Insulation Design Research Articles

Issues in the Design and Validation of Coupled Reverberation Roomsfor Testing Acoustic Insulation of Building Partitions

The paper presents the characteristics of the sound field in two pairs of coupled reverberation rooms, designed in accordance with International Organization for Standardization [ISO] (2021c). The analyses are based on the results of the following studies. Firstly, the acoustic airborne sound insulation of selected test samples was measured in the reverberation rooms without using any sound diffusing nor sound absorbing elements. In the second step, the tests were repeated successively with an increasing number of diffusers installed in the rooms. The last stage of the research involved measurements with additional absorbers mounted in the rooms. The results show that although the geometry and construction of the reverberation rooms are in line with the standard guidelines, in most situations it was necessary to use diffusing and absorbing elements to improve the acoustic field in the rooms. Such elements, however, are very undesirable as they significantly limit the usable space of the rooms, making it more difficult to assemble samples and distribute sources and measurement points in the measurement space. Later in the article, the authors prove that even using typically available design tools, i.e., 1st and 2nd Bonello criterions, numerical simulations with the image-source method and the finite element method, or more advanced research methods, such as measurements using scaled samples, it seems impossible to prevent at the design stage the future necessity of using additional diffusing and absorbing elements in the reverberation rooms. Only via verification by measurements performed in the completed rooms provides the assessment if such additional elements are required.

DC allowable electric field strength for naphthenic‐based and paraffin‐based transformer oils

AbstractCurrently, the design of transformers insulation predominantly depends on the allowable alternating current (AC) field values for insulating oil established by Weidmann in the 1980s, lacking the research under direct current (DC) voltage for converter transformers. This study selects naphthenic oils and paraffin‐based oil transformer oil as research subjects, establishing a practical measurement platform to ascertain the oil breakdown characteristics under DC voltage. Furthermore, it statistically analyses the allowable DC field values of the oil. The findings elucidate that (1) the three‐parameter Weibull distribution is more suitable to conduct a statistical analysis for oil breakdown probability, yielding a fitting degree up to 99.95%. (2) for a constant electrode spacing, a 14.81% voltage increment escalates the breakdown probability of the oil gap from 3.33% to 73.33%. Concurrently, an increase in electrode spacing leads to a substantial decrement in the breakdown field strength of transformer oil, with KI25X experiencing a 54.51% reduction as electrode spacing extends from 5 to 25 mm. (3) the constant terms of the allowable DC field strength for S4, KI50X, and KI25X are found to be 19.728, 17.221, and 19.281, respectively. (4) a thorough analysis for differences in physicochemical properties and electrical parameters elucidates the variations in insulation properties across different transformer oils. The findings presented in this study offer essential theoretical and technical foundations for the design, evaluation, and enhancement of insulation structures in converter transformers.

Synergetic Porous Insulating and Passivation Layer Design for High-Efficiency and Stable Perovskite Solar Cells

Synergetic Porous Insulating and Passivation Layer Design for High-Efficiency and Stable Perovskite Solar Cells

Experimental measurement of electric field near the insulator string

This paper explores the electric field distribution near a string of six NJ120 high voltage insulators through experimental measurements under various conditions. Using a distributed capacitance method with custom probes connected to an Arduino-based system, tests were conducted on clean and polluted insulators. Pollution was simulated using a tuf-based solution with conductivities ranging from 0.5 to 1.97 mS/cm. Measurements were taken at 13 heights and four distances (1 to1.75 m) under applied AC voltages of 15 to 80 kV. The study also investigates the effects of damaged insulators, placed at different positions (near the high voltage terminal, in the middle, and near the ground), as well as the role of guard rings in improving field uniformity. Results indicate that pollution and damaged insulators significantly increased field intensity, particularly near the high voltage terminal. Guard rings effectively reduced field peaks, with larger radii and optimal placement providing the best performance. These findings contribute to optimizing high voltage insulator design for enhanced reliability.

