Space Charge Formation In Polyethylene Research Articles

Influence of external electric fields and temperature on the behavior of water and acetophenone molecules in C120H242 chains: A molecular dynamics study

Polymers are widely used as electrical insulating materials, with polyethylene being one of the most commonly used materials. However, the presence of water and acetophenone (AP), which are byproducts of the cross-linking agents used to produce cross-linked polyethylene, can cause space charge formation and electrical degradation. In the present study, the effects of an external electric field and temperature (250–400 K) on the dynamic and structural properties of water molecules (1 wt%) with AP molecules (1 wt%) in C120H242 chains were evaluated by molecular dynamics simulations with the SPC/E water model and the general AMBER force field. The results showed that water molecules diffused into the C120H242 chains under the condition of E = 5 GV/m in the temperature range of 250–400 K. Moreover, the AP molecules diffused into the C120H242 chains under the condition of E = 1 and 5 GV/m in the temperature range of 350–400 K. These results support a previously proposed model for space charge formation in polyethylene, which was based on pulsed electro-acoustic measurements. Thus, we verified a molecular model for the space charge and a suppression mechanism for electrical degradation from the viewpoint of the diffusion of water and AP molecules.

ポリエチレン中の空間電荷分布形成に与える架橋剤分解残渣の影響

ポリエチレン中の空間電荷分布形成に与える架橋剤分解残渣の影響

アセトフェノンがポリエチレンの空間電荷形成に与える影響

アセトフェノンがポリエチレンの空間電荷形成に与える影響

Study of the mechanism of space charge formation in polyethylene

The mechanism of space charge formation in polyethylene is discussed. The space charge distributions in various samples of polyethylene were measured with the pulsed electroacoustic technique (PEA). The moisture content of the polyethylene plays an important role in the formation and transport of space charge caused by injected electrons and holes or ionization of impurities, including by-products of cross-linking agents and catalyst residues. Polymer structures, such as straight chain, branch chain, co-monomer, and crystallinity, also influence space charge formation and transport in various ways.

ポリエチレンの電気伝導と空間電荷形成へ及ぼす微量不純物の影響

ポリエチレンの電気伝導と空間電荷形成へ及ぼす微量不純物の影響

Some factors for the space charge formation in polyethylene

AbstractInformation on space‐charge behavior in thick insulated samples aids in understanding the dc characteristics of polymer‐insulated dc cables. The pulsed electroacoustic method is used to investigate several space charge formation factors in 2 mm‐thick polyethylene (PE). The following results were obtained.For measurement factors:(1) A polymeric semiconducting electrode provides a more accurate measurement than does a metal electrode as a result of better matching of acoustic impedance with PE.(2) Within a dc electrical stress range of several tens kV/mm, the space charge distributions under and after dc voltage application are almost the same; this is due to a comparatively long time of space‐charge decay.(3) The space‐charge distribution of a plate sample agrees with that of a cable sample having the same insulation thickness.For insulating material factors:(1) The amount of space charge in crosslinked polyethylene (XLPE) is much larger than that in low‐density PE (base of XLPE).The space charge of XLPE continues to increase even after dc voltage application (24 h); that of LDPE reaches equilibrium with a few hours.(2) The aforementioned space charge difference between XLPE and LDPE is assumed to be caused by ionic impurities in XLPE, not by the additives themselves (acetophenon and cumylalcohol as byproducts of cross linking and antioxidant).

Interfacial charge in polyethylene/ethylene vinylacetate laminates

Space charge formation in polyethylene (PE)/ethylene vinylacetate copolymer (EVA) laminates has been investigated using a pulsed electroacoustic method. The PE shows heterocharge while the EVA shows a broad distribution of positive charge over the sample. The positive charge in EVA decreases with the increase of vinylacetate (VA) content in EVA. Interfacial charge is found in all laminates and remains unchanged by heat treatment at 100/spl deg/C to 1 h and by coating chemicals such as silicone oil and trimethylolpropane trimethacrylate at the interfaces, This interfacial charge distorts the electric field distribution in the direction of increasing the electric field in the PE layers. The charge distribution in PE/EVA blends has been measured and is explained via the results obtained with the laminates.

ポリエチレンの空間電荷形成に及ぼす因子

ポリエチレンの空間電荷形成に及ぼす因子

DC Treeing Breakdown Associated with Space Charge Formation in Polyethylene

It is well known that space charge accumulation has a great influence on both the short-time and long-time breakdown strengths of plastic insulation systems operating under direct voltages. In this paper, dc treeing phenomena initiated from the tip of a needle electrode inserted into a polyethylene specimen have been investigated under various conions. The characteristics of four kinds of trees, dc tree, short-circuit tree, polarity reversal tree and impulse tree, were investigated as a function of the voltage-rising speed, period of dc prestress, time before the short-circuit or the application of a voltage of reversed polarity, impulse voltage, needle electrode material and temperature, etc. Also, thermally stimed current (TSC), thermoluminescence (TL) and photo-induced current techniques were applied to estimate the nature of the trapped carriers and carrier trapping centers. From the experimental results, it was concluded that a homo-charge is formed at high electric stresses and that the homo-charge induces an electric field distortion around the needle tip. In order to explain the length of the tree as a function of the various factors mentioned above, a model for the space charge formation is proposed, including the process such as charge injection, trapping and its diffusion.

Tree Initiation and Time of Space Charge Formation in Polyethylene

Tree Initiation and Time of Space Charge Formation in Polyethylene

ポリエチレンの空間電荷形成に関連した直流トリーイング破壊の極性効果

ポリエチレンの空間電荷形成に関連した直流トリーイング破壊の極性効果