Insulation Performance Test Research Articles

Simulation test platform for the controlled storage and transfer of liquid hydrogen

Clean-energy propulsion machines, including trucks, tractors, ships, and aircraft, for heavy-duty and long-range mobility have moved, by necessity, to onboard liquid hydrogen (LH2). However, the established method of storage and transfer is problematic due to losses and for any duty-cycle of a sporadic or on/off nature. Integral servicing system methodology is needed for both safety and cost effectiveness in the key drivers of time savings, product savings, and venting exposures. Modern controlled storage technology enables quick and effective vehicle servicing at the point of use. Simulations of controlled storage/transfer (CS/T) methodologies are performed using a multi-purpose LH2 simulation test platform comprised of two primary systems: Cryostat CS900 tank and transfer system and the LS20 liquefaction/refrigeration and storage system. Testing includes both steady-state and transient modes of operation to demonstrate both zero boiloff (ZBO) and zero-loss transfer (ZLT) modes. Technical areas of use include product development for tanks, refrigeration, transfer systems (lines, dispensers, pumps, valves); experimental validation of analytical models and thermofluidic properties; thermal insulation performance test data under relevant conditions; thermophysical characterization of materials and structures; instrumentation and sensors development; tank boiloff and heat flux engineering design data. Descriptions and preliminary test results are given along with thermal performance analyses from real-world testing and experimentation.

High porosity and low thermal conductivity lanthanum zirconate porous ceramics via replica method

ABSTRACT Low thermal conductivity and excellent high-temperature stability make lanthanum zirconate (La2Zr2O7, LZO) a very promising material for high-temperature insulation applications. In this study, LZO porous ceramics with ultra-high porosity and an open-pore structure were prepared by the replica method using a polyurethane template. The flowability and coating quality of the ceramic slurry were optimized. When the dispersant content of the slurry was 0.6 wt% and the alcohol to water ratio was 1:1, the slurry had low surface tension and low viscosity, leading to good coating quality of the ceramic slurry on the sponge template. The pore size between hollow skeletons was 100–500 μm with the hollow structure of the skeletons forming secondary pores. LZO porous ceramics showed high porosity of 87.6%-96.0%, low thermal conductivity of 0.048–0.126 W/(m·K), and compressive strength of 0.13–0.74 MPa by adjusting the ceramic content. A high temperature insulation performance test showed that the temperature difference between the cold side and the hot side of the sample was over 1000°C, indicating the excellent thermal insulation properties of LZO porous ceramics. LZO porous ceramics had good high-temperature stability without sintering shrinkage at heat treatment temperatures below 1500°C.

Influence of different test methods on the accuracy of high current busbar insulation resistance

Compared with the traditional cable, the high current busbar fully embodies its superiority in the process of current transmission, and thus its insulation performance test is of great significance to the safe operation of the line. In this paper, the insulation resistance of the high current busbar is measured by the basic test principle and the voltage injection test method respectively, and then the accuracy and precision of the two test methods are compared. The test results show that the relative error of insulation resistance of positive and negative busbar fluctuates in the range of 0.35%-4.20% and 0.10%-3.33%, respectively, while that of voltage injection test fluctuates in the range of 0.60%-2.80% and 1.10%-1.80%, respectively. Regardless of the basic test principle or voltage injection test, the relative error of insulation resistance in the high current busbar is less than 5%, and the voltage injection test method is more accurate. Compared with the basic test principle, the maximum relative error of Rn and Rp is reduced by 0.87% and 1.00% respectively.

