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Extruded crosslinked polyethylene (XLPE) submarine cables with factory joints play a significant role in cross-sea transmission interconnection projects. Morphological variations in the insulation of submarine cables and factory joints are caused by differences in process parameters. The dielectric properties of XLPE are affected by its morphology. In this study, samples of XLPE insulating materials were taken from the cable bulk, cable-joint transition, and factory joint, respectively, of a 500 kV high-voltage AC submarine cable. The crosslinked morphology was obtained by extraction and infrared spectrometer. The crystal morphology was obtained by the way of etchant, differential scanning calorimetry, and X-ray diffractometry. The Weibull distribution was used to gather statistics of AC breakdown strength. The results show that in comparison with the cable bulk, the contents of crosslinked byproducts are higher in the cable-joint transition and factory joint. At the same time, there is a sparse distribution in terms of crystal morphology, with the appearance of smaller grains and lower crystallinity, in the cable-joint transition and factory joint. These morphological variations would generate more heat during electron transport and lengthen the free paths of electrons, then lead to the occurrence of AC breakdown. The results might provide insights into the optimisation of the morphology of XLPE, in particular submarine cable factory joints. 2 Experimental 2.1 Sample preparation Samples were obtained from the same 500 kV XLPE submarine cable with joint fabricated in factory. The cable bulk was extruded by vertical continuous vulcanisation. The cable-joint transition

Droplet generation in a T-junction with surfactants is simulated using our recently developed lattice Boltzmann method. The method is first used to explore the effect of surfactant concentration [Formula: see text] on droplet generation. As [Formula: see text] increases, droplet generation tends to shift from squeezing to dripping regime and then to jetting regime. In the clean system, the upstream pressure varies almost periodically with time. However, in the surfactant-laden system, the upstream pressure no longer varies periodically but overall increases with time for droplet generation in squeezing and dripping regimes. This is because the addition of surfactants results in an additional pressure drop between the front and rear of the generated droplet. Then, droplet generation in both clean and surfactant-laden systems is compared to explore the surfactant role under different values of the capillary number [Formula: see text]. In either clean or surfactant-laden system, the pressure upstream of the junction rapidly decreases as [Formula: see text] increases. In the presence of surfactants, the upstream pressure overall increases with time for droplet generation in squeezing and dripping regimes, but the increased amplitude decreases with [Formula: see text]. Finally, we establish the phase diagrams describing how the droplet generation regime varies with flow rate ratio and [Formula: see text] in both clean and surfactant-laden systems. It is found that the addition of surfactants reduces the critical capillary number distinguishing squeezing from dripping and the critical capillary number distinguishing dripping from jetting.

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