Electrical Cable Insulation Research Articles

Poly(vinyl chloride) Dechlorination Catalyzed by Zirconium.

Poly(vinyl chloride) undergoes dechlorination in the presence of triethylsilane (Et3SiH) and a catalytic amount of [Cp2Zr(NPh2)][CH3B(C6F5)3] (1 b) at 40-80 °C, with up to 91 % efficiency. Stoichiometric reactivity studies conducted on cyclohexyl chloride as a model suggest that 1 b dechlorinates PVC by initial chloride abstraction, followed by hydride transfer to the cationic PVC chain from Et3SiH. Consumer items such as pipe fitting, vinyl disc or electric cable insulation undergo either dechlorination or hydrosilylation of the carbonyl-containing copolymer (polyvinyl acetate) or plasticizer (phthalate).

Parameters that influence the partial discharges occurrence in cavity defect within electrical cable insulation

Parameters that influence the partial discharges occurrence in cavity defect within electrical cable insulation

Properties and Uses of Biochars Incorporated into Mortars

The construction industry is responsible for a large amount of CO2 emissions and an intensive energy consumption. Cement production is the third largest source of anthropogenic CO2 emissions and is responsible for about 1.8 Gt of CO2 emissions into the atmosphere. The use of waste materials to replace a fraction of cement in the mortar makes it more economically and ecologically friendly. In this work, the main objective was to test incorporations of biochar produced at temperatures of 300, 350, and 400 °C, as a partial replacement for cement in the production of mortar. The materials used for the tests were residual lignocellulosic biomass (WBL) and electrical cable insulation waste (WIEC) mixed in a ratio of 1:1. The biochars produced were crushed and sieved after production to reduce the particles. A sample of biochar was used and tested under these conditions and another sample was washed in water and dried before being incorporated; all tests were carried out with a 5% replacement. Waste recovery tests were also carried out without thermochemical treatment. The specimens were studied for compressive strength and water absorption by immersion. All tests were replicated and were analyzed and compared with a control mixture with no incorporation of biochar in the mixture. It was possible to observe that the tests with the incorporation of biochars at 400 °C showed better results, with only a 24% reduction in resistance to compression.

Characterization and Identification of Electrical Tree Growth Stages Inside High-Voltage Cable Insulation

Characterization and Identification of Electrical Tree Growth Stages Inside High-Voltage Cable Insulation

Canopy bridges: preventing and mitigating anthropogenic impacts on mantled howler monkeys (Alouatta palliata palliata) in Costa Rica

Abstract Increasing levels of anthropogenic modification, degradation, and fragmentation of arboreal mammal habitats substantially influence wildlife movement and behavior. In Costa Rica, there has been a surge in infrastructure development in the past decade. This infrastructure puts wildlife at high risk of mortality from electrocution, vehicle collisions, falls, and attacks by domestic animals. To prevent and mitigate the mortality of arboreal animals, canopy bridges have been implemented in several parts of the country. In Playa Hermosa, Guanacaste, a coastal community, we implemented a canopy bridge project for mantled howler monkeys (Alouatta palliata palliata). For the first year of our study (2015-2016), we performed monthly three-day censuses and follows of all howler monkey groups. After the first five months of data collection, we identified 20 high-use arboreal pathways that would benefit from reinforcement with canopy bridges and installed camera traps in the pathways to verify their use outside of sampling periods. After use was verified, we installed canopy bridges at those 20 sites. We continued to identify high-use paths via group follows, ad libitum sightings from community members, and annual group censuses between 2018 and 2021 and installed an additional 91 bridges (N = 111 total). We also developed a system for community reporting of howler monkey injuries and fatalities and advocated for better insulation of electric cables, with 8341 m insulated between 2015 and 2021. Between 2015 and 2021, we saw the number of monkey groups grow from five to seven, group home ranges grow, the population grow from 59 to 99, and fatalities decrease from five to one annually. We conclude that the bridges likely contribute to howler monkey population growth via decreased fatalities and safer access to feeding resources and mates. Costa Rica is currently adopting legislation to make connectivity mitigation measures for wildlife mandatory in infrastructure development, making it a global leader.

