The electrical trees initiation at different electric field strength in XLPE cable insulation

In this paper, electrical tree structures once after initiation are presented, and the initiation time of electrical tree at different electric field strength is recorded by the stereomicroscope under continuous voltage. Applied voltage and electrode separation are changed to obtain different field strength. Numerical calculations based on curve fitting show a certain degree of field dependence of the electrical tree initiation time, which leads to a threshold field strength at this experiment system. However, initiation time shows increased dispersion by the decrease of field strength. Even when the field strength is close to the threshold, initiation becomes random. It is inferred that threshold field strength should be considered as an approximate value based on the available experiment results.