Cable Sheath Research Articles

Experimental investigation and numerical modeling of oxidative pyrolysis mechanism of mining PVC cable sheath

Cables modified with flame retardants are widely used in the coal mining process to enhance their fire safety performance. This paper investigates experimentally and numerically the thermo-oxidative degradation process of PVC-based mining cable sheath, which consists of PVC resin and plasticizers (Phthalate esters), fillers (Calcium carbonate), and flame retardant (Antimony trioxide) as additives. Thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) experiments were performed at different heating rates in an air atmosphere. TG results showed that the decomposition processes of mining PVC cable sheath are more complicated than those of pure PVC with additional degradation steps, which was further confirmed by FTIR gas analysis. A deconvolution method was used to distinguish the independent reactions from the overlapped derivative thermogravimetric (DTG) peaks. It was found that the whole degradation process can be divided into seven steps, based on which an oxidative pyrolysis model was developed: pyrolysis of plasticizers (steps 1 and 2), dehydrogenation (step 3), emission and combustion of volatile fraction (step 4), carbon combustion (step 5), oxidative pyrolysis of complicated additives (step 6), and decomposition of residues (step 7). The kinetic triplets (activation energy, pre-exponential factor, and reaction model function) for each reaction were firstly calculated using three commonly used model-free methods and then further optimized using the genetic algorithm (GA). Based on the optimized parameters, the reaction mechanisms and their associated kinetic parameters were determined. The findings of this study are important in understanding the oxidative pyrolysis process of PVC cable sheath, and the obtained kinetic parameters can also be used for its pyrolysis and fire modeling, waste recycling, and risk assessment.

The simulation of electromagnetic interaction of the components of transport electrotexnical complex

Background: The transport electrical complex includes many interconnected infrastructure components that ensure the safety of the operation of the entire system. The issues of protection against electromagnetic influences are becoming more relevant with the growth of traffic intensity.
 Aim: Evaluation of the degree of electromagnetic impact of traction networks on the cable line.
 Materials and Methods: Mathematical modeling is carried out using the finite element method and the COMSOL Multiphysics software package.
 Results: Current distributions in two typical traction power networks are obtained, taking into account the presence of a cable line in the zone of influence. The generated electric and magnetic fields and the parameters of the current induced on the sheath of the cable line are determined.
 Conclusion: The use of mathematical modeling makes it possible to decompose the influences into constituent factors and reveal the internal structure of the mechanism of interaction between the components of the transport electrical complex. The simulation results allow us to confidently fix the induced currents from the force electromagnetic fields on the cable sheath. These studies can be used in the development of modern means of protection.

전선의 허용곡률반경과 턴(TURN)에 따른 발화 가능성 연구

In this paper, two tests were performed using the commonly used HFIX(1.5SQ) cable for the purpose of analyzing the impact of a cable’s Cable Bend Radius and Turn on fire risk. In each test, 14A and 16A stationary electrical currents without a functioning molded case circuit breaker (MCCB) were applied respectively for 180 seconds, and then an infrared camera was used to verify the temperature characteristics and the ignition probability. The results of the tests showed that the Cable Bend Radius, within the scope of not causing physical damage to the copper wire or the cable sheath, did not have meaningful impact upon thermal accumulation. For the Turn however, there was a linear increase in the temperature of the cable even within the range of allowable current of the cable as the number of Turn increased, verifying the risk of fire from the cable sheath. Therefore, to minimize the risk of cable fires, the cable must be correctly used at all times and constant preventive actions through maintenance including regular inspection and repairs are needed.

Radical Composition and Radical Reaction Kinetics in the Probe-Irradiated XLPE Samples as a Potential Source of Information on Their Aging Degree

Polyethylene is a model polyolefin, and a widely used material for the manufacture of many products, including cable sheaths. Understanding degradation mechanisms at the atomic scale leading to oxidation during aging is crucial for many long-term applications. The concentrations of radicals derived from oxidation and chain scission during radio-oxidation, as well as their ratio, are important parameters controlling the predominance of chain scission or crosslinking of the polymer. In this work, we propose a cryogenic EPR technique for measuring oxidation- and fragmentation-derived radicals as a less-destructive method for the evaluation of cable insulation aging and performance capability. We investigate the effect of the low-dose and high-dose radiation aging on the formation of free radicals in the polymer matrix that are both unprotected and protected by antioxidants. The stability of radicals after aging is a determinant of macroscopic processes and structural changes during aging. Under the conditions of the higher dose rate, the peroxy radical buildup is lower per dose. Peroxy radical buildup is followed by decay during aging, in accordance with POOH content. Our results allow the prediction of the capability of the antioxidant to protect the XLPE material in the function of dose and time.