Polyethylene crosslinking using the epoxy‐anhydride reaction I: A strategy for a curing process with high thermal sensitivity

AbstractThe initiated epoxy‐anhydride reaction was examined as a crosslink motif for effecting cure in functionalized polyethylene for electrical cable insulation applications. A specific challenge for this application is that little to no crosslinking can occur during the processing steps (~140°C), but crosslinking must be rapid and complete within a few minutes during the curing process (~200°C). To achieve this, we coupled the kinetics of the formation of an initiator for the epoxy‐anhydride reaction to the crosslinking step to achieve a phenomenological temperature sensitivity or “latency” that would be difficult to access via a single simple reaction. Evaluations of different imidazolium and phosphonium salts as initiator precursors were conducted with model compounds in solution, and specific salts were chosen for polymer studies based on the ratio of the phenomenological rates measured for the model reaction at ~140°C and ~200°C. In polymer studies using epoxide‐functional poly(ethylene), high crosslinking rates were observed at ~200°C while crosslinking was minimal at ~140°C. However, inclusion of the anhydride‐functional polyethylene in the formulation led to loss of initiator latency, and significant crosslinking was observed at ~140°C. A reaction between the anhydride or an impurity and initiator precursor is postulated to produce a kinetically‐competent initiator at lower temperatures that destroys latency.

Use Of Micro-Void Content Growth Rates To Validate And Add Value To Electrical Insulation Tan-Delta Aging Testing

Our research as well as others has shown that micro-void content in electric insulation polymers grows in a way that can be correlated to the degree of aging. Specific results of our experiments combined with research by others have led us to conclude that a promising technique for predicting remaining life in electric cable insulation, based on micro-void content and proximity to void limiting parameters, can be developed. This approach involves use of acoustic or optical microscopy to establish an estimate of void content in polymers by determining micro-void sizes and density. Separate research is used to establish limiting values for percent void content correlating to material failure. The mode of failure varies depending on the applied voltage regime. For example, at medium and high voltage levels, partial discharge detection can be considered indicative of pending end of life. Whereas for low voltage regimes, brittleness to the point of cracking susceptibility would allow the potential for moisture ingress and shorting and can be considered end of life. It has been separately shown that void growth rate is a function of temperature and radiation dose rate both during normal and nuclear accident conditions and is predictable based on the known polymer chemical degradation equations, which produce gaseous products in the form of oxygen, water vapor, carbon dioxide, and carbon monoxide. Thus if end of life void content is known, the degree of void content growth occurring during a design basis accident is properly accounted for, and void content growth rates during normal temperature and radiation conditions are considered, then remaining life in electrical insulation can be accurately predicted. In recent years, several techniques have been proposed to assess electrical insulation aging. One of the more promising approaches for use with medium voltage cable is the tan-delta technique. This paper will demonstrate how the mirco-void content approach can be used to validate other techniques such as tan-delta and add additional meaning and value not otherwise available from tan-delta alone.

Thermal aging of electrical cable insulation made of cross‐linked low density polyethylene for under‐hood application in automotive industry

AbstractThe thermal aging of two electrical cable insulations made of cross‐linked low density polyethylene (XLPE) only differing by their stabilization system was studied in air between 125 and 200°C. The chemical consumption of the two types of antioxidants (phenol and sulfide), the build‐up of oxidation products and the consequences of thermal oxidation on the mechanical properties were respectively determined by measurement of the oxidation induction time (OIT), Fourier transform infrared spectroscopy (FTIR) and uniaxial tensile testing. It was found that the chemical consumption of each antioxidant occurs in turn almost independently, starting with the sulfide antioxidant and involving small but well detectable antagonistic effects. As soon as the antioxidant concentration becomes very low, that is, practically undetectable by OIT measurements, the thermal oxidation of XLPE is detected by FTIR spectroscopy causing a catastrophic decrease in the fracture properties. It was shown that the complete consumption of antioxidants coincides with the end of the oxidation induction period and the onset of the sudden decrease in the elongation at break. Based on all these experimental results, a simplified kinetic model was developed to account as faithfully as possible for the consumption kinetics of antioxidants, evaluate their antagonistic effects and, using a relevant end‐of‐life criterion, predict the lifetime of the two XLPE insulations. It was found a satisfying agreement between theory and experiment.