Fabrication of thermal insulation sodium alginate/SiO2 composite aerogel with superior radiative cooling function for firefighting clothing

Purpose This study aims to evaluate the thermal performance of sodium alginate (SA) aerogel attached to nano SiO2 and its radiative cooling effect on firefighting clothing without environmental pollution. Design/methodology/approach SA/SiO2 aerogel with refractory heat insulation and enhanced radiative cooling performance was fabricated by freeze-drying method, which can be used in firefighting clothing. The microstructure, chemical composition, thermal stability, and thermal emissivity were analyzed using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analyzer and infrared emissivity measurement instrument. The radiative cooling effect of aerogel was studied using thermal infrared imager and thermocouple. Findings When the addition of SiO2 is 25% of SA, the prepared aerogel has excellent heat insulation and a high radiative cooling effect. Under a clear sky, the temperature of SA/SiO2 aerogel is 9.4°C lower than that of pure SA aerogel and 22.1°C lower than that of the simulated environment. In addition, aerogel has more exceptional heat insulation effect than other common fabrics in the heat insulation performance test. Research limitations/implications SA/SiO2 aerogel has passive radiative cooling function, which can efficaciously economize global energy, and it is paramount to environment-friendly cooling. Practical implications This method could pave the way for high-performance cooling materials designed for firefighting clothing to keep maintain the wearing comfort of firefighters. Originality/value SA/SiO2 aerogel used in firefighting clothing can release heat to the low-temperature outer space in the form of thermal radiation to achieve its own cooling purpose, without additional energy supply. Graphical abstract

Flexible fabrication of a novel SiO2/AF/ZIF-L composite embedded with MOF structure and its thermal insulation properties

ZIF-L, a metal-organic framework (MOF) material, has a two-dimensional (2D) foliation, a large specific surface area, excellent thermal stability and CO2 adsorption performance, respectively. In this work, in order to further improve the thermal insulation performance of SiO2 aerogel composite fabrics, ZIF-L powder was first prepared as a reinforcing particle, and then added to silica aerogel. Finally, SiO2/AF/ZIF-L composites were obtained by solution impregnation method. The influence of different ZIF-L concentrations on the insulation performance of composites and their influencing factors were studied. Furthermore, these composites were fully characterized using BET measurement, Instron 5967, precision transient thermal performance tester, infrared thermal imager, insulation performance test, thermogravimetric analyzer, and dynamic thermomechanical analyzer. The results showed that 0.12% SiO2/AF/ZIF-L composites had excellent thermal insulation performance, with a thermal conductivity as low as 0.029 W/(m·K). In addition, SiO2/AF/ZIF-L composites fabricated by atmospheric drying method had the best thermal insulation performance under the conditions of gel time of 24 h, hydrolysis time of 5 h, and polycondensation pH value of 5–6.

Synthesis and characterization of a high near infrared reflectance yellow pigment SbxWO3 (x ≤ 0.14)

In this work, a novel yellow near-infrared (NIR) reflective pigment based on the formula of SbxWO3 was developed by high temperature solid-state method at 700–900 °C. The formation of SbxWO3 was confirmed by XRD analysis, and the synthesized pigments are orthorhombic phase with high near infrared reflectivity (84.69%–87.28%). The acid/alkali resistance studies reveal that the color difference ΔE * of the pigments before and after soaking was less than 5, and the as prepared pigments are chemically stable under the atrocious weather. In addition, the synthetic pigments are bright yellowish green (L* = 92.1–92.9, a* = -4.9–4.1, b* = 35.0–37.0). In the heat insulation performance test, the indoor temperature with the SbxWO3 heat insulation coating is 3.1 °C lower than that without heat insulation coating. In summary, the as prepared SbxWO3 pigment has the advantages of high solar reflectivity and less toxic elements, making this new environmentally friendly energy-saving yellow pigment used as a colorant for building exterior coating formulations to reduce heat accumulation and cooling energy consumption.

