Cable Insulation Layer Research Articles

Transient Temperature Distribution of Cable Insulation Layer and Finite Element Analysis

To address the limitations of existing technologies in cable temperature rise monitoring and early warning systems, this paper presents an advanced analytical method that provides accurate cable temperature monitoring and early warning mechanisms for power systems. First, we established a transient temperature model of the cable insulation layer to accurately predict its radial temperature distribution at any given time. The temperature evolution of the insulation layer over time was then calculated using the finite element method. The effectiveness of the proposed model was verified through simulated temperature rise tests at different current levels. Simulation results indicate that the model can accurately simulate the temporal variation of cable temperature under specific current and environmental conditions. Additionally, it precisely models the radial temperature distribution of the cable, identifying hotspot locations. This model not only elucidates the dynamic relationship between current and insulation characteristics but also provides a basis for cable hot spot warnings. Its practical application can effectively prevent cable overheating damage, demonstrating significant practical value.

Floating photovoltaic systems: photovoltaic cable submersion testing and potential impacts.

Floating photovoltaics (FPV) is an emerging technology that is gaining attention worldwide. However, little information is still available on its possible impacts in the aquatic ecosystems, as well as on the durability of its components. Therefore, this work intends to provide a contribution to this field, analysing possible obstacles that can compromise the performance of this technology, adding to an increase of its reliability and assessing possible impacts.The problem under study is related to the potential submersion of photovoltaic cables, that can lead to a degradation of its electrical insulation capabilities and, consequently, higher energy production losses and water contamination. In the present study, the submersion of photovoltaic cables (with two different insulation materials) in freshwater and artificial seawater was tested, in order to replicate real life conditions, when FPV systems are located in reservoirs or in the marine environment. Electrical insulation tests were carried out weekly to assess possible cable degradation, the physical-chemical characteristics of the water were also periodically monitored, complemented by analysis to detect traces of copper and microplastics in the water. The results showed that the submersion of photovoltaic cables with rubber sheath in saltwater can lead to a cable accelerated degradation, with reduction of its electrical insulation and, consequently, copper release into the aquatic environment. The test results pointed a probable relationship between submersion of cables with rubber outer shell and water freezing temperatures and the occurrence of accelerated degradation of the cable insulation layer. Reduced insulation resistance values were measured in this cable type after the occurrence of such temperatures, both in salt and freshwater, the cable presented visible exterior degradation signs. For this case copper residues were detected in the water.

Electrical properties of MAH-g-PP modified PP/SEBS matrix semi-conductive composite materials

Polypropylene (PP) becomes a superior candidate material for new environmental-friendly cable insulation layer with its excellent heat resistance, electrical properties and degradability. At present, most of studies focus on the insulation layer of PP cable. However, there are few studies on semi-conductive shielding layer of PP cable which match its insulation layer. In this paper, polypropylene (PP)/styrene ethylene butylene styrene (SEBS) is adopted as matrix of PP cable semi-conductive layer to matching its insulation layer. Meanwhile, Maleic anhydride grafted polypropylene (MAH-g-PP) is used to cooperatively improve the compatibility between PP and SEBS. The physicochemical properties, space charge injection properties and compatibility of semi-conductive composites with different CB and MAH-g-PP contents is studied by combining experiment and simulation methods. The experimental results show that the surface roughness of the semi-conductive layer and the space charge inside the insulation layer decrease first and then increase with the increase of CB addition. Among them, the two parameters of 25 phr CB semi-conductive layer is the lowest, respectively 13.98 nm and 2.25 × 10−8C. These two parameters are significantly reduced after the addition of compatibilizer MAH-g-PP, which decreased by 29.47 % and 62.22 %, respectively. The simulation results show that the Flory-Huggins interaction parameters (χ) of MAH-g-PP with PP and SEBS are −73.3 and −45.2, respectively, which are 236.24 % and 107.34 % lower than those of PP/SEBS. The χ value of MAH-g-PP/CB is 8.20, which is 33.27 % and 9.59 % lower than CB/PP and CB/SEBS, respectively. It shows that MAH-g-PP can effectively improve the compatibility of matrix and filler. This work has important guiding significance for the research of semi-conductive layer formulation of PP cable.

