| 摘要 |
A non-destructive technique for detecting and observing water-tree formation in an electric cable or a sample or model thereof comprises coupling an acoustic detector to the sample of model and observing acoustic signals in the presence of an alternating voltage stress sufficient to create a risk of water tree formation. The presence of water-trees is indicated by aperiodically repeated occurrence under the said electrical stress of acoustic ringdown signals. Observation at frequencies in the range of 20kHz to 2 MHz is appropriate. <IMAGE> |