Structure Design and Performance Analysis of Insulator Replacement Device Based on Live Working in A Distribution Network

In order to solve the problems of high risk and low automation of manual insulator replacement, a live working insulator replacement device is developed. Firstly, according to the shape parameters of insulators, the mechanical structure is composed of a positioning mechanism, a limiting mechanism, a clamping mechanism, and a driving mechanism. Secondly, the control system of the device is designed, and the mechanism is controlled by wireless remote control. Thirdly, the static simulation analysis of the clamping mechanism is carried out by using the finite element analysis software ANSYS Workbench. The simulation results show that the maximum elastic deformation is 0.14366mm, the stress distribution is relatively uniform, and the strain is small, meeting the structural design requirements. Finally, the motion control function test and insulation performance test of the device are carried out. The results show that the designed device has good insulation performance. It meets the needs of daily maintenance and emergency repair of distribution networks below 10kV and has high promotion and application value.

Experimental study on a pilot-scale medium-temperature latent heat storage system with various fins

In this article, a pilot-scale latent heat storage system loaded with 5674.7 kg medium-temperature phase change material (PCM), having four groups of tubes embedded with various fins (longitudinal, H-shaped, spiral, and without fins), was designed and built. During the charging process, the smooth tube had the highest outlet temperature, followed by the tubes with longitudinal, H-shaped, and spiral fins, indicating that the spiral fins had the best heat transfer performance while the smooth's was the worst. The temperature difference in the vertical direction of the thermal energy storage unit was more significant than that in the horizontal direction. Besides, the thermal insulation performance test indicated that the temperature of PCM in the upper part decreased more slowly than that in the lower part due to the charging of the latent heat system being conducted from top to down. Moreover, after charging for 6.5 h, the accumulative energy and the mean power of the tubes with longitudinal, H-shaped, spiral, and without fins were 500.67, 541.57, 567.35, 432.56 MJ, 21.39, 23.14, 24.24, and 18.48 kW, respectively. The calculated charging efficiency of the latent heat storage system was 66.48%.

Effect of liquid diffusion and segregation on GFRP insulation performance in typical hygrothermal environment

Glass fiber reinforced polymer (GFRP) insulation materials widely used in the field of the high voltage transmission will suffer serious performance degradation in hygrothermal environment. In this paper, the effect of liquid diffusion on GFRP insulation performance in three typical hygrothermal environments is studied by experiments and molecular dynamics (MD) simulation. The insulation performance test results show that the insulation properties of GFRP will seriously deteriorate in different hygrothermal environments, and the deterioration of samples in salt spray and acid rain presents significant phase variation. The “segregation” effect of solute particles in salt spray and acid rain is revealed by MD simulation and micro-characterization. Sodium chloride tends to diffuse and accumulate at the interface, resulting in fiber peeling and multi-stage decline in insulation properties. Acid rain is easy to corrode the epoxy resin (EP), and the deep trap introduced by the reaction will inhibit the development of discharge, leading to a quasi-periodic fluctuation degradation in the insulation performance. In addition, there is a competitive effect between solute particles and water molecules, which will prevent the diffusion of moisture. The research provides a basis for revealing the deterioration mechanism of GFRP insulation in different hygrothermal environments. It also has reference significance for the targeted modification of GFRP against hydrothermal aging.

Self-assembly of zinc hydroxystannate on polyethyleneimine supported boron nitride to improve the flame protection properties of waterborne epoxy coatings

Herein, polyethyleneimine (PEI) was loaded on the surface of BN nanosheets to impart them a positive charge. Then, negatively charged zinc hydroxystannate (ZHS) nanoparticles were adsorbed on the surface of BN/PEI composites through electrostatic self-assembly to obtain a novel BN/PEI@ZHS nanoadditive (BP@ZHS). The contribution of BP@ZHS hybrids to the flame retardant properties of epoxy coatings (EP) was characterized by fire performance tests. The thermal insulation performance test results showed that the backside temperature of the BP@ZHS based epoxy (BP@ZHS/EP) fireproof coating remained the lowest value (172.1 ℃) after 60 min of burning. The BP@ZHS/EP sample exhibited the most excellent expansion characteristics (expansion height is 21.5 mm, expansion rate is 16.54) after calcination in a muffle furnace. The TGA experiments illustrated that BP@ZHS/EP had the largest amount (30.8%) of carbon residue due to its catalytic carbonization. Moreover, the smoke density rating (SDR, 46.8%) of BP@ZHS/EP was significantly lower than other samples due to the synergistic effect of BN and ZHS. The carbon residue analysis showed that zinc stannate and BN remained in the carbon framework, thereby improving the strength and thermal insulation effect of the char layer. The excellent fire resistance of BP@ZHS/EP can be mainly attributed to the high barrier effect of BN nanosheets and the multifunctional flame retardant effect of ZHS.