Study on the Electric Field Distribution Characteristics of 66 kV Dry-Type Transformer Based on Functional Graded Material (FGM) Treatment

Functional graded materials (FGMs) have been successfully applied for improving the insulation performance of insulators, yet there is currently no relevant literature on their application in dry-type transformers. Therefore, it is meaningful to study the feasibility of using FGMs to improve the insulation performance of dry-type transformers through research on electric field distribution. This paper sets FGMs in the dry-type transformer spacer only or both the spacer and winding end to change the relative permittivity values in the corresponding areas. By comparing the electric field distribution characteristics on the inner and outer surfaces of the high-voltage coil and the lower surface of the spacer of the dry-type transformer under each control method with the case without setting FGMs, the study found that when FGMs were only set on the spacer, the control methods set in this paper could not improve the electric field distribution of the transformer. When FGMs are employed at the spacers and end windings, two modulation strategies can mitigate the electric field intensity on the outer surface of the high-voltage windings. Specifically, a continuous increase in relative permittivity can reduce the electric field intensity by 34.02%, while an initial decrease followed by an increase can result in a reduction of 13.58%. This paper provides theoretical guidance for insulation design of transformers with high voltage levels of 66 kV and above, especially as transformers with high voltage levels face greater challenges in regulating surface electric fields.

Improving the efficiency and reliability of India’s power grid through targeted EHV transmission line investments: a case of UPPCL

This study analyzes the optimization of Extra High Voltage (EHV) transmission line design parameters by Uttar Pradesh Power Corporation Limited (UPPCL) in India to improve power grid efficiency and reliability. UPPCL reduced insulation specifications for 400 kV lines from 27 to 21 disc insulators and decreased live metal clearance from 2600 to 2400 mm, resulting in 7–9% cost savings per line and reduced right-of-way requirements. While initial test lines performed satisfactorily for over 5 years, longer lines experienced operational challenges related to insulator quality, bird activity, and design margins. Tripping issues emerged during adverse weather conditions, particularly in foggy winter periods. Root cause analysis revealed the need for stringent insulator quality control, regular cleaning to mitigate bird dropping contamination, and potential corona ring design improvements. This case study demonstrates how targeted EHV transmission line optimization can yield significant cost and environmental benefits, while highlighting the importance of balancing economic gains with reliability and safety considerations. The findings provide valuable insights for future EHV transmission line designs and upgrades across India’s power grid.

Productivity analysis by insulation design of well with vacuum insulated tubing in SAGD process

This study aims to design insulation and demonstrate its performance on the vertical section of a well in a steam-assisted gravity drainage (SAGD) process. Utilizing the reservoir characteristics of the Athabasca oil sands in Canada, we analyzed oil productivity and derived optimal operating conditions through a multi-objective optimization algorithm. For the simulation, the well's vertical section was insulated with 0.006 W/m‧°C, the thermal conductivity of vacuum insulated tubing (VIT), exhibiting high insulation efficiency. The results indicated that cumulative production increased by up to 20.24%, and production efficiency improved. Additionally, sensitivity analysis using response surface methodology (RSM) revealed that the injection bottom-hole pressure (inj_BHP) was the most significant factor in the insulated well design when parameters varied. A multi-objective optimization using particle swarm optimization (PSO) was conducted to determine the optimal operating conditions, aiming to maximize cumulative oil production and minimize the cumulative steam-oil ratio (cSOR). The optimization resulted in a 39.8% improvement in cumulative oil production and an 88.19% reduction in cSOR, compared to the non-insulation scenario. The findings of this study are anticipated to serve as a guideline for wellbore insulation design in SAGD processes.

Influence of Connecting Cables on Stator Winding Overvoltage Distribution under High-Frequency Pulse Width Modulation

In the variable frequency motor drive system, because the cable impedance does not match the motor impedance, the reflection wave of the voltage wave will be generated. The superposition of reflected voltage waves can lead to overvoltage at the motor ends, which can damage the insulation structure. In this paper, the equivalent circuit models of cable and stator winding are established, respectively. The overvoltage distribution under different power supply frequencies and cable lengths is simulated and analyzed. The influence mechanism of power supply frequency and cable length on the overvoltage distribution of stator winding are studied. The simulation results show that the overvoltage of the first pulse falling edge will be superimposed on the overvoltage of the second pulse rising edge under high-frequency conditions, resulting in a further increase in the overvoltage. The voltage appears in all coils after the middle of the winding. The ground voltage is up to 1.32 times the input voltage, and the inter-turn voltage is up to 9.2 times the average voltage. The increase in cable length will lead to an increase in ground voltage, but the increase in speed will slow down after exceeding the critical length of 300 m. The maximum ground voltage can reach 1.93 times of the input voltage, which is 3.6% different from the calculation result under ideal conditions. The inter-turn voltage changes with the cable length in an N-shaped manner, up to 185 V. The results of this paper are of great significance to further study the insulation design of generator end input.