High throughput synthesis of SiO2 microspheres enhancing dielectric properties of quartz fibers insulation composites for high temperature resistant communication cable

The development of the digital society has led to an urgent demand for high-temperature-resistant, low-dielectric cable insulation materials. In order to meet the stable high temperature service performance, it is necessary to use inorganic materials instead of the traditional organic insulating materials as the cable insulation layer. Silicon dioxide (SiO2) as a widely used inorganic dielectric material has great potential for application, and quartz fiber is another wave-transparent material with good dielectric properties. The combination of SiO2 and quartz fiber can provide a feasible path for pure inorganic composite insulation materials. In this work, the high-throughput (>50 g) synthesis of SiO2 was investigated to explore the factors affecting the dielectric properties. The effects of different quartz fiber composite amounts and sintering temperatures on the dielectric properties of the composites were investigated by testing the dielectric properties of the composite powders after pressing. The composite powders doped with 20 wt% quartz fibers at 600 °C sintering temperature were found to have better dielectric properties with dielectric constant of 2.48 and dielectric loss of 0.0109 at 20 M Hz. Furthermore, the composite powders were filled into the cables and measured for electrical properties by a network analyzer. And dielectric properties of the cables preliminarily meet the performance requirements for the applications of high temperature (900 °C) radio frequency (RF) communication cables with dielectric constant of 1.731 and insertion loss of 2.02 dB at 18 G Hz. Therefore, this inorganic composite material can be used as the insulation layer for RF high-temperature-resistant communication cables for aerospace, nuclear power plants and energy fields.

Design of voltage stabilizers for high breakdown strength materials

AbstractHigh breakdown strength material in the cable insulation layer is a key enabler for high voltage power transmission. In this work, we seek to design high‐performance voltage stabilizers to be compounded into polyethylene to improve its breakdown strength. We hypothesize that electron affinity (EA) and HOMO‐LUMO gap are two key factors that affect the performance of voltage stabilizers. To achieve larger EA and smaller HOMO‐LUMO gap, we propose to use aromatic molecules decorated with electron acceptors and donors. A search of an internal chemical database narrows down to 529 molecules using structure, ClogP, and H‐phrases (hazard statement) as criteria. The EA and HOMO‐LUMO gap of these molecules are then calculated and experiments are carried out to measure the performance of 20 molecules. The performance improvement does not show a significant correlation with either EA or HOMO‐LUMO gap. However, the best performers have an EA of 1.3–2.3 eV and HOMO‐LUMO gap of 3.2–5.2 eV. The experimental study shows that adding side groups to voltage stabilizers will typically degrade their performance because side groups will generally increase the distance between the HOMO‐LUMO orbitals and polyethylene backbone, and therefore decrease the electron/hole tunneling effectiveness.

Research on Cable Insulation Layer Defect Detection Based on Terahertz Technology

The insulation layer of a cable plays a very important role in protecting the cable. If defects such as voids and detachment occur in the insulation layer of the cable, it can lead to a short circuit in the cable and cause a fire. In this article, a new insulation layer detection method is proposed, which uses terahertz equipment to detect defects in cables and obtain terahertz images with defects. However, some defect images are relatively blurry. Morphological algorithms are used to denoise and enhance the blurry images to obtain high-quality defect images to determine the location and size of defects. Terahertz technology has become a new method for detecting defects in cable insulation layers and is increasingly widely used.

Defect detection of composite materials for cable insulation layer based on terahertz

Hidden defects can seriously affect the insulation performance of cables and pose safety hazards. In this article, a novel Non-Destructive evaluation technique for insulation materials based on terahertz time-domain spectroscopy technology is proposed. Firstly, terahertz time-domain spectroscopy technology was used to perform reflective scanning on insulation materials. Various imaging algorithms were used to image terahertz defects. The results showed that the maximum imaging and peak to peak time imaging were effective. At the same time, bilateral filtering was used to process terahertz defect images. The results showed that bilateral filtering not only filtered out noise in terahertz images, but also retained edge details. Terahertz time-domain spectroscopy technology offers a fresh approach for detecting cable insulation material defects non-destructively, and finds application in various electrical environment inspections.