Analysis and detection of fault for substation GIS insulating part based on integrated automation system data

Insulators are important components in gas-insulated metal-enclosed switchgear (GIS), and their safe operation is of great engineering significance. In an air leakage fault accident caused by the cracking of the insulating part of the grounding knife switch of 500kV HGIS equipment, the following measures were taken to find out the cause of the failure: disassembly inspection, equipment assembly review, insulation performance test and residual stress analysis during casting and curing. It turned out that the failure was caused by a lack of cache firmware in the production process. The thermal conductivity and thermal expansion coefficient of the central copper conductor and epoxy resin are different. When the two are solidly adhered, the incompletely reacted insulating parts shrink too quickly when the temperature difference is too large. The copper conductor locally produces excessive residual stress to the epoxy resin, which causes the insulation to crack. According to the causes of the fault, suggestions are put forward, such as replacing the central copper conductor with aluminum material, adding secondary pre-curing procedure in the production process, and adding Remote longitudinal Wave probe on the Insulated Basin side to monitor residual stress in real time.

Research on Measurement Principle and Key Measuring Devices of Pressure Change Rate for Electronically Controlled Pneumatic Brake of Commercial Vehicle Based on Poiseuille's Law.

For intelligence brakes in the electronic pneumatic brake system of commercial vehicles, the pressure change rate is used as the key control parameter and evaluation index. This can improve the brake safety, stability, and ride comfort of the vehicle. The real-time detection of the brake pressure change rate for commercial vehicles is the premise for realizing the accurate control of brake pressure change rate. Based on Poiseuille’s law, an efficient measurement method of brake pressure change rate is proposed for commercial vehicles, and a new measuring device with an isothermal container and laminar flow resistance tube as the core components is designed. Through thermal insulation performance tests, flow resistance tests and measurement accuracy tests, combined with simulations, the effects of structural parameters and copper wire filling density on the performance of the isothermal container are analyzed, and these key parameters are optimized to improve the thermal insulation performance. A tubular laminar flow resistance tube composed of 304 stainless steel capillaries in parallel is designed. The influence mechanism of core parameters such as the number, radius, and length of laminar flow channels on its performance is studied, and the optimal parameter array is selected to optimize its performance. The experimental platform for measuring brake pressure change rate is constructed. By comparing the measurement curve of brake pressure change rate under simulation and experiment, the correctness and effectiveness of the pressure change rate measurement principle and the key components for electronically controlled pneumatic brakes of commercial vehicles are verified to meet engineering requirements.

Study of 160 kV/1 kA R-SFCL Design and Application in Nanao MMC–MTDC Project

The use of a resistive-type superconducting fault current limiter (R-SFCL) in the nanao modular multilevel converter based multiterminal high-voltage direct current transmission project (MMC–MTdc) is the first of its kind over the world. There were no relevant development and operational experience to support the construction of this project. In response to the difficulties in implementation, the corresponding methods were straightened out in this article. These contributions include 1) proposal of an iterative optimization calculation method for the time-varying quenching resistance of the R-SFCL; 2) the establishment of a simulation platform based on PSCAD/EMTDC for MMC–MTdc system with a nonlinear R-SFCL model; 3) two-group with three-outlet-terminal topology scheme for R-SFCL device; 4) dc-side short-current calculation and short-current suppression rate analyses for MMC–MTdc with the developed R-SFCL; and 5) steady-state operation, insulation performance, and power switching tests of the developed R-SFCL. Conclusively, the feasibility of the R-SFCL prototype is verified with the simulation and engineering practice of pole-to-ground test in the nanao MMC–MTdc system. In conclusion, the presentation of these research contents and conclusions illustrates the future value of industrial experience in the design and operation of R-SFCL MMC–MTdc systems.

