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) .

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Since the first umbilicals were developed and installed to control and preserve subsea equipment they have continued to evolve to ensure effective operation in an increasingly challenging subsea environment. New material technologies, complex analysis tools and umbilical designs, such as in , have been developed to ensure umbilical systems operate through-out their service life irrespective of the ambient temperature, fatigue loading, hyperbaric pressure and tensile loads applied. Typical Control and Chemical Injection Umbilical Arangement   The subsea industry needs to adapt to the challenge of reducing capital expenditure (CAPEX) costs due to reduced oil price. The potential cost savings could be realised through adapting the subsea processing system to treat processed fluids on the seabed together with utilising longer step out systems from existing facilities. This could drive a new step in umbilical evolution. To support the potential evolution of subsea processing systems, the conventional control umbilical must evolve to incorporate the supply of electrical power and potentially electrical control to replace hydraulic control over long step out distances. This has a significant influence on the design of the umbilical system, introducing several new challenges which need to be addressed through material selection and advanced analysis techniques. This paper will provide an overview of the potential evolution of the Next Generation All Electric umbilical and outline the design challenges and methods developed to maximise the reliability of the umbilical system.

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Since the first umbilicals were developed and installed to control and preserve subsea equipment they have continued to evolve to ensure effective operation in an increasingly challenging subsea environment. New material technologies, complex analysis tools and umbilical architectures have been developed to ensure umbilical systems operate through-out their service life irrespective of the ambient temperature, fatigue loading, hyperbaric pressure and tensile loads applied. In more recent years, as the subsea industry adapts to the challenge of reducing CAPEX costs driven by reduced oil prices, the potential cost savings through adapting the subsea processing system to treat processed fluids on the seabed and / or utilising longer step out systems from existing facilities is driving a new step in umbilical evolution. To support the potential evolution in subsea processing systems, the conventional control umbilical must evolve to incorporate the supply of electrical power and potentially electrical control to replace hydraulic control over long step out distances. This has a significant influence on the design of the umbilical system, introducing several new challenges which need to be addressed through material selection and advanced analysis techniques. This paper will provide an overview of the potential evolution of the Next Generation All Electric umbilical and outline the design challenges and methods developed to maximise the reliability of the umbilical system.