Defect detection and identification for aircraft cable insulation layer based on deep forest

Due to the special internal environment of aircraft, cable damage is inevitable, which usually starts from insulation layer defects and may cause major economic losses, and even seriously threaten the life of people on board. According to the above issue, a defect detection system for aircraft cable insulation layer based on ultrasonic guided waves (UGWs) is built in this paper. In order to ensure the complete coupling between the sensor and the insulation layer of the aircraft cable, the macro fiber composite (MFC) flexible sensor is employed in the system. Both simulation and experimental results show that this method can simultaneously monitor four different types (abrasion, cut, semi-stripping and full-stripping) of cable insulation layer defects at different locations on the same cable. The reflection signals of different types of defects are extremely similar and difficult to distinguish directly. In this paper, a classification method for four types of defects based on the deep forest method is proposed. This method requires a small sample size, and the classification performance is not affected by network structure and parameters. The recognition accuracy can reach 100%, avoiding the problem of traditional deep learning classification relying on a large number of samples and requiring parameter adjustment. The proposed method in this paper is proven to be able to effectively carry out online monitoring and accurately classify defect types, which has guiding significance for aircraft maintenance personnel to take corresponding measures in time.

Abnormal line loss identification system of low voltage distribution network based on HPLC communication technology

AbstractPower cable is mainly responsible for the transmission and distribution of electric energy in the power grid. The performance of a power cable greatly affects the reliability and security of the power supply. In order to solve the problem of cable aging caused by long‐term operation and various internal and external factors, this paper proposes an abnormal line loss identification method for a low‐voltage distribution network station area, aiming at focusing on the monitoring of cable aging. The transmission characteristic model based on the transmission line theory and the dielectric constant model of the aging cable insulation layer is established, and the internal relationship between the transmission characteristic and the aging characteristic is analyzed. The characteristic extraction algorithm is used to extract the characteristics of the transmission characteristic curve. Through simulation analysis, for the abnormal line loss fault, the location accuracy of different fault locations is basically at the level of 0.1–0.3%. The simulation of local defects in the cable shows that the change of material dielectric constant is more clear for the characterization of cable aging. The monitoring method in this paper is helpful to provide the relevant basis for the line maintenance plan and the operation strategy of the power grid and is of great significance to ensure the safe and stable operation of the power grid.

Floating photovoltaic systems: photovoltaic cable submersion testing and potential impacts

Background: Floating photovoltaics (FPV) is an emerging technology that is gaining attention worldwide. However, little information is still available on its possible impacts in the aquatic ecosystems, as well as on the durability of its components. Therefore, this work intends to provide a contribution to this field, analysing possible obstacles that can compromise the performance of this technology, adding to an increase of its reliability and assessing possible impacts. The problem under study is related to the potential submersion of photovoltaic cables, that can lead to a degradation of its electrical insulation capabilities and, consequently, higher energy production losses and water contamination. Methods: In the present study, the submersion of photovoltaic cables (with two different insulation materials) in freshwater and artificial seawater was tested, in order to replicate real life conditions, when FPV systems are located in reservoirs or in the marine environment. Electrical insulation tests were carried out weekly to assess possible cable degradation, the physical-chemical characteristics of the water were also periodically monitored, complemented by analysis to detect traces of copper and microplastics in the water. Results: The results showed that the submersion of photovoltaic cables with rubber sheath in saltwater can lead to a cable accelerated degradation, with reduction of its electrical insulation and, consequently, copper release into the aquatic environment. Conclusions: The test results pointed a probable relationship between submersion of cables with rubber outer shell and water freezing temperatures and the occurrence of accelerated degradation of the cable insulation layer. Reduced insulation resistance values were measured in this cable type after the occurrence of such temperatures, both in salt and freshwater, the cable presented visible exterior degradation signs. For this case copper residues were detected in the water.