Transparent EVA film with spectrally selective blocking capacity of ultraviolet and high-energy visible light

ABSTRACT This paper aims to fabricate a type of transparent film to protect human activity and health against ultraviolet (UV) light and high-energy visible (HEV) light. UV326, UV531 and pigment yellow 14 (PY14) were embedded into ethylene-vinyl acetate copolymer (EVA) as UV absorbers and HEV absorbers, respectively. The optical characteristics of EVA blends were primarily explored using Ultraviolet-visible-near-infrared spectrophotometer (UV-Vis-NIR), Luminous transmittance and Haze meter, Fourier transform infrared spectrometer. Meanwhile, the heat insulation performance was tested indoor with a solar simulator and outdoor under actual sunlight irradiation. The results of UV-Vis-NIR revealed the EVA film containing UV326 (0.5 phr) and PY14 (0.01 phr) performed ~100% UV-blocking and HEV light shielding of 42.0%. Simultaneously, this film retained visible light transmission of over 73.9% and performed a ~5 °C decrease compared with pure EVA film in the heat insulation performance test, suggesting a certain heat insulation property without ambient interference.

Research on operation and fault diagnosis technology for EHV/UHV SF6 circuit breakers pre-insertion resistors

Pre-insertion resistors (PIR) are critical components for suppressing the closing inrush current and operating overvoltage during the closing process of the circuit breaker. And it is widely adopted in 800kV and above transmission lines and alternating current filters of converter substations. These special application environments lead to higher failure rates than other electrical components. However, in the daily operation and fault diagnosis of PIR, there is no systematic method to analyze whether there are defects in PIR and the cause of failure after the PIR fails. Based on two PIR failure in series and parallel structures, this paper proposes methods such as dynamic resistance fitting, acoustic and vibration signal detection, insulation performance test, and heat capacity test during operation. In the aspect of fault diagnosis, methods such as PIR splicing based on Iterative Closest Point , stress analysis, and electric field simulation are proposed. Finally, proposed methods can be adjusted to estimate the operating state of PIR through the disassembly inspection to avoid the GIS breakdown accident during the operation of the circuit breaker.

Improving the insulating performance of epoxy resin in humid environments byHTPDMSmodification

AbstractThe rapid development of the electronic packaging industry imposes stringent requirements on epoxy resin insulation materials for lower water absorption and higher insulation properties. Here, hydroxy‐terminated polydimethylsiloxane (HTPDMS) was grafted on the molecular chain of the epoxy resin for enhanced waterproof and insulating properties of the epoxy resin. The HTPDMS‐modified epoxy resin specimens were prepared and subjected to water absorption and water absorption insulation performance tests. The experimental results indicated that the water absorption rate of the modified epoxy resin was reduced by 34.2%, resulting in a 25.2% reduction of the dielectric loss, an 11.6% increase of the breakdown strength, and a 98.3% increase of the volume resistivity. The satisfactory performance of the HTPDMS‐modified epoxy resin insulation material is attributed to the low surface energy and flexible SiO bond of the introduced HTPDMS. Simultaneously, the reduction of surface defects is also conducive to the epoxy resin insulation performance. Thus, HTPDMS‐modified epoxy resin insulation materials can maintain excellent insulation properties in humid environments, making them a promising application in the field of electronic packaging.

