Water Tree in XLPE Cable.

What is Water Tree?

Water tree degradation is a major problem for medium voltage XLPE cables. One the Most important degradation process of the polymeric insulation that contributes to the failure of the cable

Why it call Water Tree? 

Water Trees are  a diffuse structure in the polymer resembling the shape of a tree or bush.

How it cause?
Water Tree are formed and grow in the presence of moisture, impurities or contamination@ and electric field over time.

There are generally two types of water trees, namely; )

Bow-Tie Tree

Vented Trees

Water Treeing - Bow-Tie tree

Bow-Tie trees are water trees that grows from the insulation outwards towards the surfaces of the insulation.

These trees grow in the direction of the electric field in both directions, towards the two electrodes.

Bow-Tie trees have faster initial growth rate as compared to vented trees.

Bow-Tie trees are however, not capable to growing to large sizes and usually do not grow to a size significant enough to cause failure of   the insulation

Water Treeing – Vented tree

Vented Tree are water trees that grows from the surface of the polymer inwards into the insulation  system.

 These trees will grow in the direction of the electric field.

 Vented trees have lower initial growth rate as   compared to bow-tie tree

 Vented trees are capable of growing right through the   entire insulation thickness.

 This is the more venomous of the two trees as these trees as it is of bridging the insulation system across two electrodes.