Electrical treeing is a common phenomenon presenting in the insulation of cross-linked polyethylene cables which restricts the long-term safe operation of the cable.With the increasing of operation time

cable failure caused by electrical trees is increasing.In order to explore the initiation and growth dynamics of electrical trees in XLPE

in this paper

firstly

it is verified by the simulation of electrical field that experiments in a piece of XLPE under the needle-plane electrode could be used to research electrical trees instead of in the cable.The measurement system of electrical trees is designed to measure the initial voltage magnitude of electrical trees under the needle-plane electrode with different distance and observe the structural changes of electrical trees in the process of propagation.According to the classification of growth pattern and stages of electrical trees

the growth graph is plotted.The experimental results show that the initial voltage magnitude of electrical trees is less depended on the distance of electrodes.The growth process of electrical trees is categorized as four types

namely

"branch-to-breakdown"

"branchto-pine-to-breakdown"

"branch-to-hybrid of branch and pine"and"branch-to-hybrid of branch and bush".Based on the length of electrical trees

three growth patterns are proposed

being called breakdown pattern

rapid growth pattern and stagnant growth pattern.The latter two patterns are divided into the same four stages.