The measurement of discharges in dielectrics

The importance is emphasized of being able to differentiate between an increase in the power factor of a dielectric due to gaseous ionization and an increase due to other causes. The necessity of being able to detect discharges before they have caused sufficient damage to give rise to a change in power factor is also pointed out. A description is given of various methods of discharge detection which have been investigated, together with some details of the apparatus finally adopted and used. Methods for eliminating from the measurement all discharges external to the test sample are dealt with in some detail, this being an essential feature of apparatus for use onhigh-voltage testing circuits. The last section of the paper describes some of the practical uses of the apparatus. In the Appendices the various circuit arrangements are examined mathematically, and expressions are evolved for each method which provide the means of converting the readings obtained into the actual high-frequency current flowing in the dielectric.