Water treeing in XLPE

Water treeing in underground HV power cables initiates in all solid dielectric materials from sites of high electrical stress such as rough interfaces, protruding conductive points, voids or imbedded contaminants. Water treeing is characterized by: (1) foundation of moisture or water is essential for the water growth; (2) water treeing can grow in the underground cables for years before reaching a size where it may contribute to breakdown; (3)the applied voltage required for water treeing initiation is much lower than that required for the development of electrical trees, and (4) the growth of water trees is accelerated under frequency, no water trees generate under DC voltage. It was reported that at frequencies from 6 kHZ to 10 kHZ trees could be grown in less than 30 days which would normally have required years to grow under service conditions