Patent ID: 8607813

Claim:
A method for reducing the air present in a high voltage power plant comprising: providing an apparatus comprising: an expansion vessel having a volume partially filled with an insulating liquid, at least a portion of a remainder of the expansion vessel volume being a space for retaining air from the atmosphere, a first tank and a second tank positioned inside of and being smaller than the first tank, the first tank and second tank having lids at the tops thereof, the first tank and second tank having a volume partially filled with a diffusion barrier liquid, the first and second tank having a common opening located below a fill line of the diffusion barrier liquid for permitting the movement of liquid between the first and second tank, the first tank having an external buffer space present in a portion of a remainder of the volume of the first tank, the second tank having a compensation space present in a portion of a remainder of the volume of the second tank, a flow line between the space for retaining air from the atmosphere in the expansion vessel and the external buffer space in the first tank, a compensation flow line between an ambient atmospheric environment and the compensation space in the second tank, a pipe positioned in the second tank for permitting air flow between the compensation space and the diffusion barrier liquid; whereby the diffusion barrier liquid provides a barrier to diffusion of at least the oxygen component of air from an atmosphere side of the diffusion barrier liquid to the external buffer space on an expansion vessel side of the diffusion barrier liquid; determining the volume of the external buffer space through predetermined designation of an upper working temperature and a lower working temperature of the insulating liquid; transferring gas in the space in the expansion vessel to the external buffer space up to a predetermined overpressure relative to atmospheric pressure; transferring gas from the external buffer space to the expansion vessel until attaining a predefined value of underpressure relative to atmospheric pressure; releasing gas from the external buffer space in the first tank when the predefined overpressure value is exceeded through displacement of the diffusion barrier liquid in the first tank though the pipe in the second tank; and drawing gas into the external buffer space from the atmosphere into the first and second tank though the compensation flow line when the pressure in the external buffer space falls below the predefined underpressure value.