Study on the Decrease in Air Dielectric Strength of DC Voltage According to the Ignition Properties of Combustibles

Abstract

Most electrical transmission lines are located in forests, and currently in South Korea, deregulation has allowed various structures to be built on the ground below transmission lines. Events of fires occurring below high-voltage transmission lines can lead to large-scale electrical accidents. To prevent such accidents, this study examined the ignition properties of combustible materials and their relationship with the reduction in air dielectric strength. Experiments were performed on two types of synthetic resins and lumbers, namely cypress and pine. A cone calorimeter was used to measure ignition properties such as effective heat of combustion, heat release rate, and soot yield. In addition, we built a dielectric strength testing device to measure the reduction in air dielectric strength caused by flames. These measurement results can serve as a basis for revising fire safety standards.

Comparisons of enhanced thermal neutron‐ and gamma‐shielding properties in UHMWPE composites containing surface‐treated Sm2O3 and Gd2O3 particles

“…Electrical properties The dielectric strengths for the Sm 2 O 3 /UHMWPE and Gd 2 O 3 / UHMWPE composites with varying filler contents from 0 to 25 wt% are shown in Table5. The results revealed that the dielectric strength tended to decrease with increasing filler contents, with more pronounced reductions found in the Gd 2 O 3 /UHMWPE composites (95% confidence level) because defects and voids at the interfaces between the fillers and the UHMWPE matrix (Figure9) allowed flows of charge (electrical breakdown) to occur at lower voltages as air has much less dielectric strength (approximately 3 kV/mm) than that of UHMWPE 21,47. Notably, the Sm 2 O 3 /UHMWPE composites had higher dielectric strengths than those containing Gd 2 O 3 at the same filler content (95% confidence level), perhaps because the dielectricF I G U R E 8 Mechanical properties (A) tensile strength, (B) elongation at break, and (C) hardness (Shore D) of Sm 2 O 3 /UHMWPE and Gd 2 O 3 / UHMWPE composites with varying filler contents from 0 to 25 wt%.…”