Leakage-Voltage Characteristics of Insulation Related to D-C Dielectric Strength [includes discussion]

The leakage-voltage characteristics of several dry-type insulating materials in the form of sheets, tapes, and insulated bar specimens were investigated. Electrode arrangements were such that conditions of volume leakage, surface creepage, and combinations of both were observed. The characteristics thus obtained were plotted and the accuracy of breakdown forecast, based on extrapolation of this curve, was observed. Based on these tests and the results of work reported by other investigators, some conclusions are drawn relative to the possible usefulness of this test method in forecasting nondestructively the breakdown of machine insulation.