Method for reducing the air feed from the atmosphere into the expansion vessel of high-voltage systems filled with insulating liquid and device for carrying out the method

Abstract

A method and apparatus are provided for reducing the oxygen content drawn from the atmosphere that enters the insulating fluid-containing expansion vessel of high-voltage systems. The apparatus is provided with inner and outer tanks that include a liquid that provides a diffusion barrier for capturing oxygen from the atmosphere. The tanks are in communication with the atmosphere on one side of the barrier and in communication with the expansion vessel on the other side of the barrier. Further provided is a moisture-capturing dehumidifier upstream of the diffusion barrier to dry the gas passing into the expansion vessel. The apparatus limits degradation of the insulation system caused by moisture and oxygen, thereby increasing the life span of the high-voltage system. In the method, gas is transferred from the expansion vessel to an external buffer space in the outer tank up to a pre-defined overpressure relative to atmospheric pressure, said gas being discharged to the atmosphere only when the pre-defined overpressure is exceeded. Further, gas is transferred from the external buffer space to the expansion vessel to approach to a pre-defined underpressure relative to atmospheric pressure, with either air from the atmosphere or inert gas being fed to the buffer space when pressure drops below the underpressure. The buffer space volume is correlated to lower and upper working temperatures of the insulating fluid in the high-voltage system, which temperatures are determined based on the geographical location of the system.