Research on Pyrolysis Characteristics of PE Outer Sheath of High-Voltage Cables Based on the Principle of Oxygen Consumption

Research on Pyrolysis Characteristics of PE Outer Sheath of High-Voltage Cables Based on the Principle of Oxygen Consumption

Oxygen effects on the evolution of hydrogen chloride and chlorine gas during combustion of PVC-CaCO3 based cable

This paper investigates the migration and evolution of chlorinated (Cl-) chemicals during the combustion of polyvinyl chloride-calcium carbonate (PVC-CaCO3) composite cable outer sheath under different oxygen (O2) concentrations. Previous studies have mainly focused on the combustion of cables and subsequent generation of gaseous products under ambient air, and there is limited knowledge on the combustion behavior when the O2 concentration of the combustion air varies, especially at elevated, above ambient level. In this paper, the variations of Cl-contents in the remaining solid residues and Cl-gaseous products were studied under different O2 concentrations and external heat fluxes. The results show that when the O2 concentration increases from 12 to 18 %, the increased surface temperature enhances the pyrolysis rate and the hydrogen chloride (HCl) yield which increases from ∼0.15–0.18 g/g. Over 18–24 % O2 concentration, the HCl yield diminishes sharply and continuously, from ∼0.18–0.13 g/g with increasing O2 concentration. By 30 % O2 concentration, HCl yield has reduced by more than 40 %. Under O2-rich combustion, a large amount of chlorine gas (Cl2) is presence in the combustion products following the reduction in HCl yield, where over 75 % converted HCl was oxidized to form Cl2. HCl competes for O2 which is also required for carbon monoxide (CO) oxidation, and the O2 consumed for HCl oxidation is approximately 3 times that of CO oxidation. Under 12–18 % O2 concentration, the presence of high HCl yield inhibits CO oxidation, resulting in an increase in CO yield with intensified pyrolysis.

Recent Advances in Halogen-Free Flame Retardants for Polyolefin Cable Sheath Materials.

With the continuous advancements of urbanization, the demand for power cables is increasing to replace overhead lines for energy transmission and distribution. Due to undesirable scenarios, e.g., the short circuit or poor contact, the cables can cause fire. The cable sheath has a significant effect on fire expansion. Thus, it is of great significance to carry out research on flame-retardant modification for cable sheath material to prevent fire accidents. With the continuous environmental concern, polyolefin (PO) is expected to gradually replace polyvinyl chloride (PVC) for cable sheath material. Moreover, the halogen-free flame retardants (FRs), which are the focus of this paper, will replace the ones with halogen gradually. The halogen-free FRs used in PO cable sheath material can be divided into inorganic flame retardant, organic flame retardant, and intumescent flame retardant (IFR). However, most FRs will cause severe damage to the mechanical properties of the PO cable sheath material, mainly reflected in the elongation at break and tensile strength. Therefore, the cooperative modification of PO materials for flame retardancy and mechanical properties has become a research hotspot. For this review, about 240 works from the literature related to FRs used in PO materials were investigated. It is shown that the simultaneous improvement for flame retardancy and mechanical properties mainly focuses on surface treatment technology, nanotechnology, and the cooperative effect of multiple FRs. The principle is mainly to improve the compatibility of FRs with PO polymers and/or increase the efficiency of FRs.

Determination Of Flow Velocities Using Fiber-Optic Temperature Measurements

A novel flow measuring technique is introduced to measure under harsh circumstances in environments with dirt, high pressures and elevated temperatures as in boreholes within the earth's crust. A glass fiber embedded in a cable with heating wires measures the temperature within the heated cable with distributed temperature sensing (DTS). Similar to Hot Wire Anemometry, the velocity dependence of convective heat transfer is exploited to measure the velocity of the cable as a cylinder in crossflow. A borehole-mimicking test rig and a realistic prototype of a borehole probe were built and the flow along the borehole axis was investigated. The expected Nusselt Reynolds characteristic of a cylinder in crossflow has been measured which proves the concept of this novel measurement technique. Challenges arise with the insufficient spatial resolution of DTS measurements and in the heat transfer modeling because the temperature profile of the cables cross-section must be taken into account. More detailed investigations and developments are planned to elevate this measurement technique from the current proof-of-concept stage to a reliable flow measurement technique. As a first step, the DTS technique will be extended the application of fiber Bragg grating (FBG) temperature measurements at specific points along the glass fiber. Subsequently a straight segment of a new hybrid cable will be placed in a water channel perpendicular to the flow direction. The Flow will be precisely specified using Particle Image Velocimetry and multiple temperature sensors in the channel and on the cable's sheath will deliver the information for enhanced heat transfer modelling.