Measurement and identification of temperature-dependent thermal conductivity for thermal insulation materials under large temperature difference

Thermal insulation materials are widely used in the fields of thermal protection and the energy conservation at high temperature. Thermal conductivity is one of the most important parameters of characterizing the thermal insulation performance of thermal protection materials. Steady state method such as the guarded hot plate method is normally considered as the most accurate method to measure the thermal conductivity of thermal insulation materials, but the temperature range is limited to below 1000 K. Unsteady state method can be employed at higher temperature but the accuracy is lacking of validation. Consequently, thermal verification experiments are usually conducted by heating the front surface of thermal insulation materials to a very high temperature. However, it is difficult to obtain the temperature-dependent thermal conductivity by using the thermal insulation performance measured with a large temperature difference across the material. In this study, a sandwich structure experimental system is built to carry out the thermal insulation performance tests with a large temperature difference at both steady state and transient state. Both uniform temperature layer method and polynomial fitting method are adopted to extract the temperature-dependent thermal conductivity from the large temperature difference test at steady state. A new transient state identification method is proposed based on the niche genetic algorithm to identify the relation between thermal conductivity and temperature from the transient thermal response. The temperature-dependent thermal conductivity of four thermal protection materials are finally obtained. The identification results prove that the proposed transient identification method is reliable and robust.

A Study on the Sound Insulation Performance of Cross-laminated Timber.

Cross-laminated Timber (CLT) has become an emerging board material of wood construction that is strong enough to sustain a high-rise building. However, many wooden congregate housing units overseas that utilize CLT have poor sound environments because the low mass of such wood influences sound insulation performance. In this research, we explored the effect of different CLT walls on sound insulation performance and integrated applicable sound insulation simulation tools to simplify the process of designing a CLT wall structure. This research aimed at a double wall and CLT combined with a gypsum board as the research object. The sound insulation performance test was carried out in a laboratory, while the sound insulation performance of the structure was predicted through simulation tools and prediction models and then compared with the measured values to verify the applicability of the simulation tool. The CLT with a double wall and CLT with gypsum board (CLT + GB) achieved of 50 dB. The numerical simulation had better prediction performance than INSUL at the double wall, while the double wall with cavity structure was close to the measured result via mass law calculation. The INSUL-predicted CLT with a gypsum board at 500 Hz~3150 Hz was close to the measured value.

Analysis of the Cause of Leakage Oil Defect in a Voltage-Dividing Capacitor of a 500kV Porcelain Circuit Breaker

In recent years, with the development and construction of the power grid system, the porcelain column circuit breaker has been popularized and applied in the 500kV substation. However, in the actual operation and maintenance process, the leakage of oil has been found in the grading capacitor. The disassemble of an oil leakage grading capacitor of a 500kV porcelain column circuit breaker is analyzed in this paper. Through carrying out the sealing test; the insulation performance test; salt spray test and simulation test. At the same time, by comparing the sealing ring and cover plate material; calculating the potential difference of the cover plate and researching electrochemical corrosion factors. We can come to an conclusion that the cause of a suspected the grading capacitor oil leakage is the oil accumulation; and the main reason for the oil leakage problem of the grading capacitor is the electrochemical corrosion phenomenon on the sealing cover plate. Finally, on the basis of the reasons, the relevant rectification measures are put forward.

Effect of steel fiber content on structural and electrical properties of ultra high performance concrete (UHPC) sleepers

This experimental research investigates the structural and electrical responses of ultra-high performance concrete (UHPC) railway sleepers with three different levels of steel fiber content. The UHPC sleepers used in this research were fabricated using a conventional concrete sleeper manufacturing process including the post-tensioning method. They were then evaluated via static bending tests at the rail-seat section and via electrical insulation performance tests. Test results indicate that UHPC sleepers with all three levels of steel fiber content sufficiently meet international requirements. The results from the first cracking load and the load when a crack width becomes 0.05 mm indicate that an amount of steel fiber greater than 1% is required to effectively control early-stage crack development in UHPC sleepers. In addition, the relationship between fiber volume fraction and normalized strength highlights that the material characteristics of UHPC, especially its tensile capacities, correlate strongly with the structural behavior of UHPC sleepers.