Evaluation of Copper Catalytic Effects in Cable Insulation Polymers

This article summarizes work performed to evaluate a phenomenon that occurs in electrical cable insulation polymers subjected to accelerated aging while in contact with copper metal. This effect, commonly known as the copper catalytic effect, is a result of chemical reactions that occur when copper ions diffuse into insulation polymers. This diffusion process is observed in various types of polymeric materials exposed to elevated temperatures and happens at the interface between the insulation and metallic components (e.g., conductor and shielding) in a cable. This polymer–metal interaction has only been observed in cables constructed with copper components (i.e., no interactions observed in cables with aluminum or other metal conductor/shielding) and results in a significant catalytic effect that increases the oxidation rate (e.g., aging) of the material. Under this research, the copper catalytic effects observed in cross-linked polyethylene, cross-linked polyolefin, and ethylene-propylene rubber insulated cables subjected to thermal accelerated aging were evaluated. These evaluations involved applying infrared spectroscopy, microscopy, and energy-dispersive X-ray spectroscopy cross-sectional depth profiling to obtain an in-depth understanding of the aging characteristics of the materials under accelerated conditions. Based on the results of these assessments, the copper catalytic effect can have a significant impact on the mechanical, thermal, chemical, and electrical properties of cable insulation polymers. The results acquired from this research provided the information needed to characterize the copper catalytic effects observed in these polymers, analyze how this phenomenon affected the polymer degradation process, and compare and understand the differences in the properties of the materials.

ТЕРМОФЛУКТУАЦИОННАЯ ТЕОРИЯ РАЗРУШЕНИЯ И ОЦЕНКА ДОЛГОВЕЧНОСТИ ЭЛЕКТРИЧЕСКОЙ ИЗОЛЯЦИИ СПЭ КАБЕЛЕЙ

The article is devoted to research on the creation of a method for assessing the durability ofthe main insulation of power cable lines based on the thermofluctuation theory of destruction of solids.The features of breakdown development in homogeneous and inhomogeneous dielectrics areconsidered. The problematic issues of insulating materials of power cable systems (PCS) are consideredon the basis of the development and development of non-destructive testing methods. The maincomponents that destroy the insulation of the PCS are installed. The thermofluctuation theory ofdestruction and the evaluation of the durability of electrical insulation of power cables are described.An analytical method is proposed for evaluating the processes of cellulose oxidation with the determinationof the most probable. The proposed approach to identifying the main processes of insulationdestruction allows us to present in more detail the prerequisites for the development of partial discharges(PD) in isolation and to determine measures to minimize the processes leading to the destructionof PCS insulation. The results of experiments on the study of the service life of the insulatingmaterial of aged ends of a power cable in a thermal cabinet, to determine the aging criteria, arepresented. The experimental data are interpreted from the standpoint of the thermofluctuation theory.The dependence of the increase in the temperature difference ΔT on the degree of wear of the electricalinsulating properties of the material is revealed and investigated, which makes it possible to predictits resource. The thermofluctuation theory of the destruction of insulating materials caused bythe thermofluctuation rupture of chemical bonds and the evaluation of the durability of electricalinsulation of cables made of cross-linked polyethylene are considered. It is shown that, in order tocalculate the average energy of the monomeric link of various polymer materials, it is necessary toknow: the chemical formula of the monomeric link and the values of the binding energies. In thework, the time before the breakdown of the main insulation of the PCS was determined under theaction of temperature. The model can be used in devices and systems for continuous diagnosis ofpower cables according to temperature conditions.

