Conventional Insulation Research Articles

Preserving the Cellular Tissue Structure of Maize Pith Though Dry Fractionation Processes: A Key Point to Use as Insulating Agro-Materials.

Plant biomass has various compositions and structures at different scales (from the component organs to their constitutive tissues) to support its functional properties. Recovering each part of the plant without damaging its structure poses a challenge to preserving its original properties for differential dedicated end uses, and considerably increases its added value. In this work, an original combination of grinding based on shearing stress and separation based on particle size and density was successfully used to sort rind (65% w/w) and pith (35% w/w) from maize stem internodes. More than 97% of the rind was isolated. The pith alveolar structure was well preserved in coarse particles, making them suitable for insulation bio-based composite materials, a promising alternative to conventional nonbiodegradable insulation panels. Boards produced from the dry fractionated pith exhibited thermal conductivities like those produced from hand dissected pith, with values equal to 0.037 W·mK−1 and 0.039 W·mK−1, respectively. In the finest fraction (particle size <1 mm), the pith vascular bundles (around 300–400 µm in diameter) were dissociated from parenchyma cells and successfully isolated using a cutting-edge electrostatic separator. Their structures, which provide the plant structural support, make them potentially valuable for reinforcement in composite materials.

Research and Preparation of Graphene Foam Based on Passive Ultra-Low Energy Consumption Building New Ultra-Thin External Wall Insulation Material

As an advanced upgrade form of green buildings, passive ultra-low energy consumption building is an inevitable trend of future building development. Therefore, it is of great significance to develop new fireretardant and ultra-thin thermal insulation materials for exterior wall. In this paper, we focus on graphene foams with excellent thermal insulation, and the microstructure of graphene hydrogel was studied as an intermediate to prepare graphene foam. The microstructure of graphene hydrogel as an intermediate to prepare graphene foam was studied. This study was proposed based on two problems: (1) Graphene hydrogels change from hydrophilic/lipophobic to hydrophobic/lipophilic after freeze-drying. (2) Compared with the poor mechanical properties of graphene hydrogels, graphene-based nanocomposite hydrogels have highly extensible and resilient properties. We studied the microstructures of both graphene and graphene hydrogel. Notably, many stomatas were distributed in graphene hydrogel, and the proportion could be adjusted by changing the quantity and type of reducing agent. This property can be applied to adjust the microstructure and properties of graphene foams. Based on the practice of passive ultra-low energy consumption buildings, the heat insulation mechanism of graphene foam insulation material and the preparation process of graphene foam were studied through theoretical analysis and experimental research. The results of this study provide a theoretical basis and scientific basis for the development and application of graphene foam insulation materials, and promote the industrial production of graphene foam insulation materials, with important research value and application prospect to solve the problems of high quality and large-scale development of passive ultra-low energy consumption building restricted by conventional exterior wall insulation materials.

Performances Study of Natural and Conventional Building Insulation Materials

Performances Study of Natural and Conventional Building Insulation Materials

Numerical study of the feasibility of coupling vacuum isolation panels with phase change material for enhanced energy-efficient buildings

Effective thermal performance of a building envelope is crucial to reduce total energy consumption in buildings. In the past decades, different insulating materials and techniques have been proposed to improve building energy efficiency. Among various insulating materials vacuum insulation panels (VIPs), due to their extremely low thermal conductivity, become one of the emerging materials, striving for replacing conventional insulation materials. From different perspectives, phase change material (PCM) is another promising material with a large amount of latent heat capacity to improve building thermal inertia. Much research has been conducted for PCMs or VIPs individually. However, there are rare studies found in the literature to integrate both materials in the building envelopes. Therefore, this study aimed to evaluate the feasibility of an energy-saving building wall by coupling VIP with PCM as a compact unit that could significantly reduce heat flux through the wall, thereby leading to a tremendous reduction in energy consumption. The aging effect of VIP is also considered to examine its long-term thermal performance and compared with that of a traditional thermal insulation material-expanded polystyrene (EPS). The results reveal that the combined utilization of VIP and PCM in the same building envelope can reduce the heat flux oscillation through the wall more effectively, as compared to using the individual one. The maximum heat flux oscillation through the wall is found in direct proportion to the amplitude of the input loading, and inverse proportion to the VIP and PCM thickness. In addition to decreasing the heat flux oscillation through the wall, the integration of the PCM layer also causes a time delay on the peak heat fluxes, showing great potential to shift the electricity load from peak to off-peak hours. Results also show that the VIP with extremely low thermal conductivity allows the building envelope to achieve the same thermal performance with up to 77.3% of wall thickness saved compared with EPS. Moreover, the optimal integrating location of PCM is found to be on the interior side of the VIP layer under various loading conditions. The optimal PCM melting temperature of the PCM-VIP-based wall is highly dependent on the input loading conditions in direct proportion.

