Water tree formation and lifetime estimation in 3.3 kV and 6.6 kV XLPE and PE power cables

Insulation of 3.3 kV and 6.6 kV XLPE and PE cables was found to be mechanically stressed by 20 to 100 kg/cm²during the process of water tree formation. Infrared absorption curves change if water trees are created. A mechanism of the generation of water trees is discussed in detail. Critical values to judge the level of insulation quality are recommended as 0.01 ω. F for electrical resistance and 5% for tan δ. A lifetime curve is presented to estimate remaining lifetime of cables with water trees.