Electrical treeing

It is a damaging process due to partial discharges and progresses through the stressed dielectric insulation, in a path resembling the branches of a tree.

Ultraviolet light and ozone from these partial discharges (PD) then react with the nearby dielectric, decomposing and further degrading its insulating capability.

These defects further weaken the dielectric strength of the material, enhance the electrical stress, and accelerate the PD process.

The plume is known to consist of a dense network of extremely small water-filled channels which are defined by the native crystalline structure of the polymer.

Electrical trees also originate where bulk or surface stress enhancements initiate dielectric breakdown in a small region of the insulation.

Further tree growth then occurs through as additional small electrical breakdown events (called partial discharges).

An experienced high-voltage engineer can see from the direction and the type of trees and their branches where the primary cause of the breakdown was situated and possibly find the cause.

Modern PD-detection systems employ digital signal processing software for analysis and display of measurement results.

An analysis of the PD signals collected during the measurement with the proper equipment can allow for the vast majority of location of insulation defects.