Electroluminescence and space charge in polymeric insulation

The electroluminescence detection technique was used to determine the light emitted from cross-linked polyethylene (XLPE) cable insulation under high ac fields in high vacuum and pressurized nitrogen. It is shown that unlike the tests in pressurized gas, which always result in a light emission from inside XLPE specimen, the tests in vacuum can lead to light emission from the specimen surface, some distance away from the highest electric field inside the sample. Since the intensity of light emitted from the specimen surface can be significantly higher than the intensity of EL inside the specimen, care must be taken when selecting the experimental conditions for electroluminescence experiments and during interpretation of the test results