Multi-tonal low frequency noise control using Helmholtz resonators with complex cavity designs for aircraft cabin noise improvement

The noise control at multiple tonal frequencies simultaneously, in the low frequency range, is a challenge for aerospace, ground transportation and building industries. In the past few decades, various low frequency noise control solutions based on acoustic metamaterial designs have been presented in the literature. These solutions showed promising performance and are considered a better alternative to conventional sound insulation materials. In the present investigation, it was noticed that subdividing the cavity of a Helmholtz resonator allowed the control of multi-tonal noise at several resonance frequencies simultaneously and a shift of the resonance peaks towards the low frequencies. This paper proposes concepts of Helmholtz resonators with subdivided cavities to improve the sound transmission loss (STL) performance and simultaneously control the noise at several tonal frequencies. HRs with cylindrical shaped cavities were embedded in a layer of porous material. The STL of the metamaterial noise insulation configuration was predicted using serial and parallel assemblies of transfer matrices (TMM) incorporating a thermo-viscous-acoustic approach to accurately account for the viscous and thermal losses of acoustic wave propagation within the metamaterial. The STL calculated using the proposed TMM approach were observed to be in excellent agreement with the finite element method (FEM) numerical results.

Environmental Impacts of Renewable Insulation Materials

According to the IEA Global Status Report for Buildings and Construction 2019, one of the main industry sectors causing environmental impacts is the construction sector. Hence, construction materials from renewable resources are expected to have a large potential to decrease these impacts. In this study, a Life Cycle Assessment (LCA) was conducted for four different insulation materials from renewable feedstock: insulation made from pasture grass, seaweed, reed, and recycled jute fibres. Additionally, the effects on land use change were evaluated for pasture grass insulation using the LANCA® methodology. To put the LCA results in relation to those of non-renewable resources, a comparison of standardized LCA values for conventional insulation materials is presented. In general, the renewable insulation materials show fewer environmental impacts than their conventional counterparts. In particular, these materials have advantages regarding greenhouse gas emissions and their impact on climate change. Of the analyzed materials, seaweed showed the overall lowest emissions. It can be concluded that insulation materials from non-mineral, non-fossil, and non-wooden resources are still fairly niche in terms of market share, but they have extraordinary potential in decreasing the environmental impacts of construction ventures.

Effect of Forced-Air Warming Blanket on Perioperative Hypothermia in Elderly Patients Undergoing Laparoscopic Radical Resection of Colorectal Cancer.

The study aimed to evaluate the effect of forced-air warming blanket combined with conventional thermal insulation measures on inadvertent perioperative hypothermia (IPH) in elderly patients undergoing laparoscopic radical resection of colorectal cancer. A total of 70 elderly patients undergoing laparoscopic radical resection of colorectal cancer with general anesthesia were included, and divided into conventional warming treatment (CT) group or forced-air warming treatment (FT) group. In the FT group, based on the conventional warming strategy, patients received prewarming with the forced-air warming blanket (38°C) for ≥20 minutes before induction of anesthesia, and received this treatment continuously during operation. The core body temperature, recovery time from anesthesia, extubating time, and length of stay in the postanesthesia care unit were recorded. The incidence of IPH and postoperative shivering was observed. The incidence of IPH was significantly lower, and average minimum body temperature during the operation was significantly higher in the FT group than that in the CT group (5.7% vs. 22.8% and 36.23°C vs. 35.89°C, respectively). The intraoperative body temperature decreased less (0.32°C vs. 0.69°C), the recovery time from anesthesia was faster (12.8 minutes vs. 17.1 minutes), and the incidence of postoperative shivering was less (2.8% vs. 28.6%) in the FT group than the CT group. In elderly patients undergoing laparoscopic radical resection of colorectal cancer, use of forced-air warming blankets combined with conventional warming measures is more effective to maintain normal body temperature during the perioperative period and reduce the incidence of IPH.

