Breakdown Properties of Cables with Different Inorganic, Insulating Nanomaterials

The insulation performance of cable insulating materials can be optimised via matrix modification. Typically, low-density polyethylene (LDPE) is used as the matrix, and a certain proportion of nanoparticles are added to this matrix. To explore the effects of nanoparticles with different forms on the structural interface and crystal morphology of the material, nano-MMT and nano-ZnO were added to LDPE, and comparative experiments were carried out. Based on microscopic test results, material insulation performance changes before and after optimisation were observed. Then, simulation cable models with different insulating materials were developed. Based on the simulated electrical measurements, the thermal breakdown performance of the different insulating materials was tested. According to infrared stereo vision detection results, anomalous temperature points in the cables can be located accurately. Finally, based on macroscopic test results, we verified whether the inorganic, insulating nanomaterials meet the requirements for high-voltage transmission.

Detection and Prediction of Internal-Caused Fire in Tunnel Cable by an Equivalent Transient Thermal Circuit Model

Internal-caused cable fires are one of the most common cable fires, and anomalous temperature increase of the cable core is one of the first signs. However, when a cable is operating with electricity, the temperature of the core conductor cannot be monitored directly; therefore, this characteristic cannot be used in detection and prediction of internal-caused fire in electric cable effectively. An analogous transient thermal circuit model is created, simplified, and optimized to properly compute the temperature of the cable core. Afterward, by using the cable internal-caused fire experimental platform and adjusting current carrying capacity of the tested cable, an experiment is conducted for stimulating the very early stage of three-core cable internal-caused fire. The maximum relative errors of the transient thermal circuit model and the trisection transient thermal circuit model are less than 10% when comparing the experimental data with the calculation results, and the average relative error of the calculated value of trisection transient thermal circuit model is 1.08% after layered optimization. The algorithm model can satisfy the requirement for early detection and prediction in the very early stage of cable internal-caused fire.

Evidence of a coupled electron-phonon liquid in NbGe2

Whereas electron-phonon scattering relaxes the electron’s momentum in metals, a perpetual exchange of momentum between phonons and electrons may conserve total momentum and lead to a coupled electron-phonon liquid. Such a phase of matter could be a platform for observing electron hydrodynamics. Here we present evidence of an electron-phonon liquid in the transition metal ditetrelide, NbGe2, from three different experiments. First, quantum oscillations reveal an enhanced quasiparticle mass, which is unexpected in NbGe2 with weak electron-electron correlations, hence pointing at electron-phonon interactions. Second, resistivity measurements exhibit a discrepancy between the experimental data and standard Fermi liquid calculations. Third, Raman scattering shows anomalous temperature dependences of the phonon linewidths that fit an empirical model based on phonon-electron coupling. We discuss structural factors, such as chiral symmetry, short metallic bonds, and a low-symmetry coordination environment as potential design principles for materials with coupled electron-phonon liquid.