Insulating MgO–Al₂O₃–LDPE Nanocomposites for Offshore Medium-Voltage DC Cables

Abstract

A polymer−metal oxide nanocomposite is a key in developing a high-temperature insulation material for power electronics and high-voltage direct current (HVDC) and medium-voltage direct current (MVDC) subsea cables having the capability of transmitting offshore renewable energy with lower losses and higher reliability. To achieve a higher operation voltage level and larger power capacity at a reduced cable size, weight, and volume, the lighter material offering improved electrical insulation at a high operating temperature is required. Addition of metal oxide ceramics in the polymer is shown to improve the insulating properties of the polymer used in the cable and power electronic applications; however, their performance deteriorates at elevated temperatures as thermal energy facilitates the electron injection to the bulk material by following conduction according to the Schottky emission. In this work, the heat insulating Al 2 O 3 nanoparticles are added to the MgO−polyethylene nanocomposite to observe the effect of the interface between mix oxide nanoparticles on current density and breakdown strength of the nanocomposite compared to the MgO−polyethylene nanocomposite at room and elevated temperatures (90 °C). The concentrations of the MgO and MgO + Al 2 O 3 mixture were varied from 1 to 12 wt % to find out that the nanocomposite containing MgO showed the best response than MgO + Al 2 O 3 at elevated and room temperatures. There was no unified trend observed in the leakage current density and breakdown strength results for the MgO + Al 2 O 3 nanocomposite, indicating the absence of the interface formation between MgO and Al 2 O 3 . The decrease in the interaction radius, calculated using numerical simulation of the nanoparticle dispersion state, resulted in the high breakdown strength. Addition of 12 wt % MgO helped achieving the highest breakdown strength, but overall breakdown strength for the MgO + Al 2 O 3 nanocomposite improved at elevated temperatures. All nanocomposites showed improved electrical insulating properties compared to virgin low-density polyethylene (Pure LDPE) .

A Review of Sensing Technologies for Non-Destructive Evaluation of Structural Composite Materials

“…The emitted ultrasonic signal travels within the Though FMCW has recently been applied as a stand-alone system for NDE of WT blades for studying the delamination, cracks, and water ingress [35,37], the literature shows that there is a wide area of applications for FMCW-based NDE of composites. Due to its nature of interaction with dielectric materials, it can also be used to identify variable materials present in a composite material [151], and the concept can even be extended for a micron-level nanoparticle agglomeration study, which is a critical aspect in bespoke polymer nanocomposites [152][153][154]. However, similar to other methods, it also has some limitations, which include a limited depth of penetration against other methods involving ground penetrating radar, X-ray, Gamma, and neutron [155], in addition to spatial resolution, which is limited by the bandwidth and low power, which limits the penetration depth in the target composite [18,35,36,155].…”

Optimising Crystallisation during Rapid Prototyping of Fe3O4-PA6 Polymer Nanocomposite Component

“…PMCs with different functionalities or multifunctionalities can be produced using different types of nanoparticles (NPs) (Figure 1); however, the uniform dispersion of NPs is a precondition to achieve the required functionality. Previously, many nanoparticle dispersion techniques, such as melt blending, solution blending, high-shear mixing and in situ polymerisation, have been used [3][4][5][6][7][8]. However, the in situ PMC manufacturing method is most favoured for preparing PA6 PMC, as it provides the ease of mixing the nanoparticles in a low-viscosity ε-caprolactam monomer before the activator/catalyst-mediated polymerisation [9] is carried out, ensuring effective dispersion.…”

“…Due to interface adhesion and MNPs dispersion, the degree of crystallinity and the crystalline structure within the polymer are affected [3,4], which, in turn, affects the multifunctional properties of the synthesised polymer magnetic PMC [1,[10][11][12]. Previously, many nanoparticle dispersion techniques, such as melt blending, solution blending, high-shear mixing and in situ polymerisation, have been used [3][4][5][6][7][8]. However, the in situ PMC manufacturing method is most favoured for preparing PA6 PMC, as it provides the ease of mixing the nanoparticles in a low-viscosity ε-caprolactam monomer before the activator/catalyst-mediated polymerisation [9] is carried out, ensuring effective dispersion.…”

Flexible Low-Density Polyethylene–BaTiO3 Nanoparticle Composites for Monitoring Leakage Current in High-Tension Equipment

“…There are many examples of piezoelectric polymer−NP composites with silane−ethanol 12,13 and oleic acid 14 coatings. Silica coatings using the Stober method 15 can potentially be a cost-effective and scalable process for commercial NP functionalization manufacturing.…”