Characterization of Buriti (Mauritia flexuosa) Foam for Thermal Insulation and Sound Absorption Applications in Buildings

Exploring new construction materials with low environmental impact leads to innovation in buildings and also to the expansion of environmental sustainability in the construction industry. In this perspective, the thermal insulation and the sound absorption performances of Buriti (Mauritia flexuosa) foam were analyzed for potential application in buildings. This material is of plant origin, it is natural, renewable, abundant, and has a low environmental impact. In this research, characterizations were made by scanning electron microscopy (SEM), apparent density, thermogravimetry (TGA and DTG), thermal conductivity, and sound absorption. The SEM analysis revealed a predominantly porous, small, and closed-cell morphology in the vegetable foam. Due to its porosity and lightness, the material has an apparent density similar to other thermal insulating and sound-absorbing materials used commercially. The evaluation of thermogravimetric (TGA/DTG) results demonstrated thermal stability at temperatures that attest to the use of Buriti foam as a building material. Based on the thermal conductivity test, the Buriti foam was characterized as an insulating material comparable to conventional thermal insulation materials and in the same range as other existing thermal insulators of plant origin. Concerning sound absorption, the Buriti foam presented a low performance in the analyzed frequency range, mainly attributed to the absence of open porosity in the material. Therefore, understanding the sound absorption mechanisms of Buriti foam requires further studies exploring additional ways of processing the material.

Geopolymer Foams-Will They Ever Become a Viable Alternative to Popular Insulation Materials?-A Critical Opinion.

Over the last several years, there has been a large increase in interest in geopolymer materials, which are usually produced from waste materials, and their applications. The possibilities of application of geopolymers seem to be unlimited, and they are used in almost all fields of technology. Their use as insulation materials appears promising due to their complete nonflammability and excellent strength. However, one limitation is their complex manufacturing process and lack of stability of the obtained geopolymer foams as well as difficulties in achieving such good insulation properties possessed by polyurethane foams, polystyrene, and wool. Hundreds of studies have already been performed on insulating geopolymer foams and various types of foaming agents, and their authors reported that foamed insulating geopolymers had a density starting from 200 kg/m3 and thermal conductivity from 0.04 W/mK. However, the repeatability of the obtained results on an industrial scale is questionable. It is still a challenge to obtain a geopolymer material with comparable properties as conventional insulation materials and to overcome the barriers associated with the successful implementation of geopolymer material as insulation in buildings and other applications on a mass scale. This paper provides a comprehensive review of the methods used for the production of foamed geopolymers and the best parameters obtained, as well as a summary of the most important information reported in the scientific literature. It also presents the results of a critical analysis of the feasibility of implementing this technology for mass deployment. In addition, the problems and limitations that are most often encountered with the implementation of geopolymer technology are discussed.

Paludiculture as paludifuture on Dutch peatlands: An environmental and economic analysis of Typha cultivation and insulation production

Paludiculture, the cultivation of crops on rewetted peatlands, is often proposed as a viable climate change mitigation option that reduces greenhouse gas emissions (GHGe), while simultaneously providing novel agricultural business options. In West Europe, experiments are ongoing in using the paludicrop cattail (Typha spp.) as feedstock for insulation panel material. Here, we use a Dutch case study to investigate the environmental potential and economic viability of shifting the use of peat soils from grassland (for dairy production) to Typha paludiculture (for cultivation and insulation panel production). Using a life cycle assessment and cost-benefit analysis, we compared the global warming potential (GWP), yearly revenues and calculated Net Present Value (NPV) of 1 ha Dutch peat soil used either for dairy production or for Typha paludiculture. We estimated that changing to Typha paludiculture leads to a GWP reduction of ~32% (16.4 t CO2-eq ha−1), mainly because of lower emissions from peat decomposition as a result of land-use management (−21.6 t CO2-eq ha−1). If biogenic carbon storage is excluded, the avoided impact of conventional insulation material is insufficient to compensate the impact of cultivating and processing Typha (9.7 t CO2-eq ha−1); however, this changes if biogenic carbon storage is included (following PAS2050 guidelines). Typha paludiculture is currently not competitive with dairy production, mainly due to high cultivation costs and low revenues, which are both uncertain, and will likely improve as the system develops. Its NPV is negative, mainly due to high investment costs. This can be improved by introducing carbon credits, with carbon prices for Typha paludiculture (30 years) comparable to EU-ETS prices.In conclusion, Dutch Typha paludiculture has a significant climate change mitigation potential by reducing emissions from deep drained peatlands. Nevertheless, attention is needed to increase its economic viability as this is a key aspect of the system change.

Superinsulation Materials for Energy-Efficient Train Envelopes

While traction energy is the main energy used in passenger trains, the energy required to condition the passenger area is significant and can account for up 40% of the total energy use. Due to space constraints, passenger train envelopes are usually only insulated with a few centimetres of conventional insulation materials, leading to relatively high U-values and high energy transmissions in climates where heating or cooling is necessary. Here, the use of superinsulation materials in trains for heating/cooling demand reduction was evaluated. Selected commercially available superinsulation materials were screened and benchmarked in terms of thermal conductivity, fire safety, behaviour under vibration and preferred use position within the train envelope. Both the specific vacuum insulation panels and silica aerogel boards that were tested were found suitable for the application in train envelopes in terms of their thermal, fire and mechanical properties. While vacuum panels have the best insulation performance, aerogel boards offer higher flexibility during installation and reduced risk of damage-related performance loss. Both materials can greatly enhance the energy efficiency and thermal comfort of trains and can be implemented cost-neutrally. However, new policy frameworks are likely to be necessary to promote energy efficiency and the broad implementation of thermal superinsulation in trains.

On the Retrofit of Existing Buildings with Aerogel Panels: Energy, Environmental and Economic Issues

Among the super insulating materials, aerogel has interesting properties: very low thermal conductivity and density, resistance to high temperatures and transparency. It is a rather expensive material, but incentives in the field can improve its economic attractiveness. Starting from this, the thermal behavior of a test building entirely insulated with aerogel panels was investigated through an extended experimental campaign. A dynamic simulation model of a case study building was generated to better comprehend the energy savings obtained through aerogel in terms of energy demand over a whole year. The investigation was completed by computing the carbon and energy payback times of various retrofit strategies through a life cycle assessment approach, as well as by a cost-benefit analysis through a probabilistic financial framework. Compared to conventional insulation materials, aerogel is characterized by a higher energy and carbon payback time, but it guarantees better environmental performance in the whole life cycle. From an economic-financial perspective, the aerogel retrofit is the best in the current tax incentive scenario. However, due to its higher lump-sum investment, aerogel’s net present value is very sensitive to tax deductions, and it is riskier than the best comparable materials in less favorable tax scenarios.

Dielectric Characteristics of Liquid Nitrogen/Synthetic Paper Composite Insulation System for Extra High Voltage HTS Cable

For extra-high-voltage high-temperature superconducting (HTS) cables, not only high electrical insulation performance but also low dielectric loss is required. Therefore, we focus on a porous synthetic paper with lower dielectric loss, e.g., Tyvek polyethylene nonwoven fabric, than that of polypropylene laminated paper (PPLP), which has been used for a conventional HTS cable insulation system. In this paper, we compare partial discharge inception characteristics for different liquid nitrogen/synthetic paper composite insulation systems. The partial discharge inception electric field strength in the composite insulation system depends on the electric field strength in the porous area of synthetic paper.

Can vacuum insulation panels be cost-effective when applied in building façades?

A key factor for achieving nearly-zero energy buildings is to reduce their energy demand using highly efficient thermal insulation materials, such as vacuum insulation panels (VIPs). Currently, the high investment cost of VIPs is hindering the technology penetrating the building market. However, their high thermal performance coupled with reduced thicknesses can lead to economic benefits associated with space savings, significantly changing the economic standing of VIPs. This study presents a comprehensive life cycle cost (LCC) analysis of the application of VIPs in external thermal insulation composite systems (ETICS) in office building façades performed from the landlord perspective. The proposed LCC methodology, based on the EU cost-optimal regulation, allows for comparing the cost-effectiveness of VIPs with conventional insulation materials, taking full account of the additional rental income due to space savings. Energy calculations are performed based on transient heat transfer. The study takes into account varying parameters, such as location, cost of materials, insulation thickness, and rental prices, among others. The results demonstrate that VIPs can be economically viable, in particular in cities where office full-leasing rental prices are high. The range of VIP and rental prices that make their use in buildings cost-effective are identified. For example, it is shown that for rental costs higher than 350 €/(m2.y) VIP can be cost-effective for a current market price of 3000 €/m3, when local climate demands for thermal transmittance bellow 0.19 W/(m2.K). This analysis is useful for VIP manufacturers, project owners and landlords that may be looking for competitive insulation products.

