XLPE – layered silicate nanocomposites for high voltage insulation applications: dielectric characteristics, treeing behaviour and mechanical properties

IET Generation Trans & Dist

Yan

et al. 2021

This study reviews the failure of high-voltage submarine cables used in offshore power transmission and provides highlights of their failure characteristic, mechanisms, key issues and prospects. High-voltage submarine cables are designed and applied according to the high-voltage alternating current and high-voltage direct current requirements. Inevitably, the fault occurs in HV submarine cables that is different from that of an underground cable. External aggression remains the primary cause of faults, such as fishing and anchors. Most faults continue to occur at a shallow depth (300 m). The optical fiber inside the submarine cables plays a substantial role in the temperature and stress-strain monitoring and diagnosis. However, it is regarded as a weak point for electrical fault. Insulation breakdown is the leading reason for the short fault. The failure mechanism is complicated when associated with marine conditions. Some defects of insulation and extensive voids, water treeing, mechanical stress, partial discharges, overheating, and electrochemical erosion contribute to the insulation breakdown. Several key issues, including anchoring damage, treeing, defects, and thermal-electric ageing, are proposed. Prospects and new methods related to the cable failure, especially for insulation ageing by treeing and electrothermal effects, are also discussed. INTRODUCTIONSubmarine cables are widely used for new energy power systems in marine environments, such as offshore wind, wave, and solar power transmission applications, and as a power supply to remote areas [1-2]. High-voltage alternating current (HVAC) and high-voltage direct current (HVDC) are the main types of power transmissions by submarine cables [1,3]. Currently, submarine cables with long distances and high voltage carry high electric power between countries and offshore installations, such as oil/gas platforms and offshore wind farms [4][5][6]. Three-core submarine cable or three single submarine cables are employed for HVAC transmission. HVAC technology is simple and has high availability, but it lacks power control and requires reactive compensation [3,7]. Besides, it has a limited distance for high power transmission with high effi-This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Section: Key Issues and The Prospect Of Submarine Cable Failure Analysismentioning

confidence: 99%

Section: Electrical and Water Treeing Degradationmentioning

confidence: 99%

Failure of submarine cables used in high‐voltage power transmission: Characteristics, mechanisms, key issues and prospects

IET Generation Trans & Dist

Yan

et al. 2021

“…Kavitha, D. et al. [11] investigated the performance of nano‐reinforced XLPE for high voltage insulation with a particular focus on dielectric characteristics, treeing behaviour and mechanical properties. It was reported that the changes in the properties were correlated to the morphology of the nanocomposites and polymer filler interactions.…”

Section: Introductionmentioning

confidence: 99%

Study on the water‐tree ageing characteristics of polyethylene/organic montmorillonite and crosslinked polyethylene/organic montmorillonite nanocomposites

Yang²,

et al. 2022

High Voltage

The dispersion state of nanoparticles affects the properties of composites, and the crosslinking process of polymers affects the dispersion state of nanoparticles. In order to investigate the effects of crosslinking behaviour on the water-tree ageing characteristics of nanocomposite dielectrics at the molecular level, polyethylene/organic-montmorillonite (PE/organic montmorillonite (OMMT)) and crosslinked polyethylene/organic-montmorillonite (XLPE/OMMT) nanocomposites were prepared by the melt blending method, after which the accelerated water-tree ageing experiments were conducted using a needle electrode. Fourier transform infrared spectroscopy, differential scanning calorimetry, successive self-nucleation annealing and scanning electron microscope (SEM) tests were conducted to characterise the properties of the samples before and after watertree ageing. The results indicate that the initiation probability and the length of water trees in XLPE/OMMT are less than those in PE/OMMT. The carbonyl index in the watertree area of the two nanocomposites increases, indicating that the water-tree ageing is the result of electrochemical degradation. The crystallisability of the water-tree area degrades, decreasing the crystallinity and the lamellar thickness. The growth of water trees destroys molecular chains and crystal structures, which results in local cracks. There are many holes for the water tree growth in the PE/OMMT specimen. However, the crosslinked meshwork not only restricts the movement of macromolecular chains but also increases the stability of the lamellar barrier effect of OMMT. The combination of the two effects significantly improves the water-tree resistance of the XLPE/OMMT nanocomposite.

“…Based on the dielectric polarisation theories, the dielectric response method is widely used for the detection of water trees [7][8][9] and can be divided into the frequency domain method [10][11][12] and the time domain method [13]. Hvidsten et al found that the tangent value of dielectric loss angle of insulating material increased with water tree ageing and showed strong non-linear characteristics [14].…”

Section: Introductionmentioning

confidence: 99%

“…Based on the dielectric polarisation theories, the dielectric response method is widely used for the detection of water trees [7–9] and can be divided into the frequency domain method [10–12] and the time domain method [13]. Hvidsten et al.…”

Section: Introductionmentioning

confidence: 99%

A novel characterization method for water trees based on the transmission characteristics of complementary split ring resonators

Xiao

et al. 2021

High Voltage

In order to achieve rapid and simple non-destructive testing of water trees in materials, a novel water tree characterisation method based on the complementary split ring resonators (CSRR) was proposed. The characteristics of circular CSRR and rectangular CSRR were analysed in high-frequency electromagnetic simulation software. The resonant frequency of CSRR was found to be correlated to the dielectric constant of the materials. In addition, the lumped equivalent circuit parameters of CSRRs were also calculated and simulated. The results of electromagnetic simulations and circuit simulations achieved good consistency. In the experimental part, sensors based on the two kinds of CSRRs were fabricated and were used to detect the water tree defects in low-density polyethylene samples. The experiment results showed that the method of using CSRR sensors to detect water tree is feasible.