Design and analysis of acoustic metamaterial sound insulator for noise reduction at multiple frequencies

In this paper, a design of an acoustic metamaterial sound insulator based on porous material with embedded multiple Helmholtz resonators is proposed for noise reduction at multiple frequencies. The periodic unit cell of the metamaterial is made of the porous layer with embedded four, nine, and sixteen different Helmholtz resonators that are arranged in parallel. The cavities of the resonators have the same volume while the parameters of the necks are varied. The sound absorption coefficient and the transmission loss of the metamaterial obtained using finite element method show four, nine and sixteen resonant peaks that correspond respectively to the number of Helmholtz resonators within the unit cell. When the parameters of the necks and the cavities are identical resulting in identical resonators, the transmission loss and the sound absorption coefficient show only one resonant peak. The proposed metamaterial can attenuate the noise at four, nine, and sixteen different frequencies by choosing the number of resonators that constitute the unit cell and adjusting the parameters of the necks. It can be used in many engineering applications such as aerospace for noise attenuation at multiple frequencies.

Impact of barriers on dielectric strength and electric field distribution in point-plane air gap configurations

This study presents a numerical investigation into the dielectric strength of point-plane air gaps, specifically focusing on the influence of dielectric barriers on the potential and electric field distributions under alternating current (AC) voltage. By utilizing two-dimensional (2D) electrostatic simulations through the finite element method (FEM), both configurations—with and without dielectric barriers—are analyzed to assess their impact on vertically arranged point-plane gaps. The study demonstrates that the inclusion of a dielectric barrier plays a crucial role in redistributing the electric field, leading to a more uniform distribution and reducing localized peaks. This results in enhanced dielectric strength, allowing the system to withstand higher voltages without breakdown. The findings are significant for the design and optimization of high-voltage insulators, as incorporating dielectric barriers can improve overall insulation performance and reliability. By improving the electric field distribution, these barriers contribute to reducing the risk of insulation failure, thereby increasing the efficiency and longevity of high-voltage components, making them more reliable for applications in power transmission systems.

Data-driven inverse design of a multiband second-order phononic topological insulator

Second-order phononic topological insulators (SPTIs) have sparked vast interest in manipulating elastic waves, owing to their unique topological corner states with robustness against geometric perturbations. However, it remains a challenge to develop multiband SPTIs that yield multi-frequency corner states using prevailing forward design approaches via trial and error, and most inverse design approaches substantially rely on time-consuming numerical solvers to evaluate band structures of phononic crystals (PnCs), showing low efficiency particularly when applied to different optimization tasks. In this study, we develop and validate a new inverse design framework, to enable the multiband SPTI by integrating data-driven machine learning (ML) with genetic algorithm (GA). The relationship between shapes of scatterers and frequency bounds of multi-order bandgaps of PnCs is mapped via developing artificial neural networks (ANNs), and a multiband SPTI with multi-frequency topological corner states is cost-effectively designed using the proposed inverse optimization framework. Our results indicate that the data-driven approach can provide a high-efficiency solution for on-demand inverse designs of multiband second-order topological mechanical devices, enabling diverse application prospects including multi-frequency robust amplification and confinement of elastic waves.

Impact of close proximity pulse width modulation switching events on electric machine terminal voltages

AbstractElectric machines form an essential part of a wide range of modern systems. When speed control is required, the use of pulse width modulation‐based inverters is generally the solution of choice. It is also usual to connect the machine to the inverter using a cable. The combination of these three elements produces the potential for voltages which exceed the dc link voltage to occur at the machine terminals. Methods for predicting the terminal voltage exist; however, these methods assume that the pulses applied to the system can be considered as isolated, discrete events. The authors highlight an issue with this assumption. When a switching event occurs, it will cause a voltage disturbance in the unswitched phases of the system due to the mutual coupling between the phases. If a second switching event occurs within a short time of this event the resultant voltage will interact with the previous switching event resulting in a higher terminal voltage than would be the case for an isolated event. This effect can be problematic for insulation design if it is not considered. This issue is demonstrated, with the worst‐case scenarios identified and potential methods of reducing terminal voltage being proposed.

Study on recovery and utilization of cold energy for insulation design of liquid hydrogen tanks

Insulation design is one of the key technologies for Liquid Hydrogen (LH2) tanks. To enhance the insulation efficiency and energy utilization of the LH2, this study proposes a novel approach to enhance the insulation performance of LH2 tank and cold energy cascade utilization of LH2. Three Cryo-cooling Insulation Systems (CIS) with various insulation schemes are designed, analyzed and compared from the perspectives of insulation performance, consumption and energy utilization efficiency. An optimal insulation scheme among three CISs is identified and evaluated. Additionally, a dimensionless number (Ψ) is proposed to assess the insulation advantages of the CISs. And the insulation performance and economic feasibility of the system be effectively balanced. The findings reveal that the insulation performance of the proposed CIS outperforms previous insulation methods by a factor of 239.13. Among the schemes in three CISs, Schemes 2 (Position of CSs at 6th, 25th and 35th layers), Schemes 3 (Position of CSs at 10th, 40th and 45th layers), and Schemes 3 (Position of CSs at 3rd, 40th and 45th layers) exhibit superior insulation performance in Cases #1 (CIS of LN2-LAr), Cases #2 (CIS of R14-R170), and Cases #3 (CIS of R1150-R23). Notably, Case #1 achieves the highest insulation performance, showing improvements of 2.58 and 1.63 times over Case #2 and Case #3, respectively. However, the energy output in Case #1 is approximately 248.12 W, constituting 83.10 % and 71.60 % of Case #2 and Case #3, respectively. Case #1 demonstrates the highest specific energy output, with improvements of 30.12 % and 81.05 % compared to Case #2 and Case #3, respectively. In terms of the exergy utilization rate of each equipment, the exergy utilization rate of equipment in Case #1 is the highest among the three cases. The study underscore the feasibility of cold energy utilization for insulation, providing solutions for energy conversion and thermal management of LH2 tanks through cryo-cooling cascade utilization.

A new approach for optimal design of fire insulation coating of steel I-shaped beams and H-shaped columns

A new approach for optimal design of fire insulation coating of steel I-shaped beams and H-shaped columns

Broadband acoustic pseudospin topological states based on the reverse spin-orbit coupling in generalized insulators

Acoustic topological insulators have the excellent characteristic of the pseudospin-dependent one-way transmission of sound edge states immune to backscattering. We realize the broadband acoustic pseudospin topological edge states with subwavelength generalized topological insulators, which is achieved by reverse pseudospin-orbit coupling. The subwavelength band and broadband nontrivial bandgap can be achieved by adjusting the topological structure of the scatterers and introducing resonators. The results demonstrate that the resonator can significantly reduce the frequencies of p-states and d-states by introducing resonance scattering; the scattering size and rotation angles change the frequencies of p-states and d-states in opposite directions by adjusting the distribution of the sound field. Then, we experimentally realize the pseudospin-dependent one-way transmission of sound edge states along the interface separating phononic crystals with distinct topological phases. Our research provides a systematic scheme for the design of acoustic topological insulators with versatile applications.

Thermal analysis and optimization of data center building envelope insulation in different climate zones

The discrepancy in occupancy between ordinary buildings and data centers requires a unique methodology to achieve more effective cooling load reduction. This paper proposes using net heat flow through the building envelope as a control metric, considering the unique requirements of data centers. A corresponding optimization approach is developed to adjust the insulation thickness accordingly. Using the proposed method, five representative cities from different climate zones are analyzed and compared with the current standards. The orientation of roof insulation design for data centers should be contrary to that of ordinary buildings in all five climate zones. In addition to regions with extremely cold and cold climates, the insulation design orientation of the walls surrounding the data center should also be opposite that of ordinary buildings. Lower cooling load is observed at least 50% of time in a year when using the proposed method among climate zones. This article provides an alternative to using natural cooling sources through a building envelope designed specifically for data centers that have greater climate adaptability.

On the Emergence of Shipping Container Homes: Adaptation to Future Climate Projections

Upcycling shipping containers for housing is increasingly recognised as a sustainable solution to housing challenges, particularly in developing economies like Nigeria. This study evaluates the thermal comfort and energy efficiency of shipping container homes under climate conditions projected for 2080. Using meteorological data for Abuja and Lagos under the Representative Concentration Pathway 8.5, a stand-alone shipping container home was simulated. The study incorporated fabric optimisation techniques, using polyurethane foam and polyisocyanurate board insulation, high-performance window glazing, and shading strategies. The findings reveal that without intervention, container homes would experience significant thermal discomfort, with annual discomfort hours exceeding 28°C in both cities. However, with insulation and shading, annual discomfort hours were reduced by up to 87%, and energy consumption decreased by 76%. These results highlight the critical role of insulation and shading in enhancing thermal comfort and reducing energy demand, making container homes a viable solution for sustainable housing in hot climates. The study underscores the need for policy support to promote the integration of advanced insulation and adaptive design strategies to ensure the resilience and sustainability of container homes in future climates.