Study on Induced Voltage and Circulation Current of Metal Layer in Single-Core Cable of High-Speed Railway Power Transmission Line

The metal shield and metal armor layers of single-core cables on high-speed railroad power penetration lines are usually grounded by common equipment protectors. This grounding method brings a continuous circulating current between the metal shield and metal armor layer compared to the subequipment protection grounding. In order to quantitatively study the circulating current condition of the through line and its influence on the reliability of the railroad power through line, the induced electric potential and circulating current generation mechanism of the single-core cable of the through line and its influencing factors were firstly analyzed in depth. Then, based on the cross-sectional structure of the single-core cable and the location of the traction network and cable in the roadbed section, a traction power supply model was established and simulated for the interlayer-induced potentials and circulating currents due to the two grounding protection methods under no load, single train operation, and heavy load four-train operation of the line. Finally, three actual sections of the Shanghai–Kunming and Nan–Kunming high-speed railroads in China were selected to collect and analyze the loop flow data with no load and with vehicles passing through, and finally the loop flow law of single-core cable for railroad electric through traffic was derived. The analysis shows that when the metal sheath of a single-core cable is grounded by ordinary equipment, the circulating current generated does not exceed 1% of the core current, which meets the relevant safety standards, but the induced voltage in the case of large loads will exceed 50 V safety voltage.

Study on catalytic pyrolysis and combustion characteristics of waste cable sheath with crosslinked polyethylene

Study on catalytic pyrolysis and combustion characteristics of waste cable sheath with crosslinked polyethylene

AC corrosion analysis of the buffer layer in HV corrugated-aluminum sheathed power cables

Here we examine the AC corrosion characteristics of the buffer layer in high voltage corrugated-aluminum sheathed power cables, and analyze the relationship between corrosion and cable failure. Penetration of moisture into the buffer layer, including dampness introduced during manufacture and direct water entry through mechanical damage to the cable sheath, results in AC corrosion and formation of hydrogen and Al(OH)3. On the basis of AC current density spectroscopy, the influences of voltage, moisture content, and pressure on the threshold current density are investigated. The cable structure is considered, and a relationship between the AC corrosion and cable failure is determined. A large ripple depth of the corrugated aluminum promotes a non-uniform circular current distribution. The combination of high moisture content and non-uniform current density results in local high temperatures in the buffer layer that ultimately cause the failure of the power cables.

Diagnostics of a shipboard cable by measuring the dielectric loss tangent

Until now there has not been created a system to assess the residual resource and to predict the probability of shipboard cable failure during its operation by non-destructive methods. Periodic high voltage tests are prescribed by various guidelines. As a result of such diagnostics, the damaged section is identified and the entire cable route is replaced. Obviously, this technology does not prevent an emergency situation, does not provide information about the residual resource, and finally, worsens the properties of an already aged cable exposed to high voltage. Insulation quality control on ships is of great importance and significance. The question arises about the suitability of one or another cable route for further work after long-term operation. That is why the issues of predicting the service life of a cable and assessing its current technical condition are relevant. Modern technologies make it possible to obtain materials with improved characteristics; however, currently rubber-insulated cables are the most common. In this work, diagnostics of the state of a shipboard cable is carried out by determining the dielectric loss tangent of its insulation. This method can be used along with traditional methods for technical audit of shipboard cables, such as testing the hardness of the cable sheath, infrared diagnostics of electrical equipment. In this case, the conclusion about the current state of the cable and the forecast of its service life, in the opinion of the authors, can only be made on the basis of the results of comprehensive diagnostics performed by several methods.