Method for assessing the state and residual life of the insulation based on analysis of the time of discharge of the capacity of electric cables

As of today, the problem of the lack of non-destructive methods for assessing the state and determining the residual life of the insulation of electrical cables is relevant for cable lines in operation, and especially for lines that have exhausted their service life. The research presented in the framework of this article is aimed at creating a non-destructive technique for assessing the state and residual life of electrical cables insulation. The study was carried out using computer simulation methods and using the basic theoretical laws of physics and electrical engineering. A method for assessing the condition and residual life of electrical cable insulation has been developed, which is based on the analysis of the discharge time of the cable capacity. The applicability of the method is determined, instructions are given on its applicability and the analysis of the output data. The obtained results can be used by power grid companies and industrial enterprises to analyze the state of the insulation of electrical cables.

A new analytical model for predicting the radio-thermal oxidation kinetics and the lifetime of electric cable insulation in nuclear power plants. application to silane cross-linked polyethylene

The radio-thermal oxidation of silane cross-linked polyethylene (Si-XLPE) was studied in air under different γ dose rates (6.0, 8.5, 77.8, and 400 Gy.h−1) at different temperatures (21, 47, and 86°C). The changes in the physico-chemical and mechanical properties of Si-XLPE throughout its exposure were determined by FTIR spectroscopy, differential scanning calorimetry (DSC), swelling measurements, rheometry in rubbery (DMTA) and in molten states, and uniaxial tensile testing. It was found that oxidation leads to the build-up of a wide variety of carbonyl and hydroxyl products (mostly carboxylic acids and hydroperoxides) and an efficient chain scission process that catastrophically reduces the concentration in elastically active chains and the elongation at break from the early periods of exposure. A new analytical model was derived from the current radio-thermal mechanistic scheme without making the usual assumption of thermal stability of hydroperoxides. After an initial period where the oxidation kinetics occurs with a constant rate, this model allows also predicting the auto-acceleration of the oxidation kinetics when the hydroperoxide concentration reaches a critical value of about 1.6 × 10−1 mol.L−1. Choosing this critical value as a structural end-of-life criterion allows a more direct assessment of the lifetime of Si-XLPE in the various radio-thermal environments under study, except at the highest temperature (i.e. 86°C) where the kinetic model can still be noticeably improved.

Recycling of waste poly(vinyl chloride) fill materials to produce new polymer composites with propylene glycol plasticizer and waste sawdust of Albizia lebbeck wood

Plastic waste management is a burning issue nowadays. In this study, new wood-plastic composites were made using waste poly(vinyl chloride), plasticizer and waste sawdust of Albizia lebbeck wood at different weight percentages (0%, 1%, 2%, 5%, 10%, and 15%) by mechanical recycling process. At first, waste rigid poly(vinyl chloride) fill materials of cooling tower were cleaned, grinded into recyclates and characterized by physical, mechanical, morphological and attenuated total reflection Fourier transform infrared analyses. Nontoxic plasticizer propylene glycol was added into the waste rigid poly(vinyl chloride) recyclates to make it flexible and investigated its addition effect on the tensile, thermal and morphological properties of rigid poly(vinyl chloride). Results indicated that, the addition of plasticizer reduced the tensile strength and thermal stability of the waste poly(vinyl chloride). Lebbeck wood sawdust reinforced propylene glycol plasticized waste poly(vinyl chloride) composites were prepared via solution casting method and their mechanical, thermal and morphological characteristics were investigated. Tensile strength of the composites was found to be increased significantly for 1 ​wt% sawdust reinforced plasticized waste poly(vinyl chloride) composites. Thermogravimetric analyses showed increased thermal stability for 1 ​wt% sawdust reinforced plasticized waste poly(vinyl chloride) composite than the plasticized neat poly(vinyl chloride). Morphological analyses of the composites also revealed the better result for 1 ​wt% sawdust reinforced plasticized waste poly(vinyl chloride) composites. The produced recycled plasticized poly(vinyl chloride) composites can be used in electrical cable insulation, packaging and automotive applications with cost and environmental benefits.

