Improved D-C high-potential testing of insulation systems in low- and medium-voltage D-C equipment

Elimination of unexpected breakdowns in d-c high-potential testing is made possible by observing the electrical noise caused by ionization. (The terms ionization and ionization discharges are used as common terminology to refer to charge redistributions as a result of gaseous breakdowns in the insulation systems; see Appendix I. However, it will be more appropriate for the purposes of this paper to include in this term the charge redistributions taking place whenever a minute conducting path on the insulation surface is broken down.) The relative severity of ionization discharges is easily detected by picking up a voltage drop proportional to the current in the test circuit. The high-frequency discharges can then be observed on an oscilloscope screen or measured by other means. It is found that: