An investigation of the factors affecting the growth of bow tie water trees in XLPE insulation systems

This paper reports an investigation into the factors that can affect the growth of water trees in XLPE cables. The assessment of tree growth has been made on standard MV cable designs and manufactured using materials employed for practical applications. The study has focussed on identifying which are the most important tree growth factors and quantifying their relative severity. The method used to assess the propensity for tree growth was electrical ageing in a wet environment followed by an optical quantification of the tree population. Following the assessment of tree growth, selected parameters were employed to establish their effect on the endurance of XLPE insulation. The endurance assessment was made on extruded wire samples which employ square rather than circular conductors. For convenience, these samples are called "square wires"