Insulating paper

Three doctoral theses prepared at the Institute of Paper Chemistry and based on investigations of the power factor and dielectric strength of insulating papers are summarized by J. A. Van den Akker¹. In order to study variables affecting power factor of paper dielectrics an apparatus has been devised by means of which a condenser made from test sheets of paper can first be thoroughly dried under vacuum and the power factor determined at various pressures and temperatures. One of the features of this apparatus is a device employing a spirit level for accurately measuring electrode spacing. Flushing the test chamber with dry nitrogen at intervals while drying had no effect on the final power factor of the sample though equilibrium was attained in a slightly shorter time.