Chemical component analysis of electrical treeing in polyethylene by micro-infrared spectroscopy

Abstract

Conventional infrared spectroscopy is used to investigate the degradation region after electrical treeing in polymers. However, the dimension of the infrared light spot is too large compared with the tree channel, and the position of the light spot is imprecise. Consequently, the micro-infrared spectroscopy is proposed in this paper, which is aim to do chemical analysis for electrical tree area in polyethylene at a micrometer scale. A ramped ac voltage was applied for electrical tree inception in polyethylene, utilizing a wire-plane electrode structure. Slices of samples with electrical trees were then analyzed through micro-infrared spectroscopy. The characteristic group distribution within a selected treeing area was provided through micro-infrared mapping. The experiment results indicated the existence of C=O, C-OH and C-O-C groups, and the content of C-OH and C-O-C groups was more than C=O group. The appearance of C=O group was accompanied with the C-OH group, and the latter absorbance is higher, so it is inferred the C=O group tend to degrade further according to the Norrish type II regime. In addition, not all the electrical tree area had the oxygen containing groups. The material degradation during electrical treeing was discussed with and without oxygen.

Electrical tree degradation in high‐voltage cable insulation: progress and challenges

“… Chemical analysis for the electrical tree (a) Optical micrograph of electrical tree, (b) Micro‐infrared spectroscopic mapping of the red rectangle area in (a) at 805 cm −1 [33]…”

“…The distribution characteristic of C-O-C groups (805 cm −1 ) within a selected electrical tree area is provided through micro-infrared spectroscopic mapping as shown in Fig. 3 [33].…”

Effect of Doping Microcapsules on Typical Electrical Performances of Self-Healing Polyethylene Insulating Composite

“…In the electric field, contaminants (impurities) and defective structures (such as protrusions and voids) in polyethylene cables can distort the electric field, resulting in electrical damage, such as PD and electrical tree. Electric tree is a degradation process, which can cause irreversible structural damage of microns and above, and directly threaten the insulation strength of polyethylene [41,42]. Therefore, the self-healing of electrical tree can greatly improve the insulation performance and service life of polyethylene, but there are still few reports about it.…”

Chemical Analysis of Solid Insulation Degradation using the AFM-IR Technique

“…Associated studies have been largely limited to low oxygen environments [7] where aging is more pronounced. It has also been identified that degradation occurs within and around tree channels during their growth [8], however, the chemical pathways involved are again not yet known, limiting the understanding of the physical processes. An improved understanding of such process would inform the development of methods and materials to increase insulation resistance to aging and extend asset reliability.…”

“…These techniques have limited resolution of around 10 µm, due to the diffraction limit of IR light. Similarly Hu et al used microinfrared spectroscopy in the chemical study of tree channels [8]. Further methods have been used in the study of treeing and tracking, such as Electron Spin Resonance (ESR) and X-ray Photon Spectroscopy (XPS) [10].…”