The oil and paper of power transformers gradually age and consequently their quality decreases, which has an important effect on the lifetime of the transformer. The aging rate of these two materials depends on the temperature and moisture of the environment. The presence of moisture in a transformer deteriorates transformer insulation by decreasing both its electrical and mechanical strength. Hence, silica gel is used to absorb the water from the existing air between the environment and the expansion tank.
Since the absorption capacity of silica gel decreases over time, it must be restored during the lifetime of the transformer. This paper evaluates the different effects of moisture on transformer insulation and describes a designed system: the automatic silica gel restoration machine. Applying this machine will increase the life of transformer insulation and consequently the duration of its useful life. The article presents some promising patents on life of oil immersed transformers by automatic restoration of silica gel.