Effect of cellulose fibre based insulation on thermal performance of buildings

Cellulose fibre based insulation can be employed to maintain comfortable indoor conditions inside buildings and to improve energy efficiency. The huge energy consumption for space cooling can be decreased by applying cellulose fibre as thermal insulation in the buildings because of its low thermal conductivity. Cellulose fibre insulation is made from recycled paper fibres and inorganic additives are used to prevent mould growth and increase fire resistance. Here an effort has been made to examine the suitability of cellulose fibre as an insulation for buildings under static, dynamic heat transfer conditions, embodied energy and environmental pollution aspects are also examined. Cellulose fibre insulation has lower value of embodied energy and environmental impact as compared to other insulation materials. Cellulose fibre has lower embodied energy than the conventional and unconventional insulation materials. Cellulose fibre can be utilized in the buildings for maintaining a steady humidity value in the indoor air. Cellulose fibre board has the mean thermal conductivity equivalent to materials like cork, polyurethane, recycled glass, recycled cotton and glass wool. The cellulose fibre board has incredibly low mean thermal diffusivity than other materials like cork, polyurethane, recycled glass, recycled cotton and glass wool. Consequently cellulose fibre has similar thermal performance under static heat transfer conditions to the best insulation materials and the thermal performance of cellulose fibre for insulating buildings under dynamic heat transfer conditions will be much better than other insulation materials. Cellulose fibre is also environment friendly, renewable, recyclable and has lower embodied energy.

Investigation of 2D Nano-Structured Winding Insulation for High Torque Density Medium-Voltage Motor

Since the introduction of mica paper and synthetic resin-based taping insulation for rotating-machines in 1950s, only evolutional improvements in their properties and processing have been made. Due to its challenging nature, much of recent insulation research has been focused on the aspect of reliability rather than performance enhancement. This paper presents the development and performance evaluation of a revolutionary nanostructured insulation in the manufacturing of large propulsion motors with game-changing torque density and payload efficiency for marine Next Generation Integrated Power System. It is demonstrated that nanostructured insulation based on 2D-platelet fillers could offer significant improvement over conventional insulation system in electrical, dielectric, thermal and mechanical properties. Optimal nanostructured insulation formation identified through a Design of Experiment study exhibits high thermal conductivity of >0.8 W/(m·K), high breakdown strength of >40 kV/mm, low dielectric constant of less than 5.5 and low dielectric loss factor of less than 2.5% at 155°C. Voltage endurance tests on coupons with optimal formulation, in accordance with IEC 60343 standard, demonstrate satisfactory endurance life. Furthermore, a multi-physics finite-element-analysis model of the winding in a medium-voltage electric motor is established to perform electromagnetic and thermal analyses in ANSYS under various temperature boundary conditions. The study indicates a remarkable increase of 14% in torque handling capacity of a motor wound with proposed nanostructured insulation material when compared to an identical motor wound with conventional micaceous insulation.

Comparative life cycle assessment of different vacuum insulation panel core materials using a cradle to gate approach

The global market trend for Vacuum Insulation Panels (VIPs) is projecting a significant increase in their uptake in the construction sector. This is mainly due to the uniquely high-performance properties of the ultra-thin insulation materials. This uptake, however, can potentially be hindered by the VIPs’ higher cost and environmental impacts when compared with conventional insulation materials. This paper, for the first time, presents a detailed evaluation of the environmental impact of the most common type of VIPs currently used in different applications with a focus on alternating the core material as the main contributing component to their footprint. Pyrogenic silica, glass fibre, expanded polystyrene, aerogel and a silica/sawdust hybrid core were analysed from cradle to gate. The study, on a comparative basis, demonstrates the sensitivity of the various environmental impact categories to the internal vacuum pressure and the subsequent thermal conductivity values. The results show a lower environmental impact for glass fibre and low density expanded polystyrene compared to the other alternatives. Pyrogenic silica, the most common core material, had the highest environmental impact out of the core materials considered. The higher environmental impacts of pyrogenic silica suggest that measures such as the recycling of the core material alongside the deployment of eco-friendlier manufacturing techniques should be considered if the material is to compete environmentally with the other alternative materials.

