changer assembly housing completely enclosing a tap changer volume and an overflow volume, respectively, said tap changer assembly further comprising at least a part of a tap changer located in said tap changer volume, said tap changer volume and said overflow volume being connectable to each other via an overflow assembly,

• such that said overflow assembly is such that:
• when a pressure in said tap changer volume is lower than a predetermined overflow pressure threshold, fluid communication between said tap changer volume and said overflow volume via said overflow assembly is prevented and
• when said pressure in said tap changer volume is equal to or higher than said predetermined overflow pressure threshold, fluid communication between said tap changer volume and said overflow volume via said overflow assembly is enabled,
• the tap changer volume and the overflow volume being aligned along an axis, the tap changer assembly housing having a largest internal cross-sectional area, enclosing said tap changer volume, orthogonal to the axis, and, when fluid communication between said tap changer volume and said overflow volume via said overflow assembly is enabled, an area at least 10% of said largest internal cross-sectional area between the tap changer volume and the overflow volume is enabled for fluid communication via said overflow assembly, and the overflow assembly comprising a fluid passage which is closed by a biased cover when fluid communication between said tap changer volume and said overflow volume is prevented, and which fluid passage is open when fluid communication between said tap changer volume and said overflow volume is enabled.