A simple carbon fiber heating wire design method for preventing ice accretion on stay cables

In cold weather, the outer surface of stay cable sheaths easily freezes. When the ambient temperature increases, the ice on the surface melts easily, and there is a risk of falling ice at high altitudes. In this paper, a simple design method is proposed that uses carbon fiber heating wires to prevent the icing of stay cables. Conventional indoor tests and numerical simulations of heat conduction are carried out for a sheath with a single diameter, and the number of heating wires required for different diameter sheaths is obtained. Taking the stay cable sheath of the Qingshan Bridge in Wuhan as an example, when the diameters of the heating wire and the stay cable sheath are 6 mm and 200 mm, respectively, the temperature rise rule of the heating wire, the calibrated heating power and the convective coefficients are obtained through tests and numerical simulations. At an ambient temperature of 4 °C, thread-like ice formed in the arc range of 0.314 m on the surface of the sheath. The critical non-icing temperature required by the heating wire during preheating to ensure that the sheath surface does not freeze is 1.5 °C.

Characteristic Analysis of the Outer Sheath Circulating Current in a Single-Core AC Submarine Cable System

The single-core alternating current (AC) submarine cable can be provided with an outer sheath that is firmly grounded on both ends of the cable. The circulating currents of the outer sheath are generated to be almost as large as the conductor current. The outer sheaths, which have different structures and properties, generate unwanted losses, asymmetric distribution of circulating current, and extra heat in the single-core AC submarine cables. The formation mechanism of the circulating currents in the submarine cable sheath and armoring is analyzed from the perspective of electromagnetic shielding using electromagnetic transient theoretical analysis, simulation calculation, and field experiments. Equations for calculating the circulating currents of the sheath and armoring are proposed, and influences of these relationships that include the different material characteristics of the sheath and armoring are analyzed. The influence factors, which include different levels of magnetic armoring permeability, resistivity, and ground resistance of the outer sheath, can affect the symmetrical distribution of the circulating current in the outer sheaths. We propose using the phase differences to determine the material properties of each metallic section in the submarine cable.

Piperazine/Alkene-Containing Phosphoramide Oligomer for the Intumescent Flame Retardation of EPDM Rubber

Ethylene propylene diene monomer (EPDM) rubber is highly flammable, facing potential fire hazard when it is used as electric cable sheaths, automobile parts, etc. In this work, aiming to reduce fire hazard of EPDM rubber, a piperazine/alkene-containing phosphoramide oligomer poly (2-butene-1,4-dione piperazine fumaroyl phenylphosphonate) (PPFPP) was synthesized and used as charring agent to fabricate intumescent flame retardant with ammonium polyphosphate (APP). When 20 wt% APP/PPFPP (weight ratio: 3:1) was incorporated into EPDM, the flame-retarded EPDM achieved the UL-94 V-0 rating and the limiting oxygen index (LOI) of 27.0%, significantly superior to flame-retarded EPDM consisting of controlled flame retardant PPSPP without alkene and PPFA without phenyl phosphine. In cone calorimeter test, flame retardant consisting of 6.25 wt% PPFPP and 18.75 wt% APP strongly reduced the peak of heat release rate (PHRR) and the peak of smoke production rate (PSPR) of EDPM, diminished approximately by 72% and 60%, respectively. In the case of meeting flame retardancy, mechanical property of flame-retarded EPDM maintained at a high level. Different measurements confirmed that the flame-retardant mechanism of PPFPP is attributed to two aspects. The first one is ascribed to the char-forming action of PPFPP in the presence of alkene and piperazine, playing a barrier role in condensed phase; the second one is due to the gaseous action of phenyl phosphine groups originating from the pyrolysis of PPFPP. In summary, the combination of piperazine and alkene with phenyl phosphine may fabricate an efficient charring agent for the intumescent flame retardation for EPDM.

Reaction to fire of polymethylmethacrylate and polyvinylchloride under reduced oxygen concentrations in a controlled-atmospherecone calorimeter

Electrical cable sheaths are the most abundant fire load in nuclear power plants, mainly in rooms that are kept in under slight pressure. This configuration leads fires to grow in under-ventilated and vitiated conditions. Assessing fire threat involves characterizing the heat released, responsible for fire growth, and the smoke evolved, which may interact with sensitive components in the area. For that purpose, a revisited controlled-atmosphere cone calorimeter has been designed, set up, and coupled to a Fourier transformed infrared spectrometer and an electrical low-pressure impactor to measure simultaneously the evolved gases and aerosols, respectively. This bench-scale apparatus has been first qualified with polymethylmethacrylate. It has second been used to characterize polyvinylchloride cable sheath representative material reaction to fire in under-ventilated and vitiated conditions. It appeared that vitiation in under-ventilated fires lowers the heat release rate and the fuel mass loss rate.