3D Model of partial discharge in defects with different sizes and positions in power cable for distribution and transmission networks

The knowledge of partial discharge (PD) phenomena inside electrical insulation of power cables is an important issue for assessing the insulation condition and its degradation state, obtaining information about the likelihood of failure. PDs cause signals to propagate along the cable, as noise phenomena, and contribute to the insulation degradation, culminating in a disruptive fault with the interruption of power supply. Therefore, PDs are considered the best ‘early warning’ indicators of insulation degradation and their modelling, with the development of on-line PDs location methods, are important topics to increase the networks’ electricity security. In this study, a three-dimensional (3D) model of PD events using the CST STUDIO® Dassault software is proposed. PDs inside air inclusions in epoxy-resin are analysed with different shapes, positions and sizes of the defect. The electric-field distribution is evaluated with the conduction current inside the void and the apparent charges induced on the electrode. The effectiveness of the model is validated by comparing the simulation results with other published experimental results. Finally, a description of a 3D–1D hybrid model useful to describe the propagation of PD signals in power networks is given.

Improving Mechanical Properties and Reaction to Fire of EVA/LLDPE Blends for Cable Applications with Melamine Triazine and Bentonite Clay.

The high flame-retardant loading required for ethylene-vinyl acetate copolymer blends with polyethylene (EVA-PE) employed for insulation and sheathing of electric cables represents a significant limitation in processability and final mechanical properties. In this work, melamine triazine (TRZ) and modified bentonite clay have been investigated in combination with aluminum trihydroxide (ATH) for the production of EVA-PE composites with excellent fire safety and improved mechanical properties. Optimized formulations with only 120 parts per hundred resin (phr) of ATH can achieve self-extinguishing behavior according to the UL94 classification (V0 rating), as well as reduced combustion kinetics and smoke production. Mechanical property evaluation shows reduced stiffness and improved elongation at break with respect to commonly employed EVA-PE/ATH composites. The reduction in filler content also provides improved processability and cost reductions. The results presented here allow for a viable and halogen-free strategy for the preparation of high performing EVA-PE composites.

Desarrollo de compuestos XLPE con retardantes de llama de baja toxicidad para aislamiento de cables

Se desarrollaron nueve formulaciones de un masterbatch retardante a la llama de bajo impacto medioambiental y se evaluó la influencia de su incorporación en un polietileno lineal de baja densidad, injertado con un agente de entrecruzamiento viniltrimetoxisilano, para su posterior reticulación con el fin de obtener un polietileno entrecruzado con retardancia a la llama. Los masterbatch retardantes a la llama se prepararon a partir del uso de N, N-etilen bis(tetrabromoftalamida), mezclado con: trióxido de antimonio, borato de zinc, polietileno lineal de baja densidad, agente de dispersión y cera polietilenica, variando el N,N-etilen bis(tetrabromoftalamida) (36, 42 y 45 %) y el agente de dispersión (0.50, 1.25 y 2.00 %), mientras se mantuvo constante el resto de componentes. Posteriormente, los nueve masterbatch desarrollados se mezclaron con el polietileno lineal de baja densidad injertado para la producción de nueve compuestos de polietileno entrecruzado retardante de lama que luego se conformaron en forma de placas y aislamiento de cable 14 AWG para su caracterización fisicoquímica. Se encontró que el nivel empleado tanto en las cargas (N,N-etilen bis-tetrabromoftalamida, trióxido de antimonio y borato de zinc) como en el agente de dispersión condicionaron el nivel de entrecruzamiento estimado a partir del contenido de gel, las características de flujo y el comportamiento frente a la llama del material; siendo favorecidas las primeras dos propiedades con el incremento del agente de dispersión, en tanto que la última se vio mejorada con el aumento en la proporción de las cargas usadas. De igual manera, la evaluación de un compuesto de polietileno entrecruzado retardante a la llama fabricado con un masterbatch retardante a la llama comercial, tomado como referencia, evidenció que algunas de las formulaciones trabajadas en esta investigación son susceptibles de ser empleadas para el aislamiento de cables eléctricos.

