The impact of electrical treeing on a cable-embedded fibre

The development of electrical trees near to a cable-embedded fibre is investigated using composite samples with a pin to plane configuration. The tree growth under high electric field is monitored using advanced optical system, equipped with a high-resolution camera and microscope. The slow stressing of polyester material around the fibre surface is assessed as a function of electrical tree development. The tree growth is evaluated by observing the expansion and enlargement of branches in the horizontal and vertical directions. The impact of electrical trees on the fibre optic cables is translated into a distortion of the fibre surface and into irregularities of the surrounding treed area. The shapes and areas of deformed fibre are used as criteria for characterizing cable conditions exposed to high field. A deformation factor is introduced to describe these irregularities in the embedded fibre. Although the focus of the present paper is on the treed region, located between the pin tip and the fibre surface, the conditions of the fibre-to-ground region are also examined.

► In this paper, the impact of tree growth on the integrity of fibre optic cable was investigated with a focus on fibre surface.
► The deformation of the fibre surface was measured and a new concept of Deformation Degree and its limits were introduced.
► Different values of deformation degree ranging from 8% to 22% were determined for different treeing processes.
► The optical fibre should not be exposed to heavy treeing conditions for long periods of time.