ASTM D6097 covers the relative resistance to vented water-tree growth in solid translucent thermoplastic or crosslinked electrical insulating materials, especially applicable to extruded polymeric insulation used in medium-voltage cables.
The test method subjects insulation specimens to simultaneous electrical stress and moisture exposure over extended periods. Water trees are microscopic damage patterns that grow from surface defects or contaminants into the insulation.
After the test period, specimens are examined optically for water tree growth. The length and density of water trees are measured to characterize the material’s relative resistance to this degradation mechanism, critical for predicting long-term reliability of cable insulation.