Although cross-linked polyethylene (XLPE) has been widely used as a power cable insulation material in electricity infrastructure for decades, it is necessary to find alternatives that exhibit higher performance than XLPE to meet the increasing demand of the industry. To this end, polypropylene (PP) ternary blends that are soft and exhibit high temperature stability were fabricated by melt blending isotactic PP, ethylene-1-octene polyolefin elastomer and ethylene-propylene random copolymer. These blends exhibited improved higher impact resistance at low temperatures (À40 C) and room temperature than pristine iPP. The blends were mechanically stable even when the temperature was increased to ~120 C, unlike XLPE that exhibited rapid degradation of its modulus above ~90 C. Moreover, the soft ternary blends exhibited increased direct current volume resistivity and breakdown strength. Our work realizes the development of high-performance insulators for power cables that can be used over a wide range of temperatures from cold to hot environments.

It is necessary for polymeric materials to have superior tracking resistance against various stress conditions for outdoor applications. In this study, the effect of nano-sized alumina tri-hydrate (ATH) particles on the tracking resistance of silicone rubber (SiR) is studied. Specimens with filler loadings of 1, 3, 5, 10, and 20 wt % are used for performance characterization. From the inclined plane test (IPT) results, apparent improvement in tracking resistance was achieved by mixing 3 wt % of nano-sized fillers, compared to unfilled specimens. ATH/SiR nanocomposites with 5 wt % loading showed comparable tracking performance to SiO2/SiR microcomposites with 20 wt % loading. For detailed analysis, measurements of surface contact angle (SCA) and surface leakage current, and thermo-gravimetric analysis (TGA) were performed. As the nano-ATH filler concentration increased, both thermal stability and leakage current characteristics were improved. Such results agreed with the tracking resistance performance by showing that thermal decomposition and surface charge transport is inhibited in ATH/SiR nanocomposites. Furthermore, performance improvement in nanocomposites was achieved, even at low filler loadings, compared to microcomposites. Meanwhile, the change in SCA was found to be rather limited, regardless of filler loading and filler size.

Due to the increasing use of Electric Vehicles (EVs), the effect of the EV charging power demand on the reliability of the power system infrastructure needs to be addressed. In apartment complexes, which have emerged as a common residential type in metropolitan areas and highly populated districts, high charging demand could result in substantial stress to distribution networks. In this work, the effect of EV charging power demand in an apartment complex on the aging of the Distribution Transformer (DT) is studied. A methodology based on the stochastic characterization of vehicle usage profiles and user charging patterns is developed to obtain realistic EV charging demand profiles. Based on the modeled EV charging profile and the transformer thermal model, the effect of different EV penetration ratios on DT aging for an apartment complex in the Republic of Korea is studied. Results for an EV penetration ratio of up to 30% indicated that DT aging could be accelerated by up to 40%, compared to the case without EV charging. To mitigate this accelerated DT aging caused by EV charging, the effectiveness of two integration approaches of Photovoltaic (PV) sources was studied. Based on a case study that included a realistic PV generation profile, it was demonstrated that a significant contribution to DT reliability could be achieved via the operation of PV sources. A more apparent contribution of PV integration was observed with an energy storage installation at higher EV penetration ratios. At an EV penetration ratio of 30%, a maximum decrease of 41.8% in the loss-of-life probability of the DT was achieved. The effects of different PV integration approaches and power management details on DT aging were also studied. The results demonstrate that the EV charging demand could introduce a significant level of stress to DTs and that this impact can be effectively mitigated by installing PV sources. These observations are expected to contribute toward the effective planning of power system infrastructures that support the design of sustainable cities with the widespread use of EVs.

Despite its versatility, the use of polypropylene (PP) has been limited to subzero temperature applications owing to its inherent brittleness at low temperatures. Herein, we introduce a PP ternary blend toughened by tailoring the domains of ethylene-propylene rubber (EPR) and poly­(ethylene-co-octene) (EOC) within a PP matrix. The PP ternary blend was fabricated by melt-blending a PP and EOC binary mixture; a PP copolymer (PPC) was used as an additive. The Izod impact strength of the PP ternary blends dramatically increased between −50–20 °C compared to that of the iPP/EOC binary blend. Particularly, PP ternary blends with specific compositions exhibited impact strengths above 70 kJ/m2 even at −40 °C. The retraction rate of these blends was similar to that of high-performance specialty rubbers. Moreover, the blends exhibited a low brittleness temperature of −72.9 °C and, hence, may replace the expensive rubber products currently used for various low-temperature applications.

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