Inhibition of Rejuvenation Liquid on Trees in XLPE Cables under Switching Impulse Voltages

Abstract

In this paper, the inhibitory effect of preinjected rejuvenation liquid on trees in cross-linked polyethylene (XLPE) cables was investigated. Experimental samples were prepared by inserting needles into XLPE samples, and many equally-spaced holes existed in the outer semiconductive layer. All cable samples were divided into two groups. One sample group was treated with rejuvenation liquid, while the other group was the control group. A tree accelerated aging system was used to obtain trees in the XLPE cable samples. During the aging experiment, an impulse voltage was applied to the samples repeatedly. The micromorphologies of the two groups were observed. Based on the micromorphologies, two parameters were determined: the initiation rate of electrical trees and the average length of trees. Furthermore, the electric field distribution was simulated to analyze the initiation of electrical trees. The results indicate that an electrical tree is much harder to initiate in the pretreated XLPE cables than in the untreated cables. This phenomenon is likely attributed to the dielectrophoretic forces in the pretreated cables. Moreover, rejuvenation liquid deposited in XLPE causes a substantial reduction in the Maxwell stress of molecular chains. Rejuvenation liquid inhibits electrical tree initiation and water tree growth to a great extent.

Effect of nucleating agents on the electrical properties of cross‐linked polyethylene under tensile stress

“…The tensile stress also causes the molecular chains to move along the direction of force, increasing the distance between the molecular chains, increasing the free volume, and the energy transferred by charge transport in the free volume increases. At the same time, the energy barrier between molecular chains decreases, which is conducive to the transport of charges, and the damage of carrier on the molecular chain structure is strengthened [44][45][46]. This easily forms electric field distortion and triggers partial discharge, promoting the degradation of the insulation medium molecular chain, showing an increase in the degradation area of the electric tree and rapid growth of the electric tree.…”

Self-Healing Properties of Water Tree Damage in Multilayered Shell–Core-Structured Microcapsules/Cross-Linked Polyethylene Composites

“…Water tree channels lead to a decrease in the dielectric strength of the material and an increase in the electrical resistance, which in turn causes partial discharges and material damage. Although there have been techniques to repair water dendrite defects in cables by injecting a repair agent that reacts with water, the method requires the line to be de-energized, pressurized, among others, which severely limits the scope of its use in a practical sense [ 6 ]. At the same time, due to the difference between the molecular diffusion rate of the restoration solution and the catalyst, resulting in the initial position being prone to the accumulation of the restoration solution and becoming clogged, the effect of the water tree inside the cable restoration is not as expected [ 7 , 8 ].…”

Electric Field Distribution and Dielectric Losses in XLPE Insulation and Semiconductor Screens of High-Voltage Cables

“…Many articles have described the effect of various factors on the electrical conductivity γ of cross-linked polyethylene [1,[4][5][6][7][9][10][11][12]18,. These factors include electric field stress, percentage of nanoparticles (most commonly Al 2 O 3 ), distance from the high-voltage conductor, temperature, aging time, degassing time, frequency, and insulation thickness.…”

“…of semiconductor screen and pure XLPE used to calculate the electric field distribution and dielectric losses in high-voltage cables[1,[4][5][6][22][23][24].…”