This project is focused on the development of new peroxides to prepare power cables for High Voltage with increased safety and reliability. These new cables could thus accelerate the development of smart grids that generally refers to a class of technology used to bring utility electricity delivery systems into the 21st century (robustness of the network, more efficiency, …). Power cables for High Voltage are made of a polyethylene cross-linked with alkyl peroxides. During the crosslinking, the peroxide produces by-products that could be volatile and/or polar compounds. The volatiles are responsible for threat regarding explosivity and inflammability of the cable whereas polar species can act as space charge carriers, leading to premature electrical breakdowns. To tackle these issues, the development of new compounds and in particular new peroxides is desired. The first step of this project will consist in the study of both the dissociation mechanism of organic peroxides in experimental conditions close to the cross-linking process combined with the study of the mechanism of the premature electrical breakdowns. Once the specifications for the cables have been determined, the next step is the design, synthesis and characterization of new alkyl peroxides thanks to quantum calculations. The best candidate will be used to prepare model power cables.

The increasing electrification of different systems on an aircraft is an irreversible trend that will move faster and intensify in the coming future. More electrification is expected to happen in the future with a complete elimination of the hydraulic system and possibly with addition of electric and distributed propulsion systems. However, technological hurdles exist for power generation, distribution, and conversion systems in the high power and high voltage ranges with the necessary efficiency and power density required for a transport-class aircraft. Combined with the lower atmospheric pressure, frequent temperature variations, vibrations, and fluid contamination risks, and increased electrical power faults such as partial discharge, parallel/series arc faults, and others can be even more dangerous in an aircraft and cause catastrophic vehicle damage and safery risks for operators in installation and maintenance operations. Optimizing the weight of EWIS without compromising the safety and reliability of the aircraft operation is the main challenge. The project SEWIS (Safe Electrical Wiring and Interconnection System) aims at developing innovative high voltage EWIS components cable and connectors with embedded safety and health monitoring features. Thanks to reactive local fiber optics and electrical sensors distributed inside the cable and the connectors, detecting local electrical faults and ageing of insulation, the safety and reliability of EWIS will be satisfied. SEWIS enables customisation of high voltage EWIS at far greater levels than anyone in this industry has achieved before. SEWIS paves the way to future high voltage European standards of the electrical distribution system.

To maintain its competitiveness, cable and wire industries have to continuously improve their products regarding mechanical, fire, electrical and aging properties while meeting sustainable and environmental requirements requested by the European Union. Moreover, the full implementation of the Construction Product Regulation (CPR) requires the cable companies to use new national safety levels called Euroclasses. This major change brings a unique opportunity to increase the safety level of cables in building, especially in Europe for a market size representing 1 billion €. The current materials used as sheaths for cables are based on polymer blends either with high contents of metal hydrates (>60wt%) or with intumescent systems based on ammonium polyphosphate (APP). The former dramatically decreases the mechanical performances of the wires whereas the latter is very instable toward water. In HAREDY project it is proposed to develop a controlled release flame retardant system based on linear low density polyethylene/ethylene-vinyl acetate copolymer (LLDPE/EVA) blends dedicated to the cable industry. This innovative system is based on both the encapsulation of flame retardant (FR) molecules into halloysite nanotubes (HNT) and on the control of final morphology of the LLDPE/EVA/HNT system regarding fire performances. Through this method it is possible to decrease the aging of the cable and decrease the amount of mineral filler, leading to an improvement of the mechanical properties of the cable. We propose to take benefit from the versatile character of HNT that is an inexpensive, non-toxic and naturally available resource to improve the final performances of the cables. Indeed, FR molecules (such as phosphorus molecules, triazines, pentaerythritol) will be encapsulated into the lumen to improve the HNT fireproofing propensity and to delay the aging toward water. In parallel, inner alumina and outer silica surfaces will be functionalized to control the charring process at the nanoscale and to improve the dispersion of the nanotubes in the blend, respectively. The chemical modification of HNT surfaces will also be targeted to selectively disperse the HNTs either in the EVA phase or in the LLDPE matrix or at the interface between PE and EVA to improve fire performances. LLDPE/EVA/HNT materials will be processed by twin screw extrusion and co-kneader. Processing parameters will be optimized to achieve the targeted selective dispersions. Dedicated characterization based on mechanical, aging and fire properties will be performed so as to identify the relevant treatment routes and proper localization of modified HNT, to select the most promising blend system. The selected materials will then be used to produce cables at an industrial scale. Electrical, fire and aging properties of the insulation material on one side and the definition of the design, the prototyping and the flame and fire performances of the related wire and cables systems according to the standards requested by the electric industry on the other side will be carried out. The consortium is based on three partners: two complementary academic partners (ARMINES/C2MA and UMR5223/IMP) and one industrial company that designs and supplies cables (NEXANS). ARMINES/C2MA is an expert in fireproofing polymer materials and chemical modification of mineral fillers, while UMR5223/IMP is internationally recognized for its expertise in macromolecular engineering, organic-inorganic hybrid materials, rheology and reactive processing of thermoplastic polymers. Additionally, NEXANS is a top-ranking globally cable and wire industry that improve its competitiveness thanks to the development of new products in its R&D center in Lyon. The recruitment of one Ph.D student (36 months in UMR5223/IMP) and one post-doc research assistant (18 months in ARMINES/C2MA) is planned for the 42 months project duration. A budget line of 461,5k€ is targeted.

Current research and development is focusing on propulsive energy components for hybrid aircraft. This will open the path to an all-electrical aircraft. Power levels are predicted to be between 2 and 4MVA for hybrid systems and up to 40MVA for all electrical systems. This will require the transmission of electrical power across the airframe at previously unseen scales. This will not be possible without the development of power dense and safe cabling systems that operate at higher levels of voltage and current. To this end, the objective of HIVACS is to bring together a coherent suite of experimentally validated simulation models to permit the design exploration and optimisation of future aerospace cable systems to allow the aeronautical industry to meet the high-power design requirements of future aircraft programs. The project will also provide recommendations for future standardisation to the relevant standard committees and identify key axis for further development. After performing a state-of-the art review, a requirements and Failure Mode Effect and Analysis (FMEA) will be performed on the design and manufacturing processes on a selection of designs. A range of existing models will be used to assess the performance of these designs with these being adapted to the aerospace environment. The models will be validated by comparison to experimental test bench activities undertaken on existing cables. Once the models are qualified and accepted by NEXANS as being appropriate for adoption in an industrial setting, they will be used in a design optimisation process to determine optimal geometry and sizing of the candidate cables and predict their expected performance. With an optimum cable design, two cable types will be produced using different manufacturing techniques. Both will be tested and qualified. The project will draw upon existing test bench facilities and also develop a specific thermal test bench for thermal cycling ageing.