Temperature State of a Hollow Cylinder Made of a Polymer Dielectric with Temperature-Dependent Characteristics

A mathematical model is constructed to describe a steady one-dimensional temperature distribution in a hollow circular cylinder made of a polymer dielectric with a constant difference in the electric field potentials on the cylinder surfaces. Based on systematized data on the dependence of the thermal conductivity and electrical conductivity of polymer materials used as dielectrics in engineering on temperature, a qualitative analysis of the model is performed for a prescribed density of the heat flux supplied to the inner surface of the cylinder and intensity of convective heat transfer on the outer surface The results obtained in the study allow one to determine the area of applicability of polymer dielectrics used in various electrical engineering applications, including electrical insulation of DC high-voltage cables, and to formulate the conditions for the thermal breakdown of the cylindrical layer of the dielectric.

New mathematical models for predicting the lifetime of EPDM insulators: Effect of elongation at break on the kinetic degradation of EPDM insulators subjected to thermo-oxidation

Ethylene propylene diene monomer (EPDM) is an important polymer extensively exploited in plasturgy. However, relatively few studies have been carried out to predict the lifetime of EPDM in different climatic conditions particularly, thermo-oxidation. Based on this realization, the aim of the present work was to develop mathematical models for predicting the lifetime of EPDM elastomers, used for insulation of electric cables. The kinetic degradation of EPDM insulators, by monitoring change in a physical property (elongation at break test “ℇr”), was studied by following its thermo-oxidative aging (70, 90, 110 and 130 ° C in air circulating oven). The multiple linear regression analysis (MLRA), solved by the Cholesky method, was the mathematical approach developed in the modeling of the kinetic degradation. In this study, we used two insulators materials when the first insulator contained an amorphous EPDM and the second contained a semi-crystalline EPDM. The results showed that the polynomial models developed to predict elongation at break were reliable for both insulators under thermo-oxidation. The half-life times predicted by the mathematical models was found to be statistically significant (p< 0.05). In conclusion, the mathematical models developed in our study could be used confidently to predict the lifetime of EPDM elastomers.

Critical Heat Flux Determination of Electric Cable Insulation

Abstract Electric cables can contribute to the spread of fire through the insulating layer. This paper focuses on their properties characterizing the initiation of fire. Samples of ethylene-based cable insulation were tested using a cone calorimeter by exposing them to external heat flows of six different values (25 kW m−2 – 50 kW m−2). Time to initiate flame burning was observed. The critical heat flux (depending on the method of calculation was in the range 2.94 kW m−2 – 4.59 kW m−2) and the thermal response parameter (342 kW s−0.5 m−2) was calculated from the time of initiation and external heat flow dependence.

Experimental investigation of using cross-linked polyethylene waste as aggregate in roller compacted concrete pavement

In recent years, cross-linked polyethylene (XLPE) is one such waste material that has been growing rapidly. In fact, XLPE used for the insulation of electric wires and cables is a non-biodegradable component. This study was carried out to investigate the use of XLPE waste as an aggregate in roller compacted concrete pavement (RCCP) mixes. XLPE waste as an aggregate with several volume percentages was utilized to replace the natural coarse aggregate of concrete mix. This replacement was conducted with 5%, 15%, 30% and 50% contents. The unit weight, VeBe time, compressive strength, splitting tensile strength, and flexural strength were measured for all the specimens. The results indicated that the use of XLPE waste changed the properties of fresh and hardened concrete. XLPE waste caused the reduction of unit weight and VeBe time. The results showed that replacing 5% of coarse aggregate with XLPE waste increased the 28-d splitting tensile strength of RCCP by 11%. In addition, the 28-d compressive and flexural strengths of this concrete mix were greater than the minimum compressive and flexural strengths determined by the RCCP guide. According to the test results, the use of XLPE waste for more than 5% of the coarse aggregate of the mix are recommended for low traffic pavements, rural roads and sidewalks. Moreover, the use of XLPE waste increased ductility and resistance against RCCP cracking. Overall, using XLPE waste in RCCP can prevent entering wastes into the environment. And, it reduces landfill cost and saves energy.