Remediation of Lead Ions from Wastewater Using Magnetic Iron Oxide Nanoadsorbents – A Review

Heavy metal ions removal is a prime concern for pure water and good human health. Lead is one of the most worrisome heavy metal ions. Exposure to lead at trace levels induces neurotoxicity, brain damage, microcytic anemia, kidney damage, hypertension, and toxicity to reproductive organs, and premature birth, miscarriage, and stillbirth for pregnant women. Main anthropogenic sources of lead are mining, smelting, lead acid batteries, use of leaded paint, plastic stabilizers, cable sheathing pigments, and rust inhibitors. Adsorption is the most efficient and effective one. Among different physical chemical and biological procedures are present to mitigate the toxicity of lead ions in water, adsorption is the most efficient and effective one. Amid various nanoadsorbents, magnetic iron oxide nanoparticles are gaining more attention due to their unique physicochemical properties and magnetometric property. This review sheds light on magnetic iron oxide nanoadsorbents and the impact of different functional groups on lead ion adsorption efficiency.

Influence of doping additive on thermophysical and rheological properties of halogen-free polymer composition for cable insulation and sheaths

Introduction. The demand for halogen-free fire-resistant compositions for the manufacture of fire-retardant wires and cables is constantly growing. Problem. Therefore, the creation and further processing of these materials is an urgent problem. Goal. The aim of the article is to study the effect of the doping additive on the thermophysical and rheological properties of halogen-free compositions for power cables with voltage 1 kV with the determination of both the temperatures of phase and structural transformations of polymer compositions. Methodology. Experiments investigating the phase transformations were carried out with the help device of thermogravimetric analysis and differential scanning calorimetry TGA/DSC 1/1100 SF of METTLER TOLEDO company. Rheological studies of polymeric materials were conducted by using the method of capillary viscosimetry in the device IIRT–AM. Results. The influence of the doping additive on the formation of the supramolecular structure of the filled polymer compositions for cable products was determined, that resulted in the temperature increase of the decomposition beginning by 11 °С and the end of decomposition by 7 °С. Originality. The effect of a doping additive on reducing the effective melt viscosity of a polymer composition from 6·104 to 1·104 Pa·s with increasing shear rate has been shown for the first time. The shear rate of the polymer composition containing the doping additive increases from 0.5 to 20 s–1 with increasing shear stress. Practical value. The research results provide an opportunity to reasonably approach the development of effective technological processes for the manufacture of the insulation and sheaths of power cables from halogen-free polymer compositions.

Pemilihan Kabel Instalasi Listrik Untuk Bangunan Gedung Berdasarkan Kualitas Tahanan Isolasi

The building fire in Pontianak was the result of an electrical short circuit or an electric current, namely the connection between a live conductor and a neutral conductor. Where the electrical installation cables used are generally NYM and NYA cables.
 NYM and NYA cables must be of good quality. This is related to the safety of buildings against fire hazards due to short circuits of electrical cables. For this reason, research is needed in the form of measuring cable insulation resistance to ensure the quality and feasibility of several cable brands on the local market in Pontianak.
 Based on the measurement results on the five test samples, each cable NYM 3 x 2.5 mm2, NYM 2 x 2.5 mm2 and NYA 2.5 mm2, it was found that the NYM cable was 3 x 2.5 mm2 (sample A), NYM cable 2 x 2 .5 mm2 (Sample A) and 2.5 mm2 NYA Cable (sample B) have the highest insulation resistance of the cable sheath compared to 4 (four) other samples, namely 25,010 M Ohm (NYM 3 x 2.5 mm2), 25,425 M Ohm ( NYM 2 x 2.5 mm2) and 39,850 M.Ohm (NYA 2.5 mm2). This shows that these cables have a better quality of sheath insulation resistance than others. While the cables that have the smallest sheath insulation resistance are 11,014 M Ohm (Sample B NYM cable 3 x 2.5 mm2), 10,720 M Ohm (Sample B NYM cable 2 x 2.5 mm2) and 21,580 M.Ohm (Sample A NYA 2.5 mm2) cable.

Research on identification of cable sheath defects based on current analysis of cable sheath

Abstract This paper presents a method to detect the different types of defects in cross connected cable sheath in a flat 500kV three leaf high voltage cable system with sheath current as input data. Three different defects are analyzed: the loss of electrical continuity of grounding, the short circuit between metal sheath of cable joint segment and the immersion of junction box. The model of cable system is simulated by theoretical analysis and ATP software. The results obtained by these two methods have achieved good consistency.