Electrical treeing behavior of DC and thermally aged polyethylenes utilizing wire-plane electrode geometries

Abstract

This paper presents electrical treeing behavior in low density polyethylene (LDPE) and cross-linked polyethylene (XLPE) after exposure to thermal and DC electro-thermal ageing. Both the ageing and the treeing tests were performed by means of two different types of test objects with wire-plane electrode geometry. One type of the tested objects contained only wire electrode of 10 µm diameter, whereas in the other type the wire electrode was attached through a semiconducting tab. The ageing was performed at 80°C with and without 10 kV DC voltage of both polarities connected to the wire and lasted up to 800 hours. The AC electrical treeing tests were applied afterwards for detecting changes of material properties after the ageing. The results showed that the electrical tree inception voltage consistently decreased with increasing time of thermal exposure, whereas the applied DC electric stress had a negligible effect on the observed behavior. Similar effects were found in both the tested materials (LDPE and XLPE) though the object type also influenced the results. For the objects with semiconducting tab, a higher level of the scale parameter was registered because of shielding effect of the tab on the electric field strength at the wire electrode. It also yielded less number of trees growing in parallel at the electrode. The dominant effect of thermal stress on the ageing of LDPE was elucidated by using various analytical techniques, like differential scanning calorimetry, infrared spectroscopy, inductively coupled plasma optical emission spectrometry and oxidation induction time, and it is believed to mainly affect antioxidant content in the test objects.

Electrical Treeing Behavior in Polyethylene Filled with Aluminum Oxide Nanoparticles

“…It has been earlier shown that the influence of the voltage polarity was not significant [9]. In this work -10 kV voltage sources was used for the electro-thermal ageing.…”

“…Thereafter, the manufactured objects are degassed at 60 °C in vacuum for 7 days. A typical problem occasionally appearing during the preparation is formation of kinks at the wire electrode, but no particular precautions are needed as the trees growing at them can be censored [8,9]. …”

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

“…The wire-plane electrode was first presented in [10], and the procedure used in this work was similar to that in [11]. The only difference was that a straight tungsten wire was used here instead of an arc one.…”

Electrical tree characteristics of XLPE under repetitive pulse voltage in low temperature

“…Researchers found that electrical tree was the main reason for insulation degradation during partial discharge process [16]. Many experiments were carried out to characterize electrical tree growth behavior in polymers [17][18][19][20][21]. It was found that the treeing process was affected by many factors including voltage, frequency, temperature, space charge, harmonic distortion and crystallization [22][23][24][25][26][27].…”