Epoxy resin (EP) is a typical and widely used insulating material for medium-frequency transformers (MFTs). The dielectric loss of EP one the key variables in design operation MFT. In this article, six types epoxy/anhydride systems are prepared, MFT calculated by finite element method (FEM) analysis based on broadband spectroscopy measurements. dependence investigated using molecular dynamics simulations over wide temperature frequency range. results show that variation with output power...

Abstract The design of low dielectric-loss epoxy resin (EP) systems plays an important role in the insulation optimization medium-frequency transformers (MFTs). Due to diversity EP and curing agents, traditional method inspired by measurements cannot complete plentiful candidate systems. In this study, molecular dynamics (MD) computation was introduced drive a system for MFTs. By analyzing relationship between dielectric loss motion systems, two MD results were selected as descriptors...

It is generally accepted that the presence of bubbles severely degrades electric strength liquid dielectrics, but influencing factors and mechanisms have yet to be elucidated. Dynamic behavior, partial discharges (PDs) inside bubbles, their effects on breakdown transformer oil are investigated experimentally theoretically in this study. The results show that, under a nonuniform field, does not significantly affect PD inception voltage (PDIV) (BV) liquid, as migrate region with lower field...

The exploration of the genetic resources drought-resistant trees is highly significant for improving ecological environment. Elm are widely distributed in cold and arid regions Northern Hemisphere have a strong tolerance adverse conditions. This study evaluated drought 20 elm varieties (Ulmus pumila L.) collected from areas subject to varying degrees cold. By assessing phenotypic growth indicators, we found that drought-sensitive ULP-2 ULP-3 exhibited reduction height (31 cm 16 cm) root...

Operating experience shows that residual DC voltage remains in GIS bus bar for a long time after opening of disconnectors. This will not only cause accumulation charges and contaminants on the insulator surface, but also easily lead to motion free metallic particles SF6 gas gap, weakening insulation ability GIS. At disconnectors reclosing, impulse could be generated superimpose pre-existing voltage. As result, under combined impulse. paper experimentally studies characteristics lightning It...

Surface charge accumulation on insulators is one of the bottlenecks for development DC electric power system. This paper studies a ±200 kV basin-type insulator designed GIL (Gas-insulated Transmission Line). A surface measurement device made consisting 3-dimension, 4-axes manipulating device, HV shielding conductor installation system and data acquisition new scaling method probe with an inversion algorithm using Cholesky decomposition proposed to obtain density distribution. The dynamic...

The electronic structure of high-quality van der Waals NiPS$_3$ crystals was studied using near-edge x-ray absorption spectroscopy (NEXAFS) and resonant photoelectron (ResPES) in combination with density functional theory (DFT) approach. experimental spectroscopic methods, being element specific, allow to discriminate between atomic contributions the valence conduction band states give direct comparison results DFT calculations. Analysis NEXAFS ResPES data allows identify material as a...

Dielectric analysis (DEA) is an effective method for monitoring the curing process of epoxy resin (EP) in situ, but influence temperature on measurement results limits application DEA with variable temperature. In this study, theoretical basis using glass transition as a bridge and degree by ionic conductivity was analyzed. experiments differential scanning calorimeter (DSC) were carried out mathematical model conductivity, temperature, EP established. The parameters only related to...

Vertical-aligned CdS/g-C₃N₄ heterojunction nanocone arrays have been fabricated on silicon(100) substrates by a plasma sputting reaction deposition and pulsed laser deposition, successively.

It is a challenging work to joint two transparent plastic parts using traditional laser welding because the absorptivity of on short wavelength (800–1000 nm) energy very low. During parts, although absorber and long (1600–2000 can obtain high-strength weld joint, problems unattractive or pollution will occur when used, utilization coefficient about 70% used. To address this issue, paper proposes new production method for absorber-free based reflector assisted method. From three-dimensional...

Even for gas-insulated metal-enclosed switchgear (GIS) equipment that has passed an on-site dielectric test, some failure can occasionally occur without warning. It is necessary to evaluate the effectiveness of tests GIS equipment. In this study, two standard test procedures, power-frequency partial discharge (PD) and lighting impulse (LI) withstand were carried out in a real model platform 550 kV tests. Through experiments, minimum detectable defect sizes determined different curvature...

The presence of free conductive particles in gas-insulated transmission lines (GIL) is the most significant threat to their insulation. non-invasive identification particle defects GILs extremely challenging. Existing methods which use acoustic amplitude-flight time (AAFT) pattern are not often adopted on site due faulty theory, non-robust extraction algorithm, and generally inaccurate calibration. In this study, theory established by L. E. Lundgaard expanded deriving estimation equations...

Under temperature and moisture combined, bubbles will be formed in oil-impregnated paper/pressboard (OIP/OIPB). Although many studies have been done to understand the thermo-induced bubble phenomenon OIPB, formation mechanism is not, let alone its effect on discharge characteristics insulation performance of OIPB. In this article, phenomena mechanisms thermally induced bubbles, their effects partial (PD), breakdown OIPB are investigated. The results show that inception (BIT) decreases...

On-site lightning impulse (LI) test waveform, restricted by the large load capacitance and generator's inherent inductance, has a long wavefront time Tf compared with standard LI, called non-standard LI. The LI been carried out in field. But its insulation defect detecting effectiveness is not clear. In this paper, generating system of impulses different waveform parameters, including double-exponential times range 0.08 ~ 23.5 μs an oscillating around 10 μs, was established. characteristics...

Contamination of free conducting particles is a major threat to gas insulated systems. In HVDC GIL, can be even more harmful due the fact that easily cross gap under DC voltage and distort electric field. systems, impulse overvoltage generated superimposed on operating voltage. As result, GIL will experience this paper, behavior in observed breakdown characteristics particle contaminated voltages are studied. Two motion patterns mainly found: bouncing firefly motions. Particles tend near...

Modifying the volume conductivity of resin impregnated paper (RIP) material is a promising way to eliminate electric field and surface charge along RIP valve-side bushing core surface. In this paper, an electro-thermal coupling model established based on geometry ±200 kV taken from cuts actual core. The influence charge, duration capacitive-resistive transition, tangential are studied. Results indicate that decreasing can help reduce positive On contrary, it increases transition. To meet...