Transformer condition assessment with the Tettex recovery voltage method

All oil-paper transformers contain some water in their solid insulation. The Tettex Recovery Voltage Meter (RVM) is a method for determining the moisture content in the paper so that the effects on dielectric integrity, loading capability and residual life expectancy can be estimated. The author discusses the problems of moisture in paper insulation, the polarisation effects and polarisation spectrum measurement using the Tettex RVM. Practical applications of the method are outlined and it is compared with other methods