Solid Media Thermal Energy Storage System for Heating Electric Vehicles: Advanced Concept for Highest Thermal Storage Densities

The integration of thermal energy storage systems enables improvements in efficiency and flexibility for numerous applications in power plants and industrial processes. By transferring such technologies to the transport sector, existing potentials can be used for thermal management concepts and new ways of providing heat can be developed. For this purpose, technology developments for solid media high-temperature thermal energy storage systems are taking place for battery-electric vehicles as part of the DLR Next Generation Car (NGC) project. The idea of such concepts is to generate heat electrically, to store it efficiently and to discharge it through a bypass concept at a defined temperature level. The decisive criterion when using such solutions are high systemic storage densities which can be achieved by storing heat at a high temperature level. However, when storing high temperature heat increasing dimensions for thermal insulation are required, leading to limitations in the achievable systemic storage density. To overcome such limitations, an alternative thermal insulation concept is presented. Up to now, conventional thermal insulations are based on sheathing the storage containment with efficient thermal insulation materials, whereby the thickness results from safety restrictions with regard to the permitted maximum surface temperature. In contrast, the alternative concept enables through the integration of the external bypass into the thermal insulation systemic advantages during the charging and discharging period. During discharging, previously unused amounts of heat or heat losses within the thermal insulation can be integrated into the bypass path and the insulation thickness can be reduced during loading through active cooling. Using detailed models for both the reference and the alternative thermal insulation concept, systematic simulation studies were conducted on the relevant influencing variables and on the basis of defined specifications. The results confirm that the alternative thermal insulation concept achieves significant improvements in systemic storage densities compared to previous solutions and high potentials to overcome existing limitations.

Titania‐based transformer nanofluid: a study on the synthesis for enhanced breakdown strength and its humidity ageing

Researches on the transformer oil-based nanofluids to determine its suitability for replacing the conventional liquid insulation has been consistently happening for more than a decade. Yet, to prepare an optimum blend of transformer oil-based nanofluid with the stability compliance and superior breakdown (BD) characteristics is still a key issue to be addressed. So to achieve the higher BD voltages (BDVs) with good stability, the nanoparticle and surfactant weights dispersed in the oil should be optimised to at least possible critical levels. In this work, dielectric BD characteristic of mineral oil dispersed with TiO2 nanoparticle and surfactant cetyl trimethyl ammonium bromide (CTAB) is been studied with the applied AC and DC high voltages, which is termed as titania-based transformer nanofluid (TTNF) for this study. Series of TTNF samples were synthesised with different weights of TiO2 nanoparticle and CTAB, and the partial discharge inception voltage, AC and DC BDV were experimented to ascertain the optimum concentration level. Results show that the AC and DC BDV enhanced up to 36.23 and 43.07%, respectively, for the TTNF prepared with 0.00562 wt% of TiO2 and its 1% weight of CTAB, which was stable for around eight weeks.

Numerical Studies of the Electric Field of a Power Cable with Sector Strands and Impregnated Paper–Plastic Insulation for a Voltage of 20 kV

In power cables with sector current-carrying strands (SCSs), impregnated with paper insulation, there is a tangential electric field component along the layers. The permissible electric strength along the paper tapes is about ten times less than in the normal direction, which is taken into account when developing three-wire power cables impregnated with paper insulation for voltages of 20 and 35 kV. The use of modern paper—plastic-impregnated insulation having higher performance characteristics than conventional impregnated paper insulation, can promote the creation of more efficient cable designs with individually shielded sector-shape conductors in a common lead sheath for a voltage of 20 kV. Each insulated strand of such cables has a copper shield, and so it is enough to consider the electric field in the cross section of the insulation of one SCS. The electric potential distribution is described by the Laplace differential equation, the solution of which is implemented by the finite element method using the Ansys Maxwell software package. A numerical study of the electric fields has been carried out for power cables with SCSs that have a cross section of 400 mm2 for a voltage of 20 kV. The curvature radius of the cable sectors varied from 5 to 7 mm with an insulation thickness of 7 to 9 mm. Based on the research results, the maximum values of the normal and tangential electric field components depending on the curvature radius of the sector strand and insulation thickness have been obtained. Insulation areas have been allocated in which the maximum absolute values of the tangential electric field strength components have been observed. The allowable values of the sector curvature radius and the thickness of insulation for power cables with paper-impregnated insulation for 20 kV have been determined.