Investigation of Partial Discharge Transformation Characteristics in Polyimide (PI) Insulations under High-Frequency Electric Stress.

This research delves into the primary issue of polyimide (PI) insulation failures in high-frequency power transformers (HFPTs) by scrutinizing partial discharge development under high-frequency electrical stress. This study employs an experimental approach coupled with a plasma simulation model for a ball-sphere electrode structure. The simulation model integrates the particle transport equation, Poisson equation, and complex chemical reactions to ascertain microscopic parameters, including plasma distribution, electric field, electron density, electron temperature, surface, and space charge distribution. The effect of the voltage polarity and electrical energy on the PD process is also discussed. The contact point plays a pivotal role in triggering partial discharges and culminating in the breakdown of PI insulation. Asymmetry phenomena were found between positive and negative half-cycles by analyzing the PD data stage by stage. A significant number of PDs increased at every stage and the PD amplitude was higher during the negative cycle at the initial stage, but in later stages, the PD amplitude was found to be higher in the positive half-cycle, and scanning electron microscopy (SEM) revealed that the maximum damage occurred near the contact point junction. The simulation results show that the plasma initially accumulates the electron density near the contact point junction. Under the action of the electric field, plasma starts traveling at the PI surface outward from the contact point. Before the PD activity, all parameters have higher values in the plasma head. The microscopic parameters reveal maximum values near the contact point junction, during PD activities where significant damage takes place. These parameter distributions exhibit a decreasing trend over time as when the PD activity ends. The model's predictions are consistent with the experimental data. The paper lays the foundation for future research in polymer insulation design under high-frequency electrical stress.

Adjustable stereo path design method based on pin-sculpture acoustic topological insulator with Z-dislocation defect immunity

The field of topological protected wave engineering, inspired by quantum mechanics, has generated significant interest. Acoustic analogs of electronic topological insulators provide new opportunities for manipulating sound propagation with unconventional acoustic edge modes that are immune to backscattering. Numerous reports have been published on the design of two-dimensional acoustic topological insulators (ATIs). However, the sound path of a two-dimensional design is simple, and its ability to control sound waves is limited. On the other hand, the design of 3D ATIs is relatively complex, making it difficult to manufacture and limiting its versatility. Based on the design idea of the 2D ATIs, inspired by the art named 3D pin-sculpture, an adjustable structure of a finite size consisting of spindle-shaped units with a variable cross section is designed to realize flexible path transformation. Furthermore, unlike two-dimensional structural defects, such as cavities and disorder, the analysis of vertical dislocation defects in finite-sized structures allows for the design of local sound propagation along the z-direction, providing a concept for constructing a stereo path. The designed structure also serves two functions: acoustic switch and delay. This idea offers an alternative approach to designing complex sound transmission paths.

Investigation on Overvoltage Distribution in Stator Windings of Permanent Magnet Synchronous Wind Turbines

The PWM voltage pulses output by the inverter reaches the stator winding of the wind turbine generator through the cable. Due to the impedance mismatch between the motor and the cable, the voltage at the motor end rises under the action of the circuit wave process; on the other hand, electromagnetic oscillation occurs within the motor winding. Higher overvoltage is generated under the combined effect of both, which greatly accelerates the aging and breakdown of the insulation layer of the permanent magnet synchronous wind turbine. In this paper, a three-dimensional electromagnetic model of the permanent magnet synchronous wind turbine generator is established. The distribution circuit parameters of the stator winding of the permanent magnet machine are calculated using the finite element method, and its circuit model is based. The voltage distribution of the stator winding under different PWM excitations is investigated by simulation software, and the effects of the time of the rising edge and the pulse width of the PWM pulse on the stator winding voltage to ground and the turn-to-turn voltage distribution are studied. The results show that the effect of the rising edge time is larger when the rising edge time is shorter, the maximum voltage to ground occurs in the first coil, and the amplitude can be up to 1.5 times of the output voltage. When the rising edge time is longer, the maximum voltage to ground occurs in the end coil, and the amplitude is slightly higher than the output voltage. The trend of turn-to-turn voltage variation is similar for different rising edges; only the maximum turn-to-turn voltage amplitude is different. Pulse width has a small effect on overvoltage and only occurs when the pulse width is less than 10 μs. The research results of this paper are of great significance in revealing the aging and breakdown mechanism of the generator stator insulation, as well as the insulation coordination and design.