The Lifetime Prediction and Insulation Failure Mechanism of XLPE for High-Voltage Cable

The performance parameters and service life of the insulation layer of high-voltage cables are the key to ensure safe cable operation. Through extracting the mechanical parameters of high voltage cable insulation layer under different thermal aging temperatures, a normal linear regression model is established to predict the service life of high voltage cables. Meanwhile, the physicochemical characteristics such as microscopic morphology and molecular structure changes of the cable insulation layer are analyzed, the dielectric properties and breakdown field strength under ac condition are tested and the macroscopic electrical properties of the insulation layer are studied, and the insulation failure mechanism is further analyzed. The experimental results show that the elongation at break retention rate of cross-linked polyethylene (XLPE) increases slowly with the aging time, and then decreases rapidly when it reaches 50% of the initial elongation at break retention rate. The normal linear regression prediction model is established based on the Arrhenius formula, and it can be obtained the life endpoint of XLPE high voltage cable about 65 years at an operating temperature of 70 °C. Further analysis, under the action of heat and oxygen, the crystal zone structure of cable insulation is seriously damaged, and the carbonyl index is significantly increased. Accordingly, when the aging failure point is reached, the dielectric permittivity and dielectric loss of insulation are significantly increased, and the breakdown performance is significantly decreased. The work has an important guiding significance for insulation condition assessment and life prediction of high voltage cable.

Interface thermal resistance of micron-thin film

The utilize of multilayer stacked structure dielectric is very common in electrical engineering, such as thin film capacitor wound by multilayer dielectric, and oil paper cable insulation layer formed by multilayer oil paper winding. Interface thermal resistance between dielectric layers are crucial thermo-physical parameters, which are very important for the thermal management of electric devices to improve the operating stability. However, there are some difficulties in precisely measuring thermal resistance parameters between micron-thin films by conventional ways. In this paper, a novel method is proposed for measuring thermal resistance parameters between films based on the thermal pulse method, which is normally used for mapping space charge or electric field distribution. The sample in this paper is of a multilayer structure containing at least one insulating dielectric film. The parameters of the interface thermal resistance of the multilayer structure are obtained by simulating and analyzing the thermal response current characteristics of the dielectric film. To study the characteristics of interface thermal resistance, several different thin film interfaces were designed by changing the type of thermal interface materials and the roughness of the contact surface. The obtained data of the interface thermal resistance show well consistence with the theoretical expectation.

Influence of Thermal Aging on Dielectric Properties of High Voltage Cable Insulation Layer

Thermal aging is one of the main reasons for the degradation of insulation properties of high voltage cable. Dielectric properties and breakdown strength are important parameters to reflect the insulation performance of the cable insulation materials. In the work, the influence of thermal aging on dielectric and breakdown performance of the cable insulation layer was studied. Firstly, XLPE cable insulation samples were prepared and the thermal aging treatment was carried out. Secondly, the microstructure and molecular structure of XLPE samples under different thermal aging time were analyzed. The dielectric properties and breakdown characteristics of XLPE samples under different thermal aging times were characterized in macro aspect. Finally, the effects of different temperatures on the molecular microstructure of XLPE were studied. The results show that with the extension of thermal aging time, the microstructure of XLPE molecule is destroyed, the macromolecular chain is gradually cleaved, and the carbonyl absorption intensity increases. At power frequency, the breakdown strength decreases from 75.37 kV/mm to 62.18 kV/mm, the relative permittivity increases from 2.44 to 2.51, and the dielectric loss increases from 1.47 × 10−4 to 3.10 × 10−3. The free volume rate of XLPE molecules increases with the increasing temperature, and the mean square displacement gradually increases. The work has good guiding significance for the safe operation and condition assessment of high-voltage cables.

Identification of XLPE cable insulation defects based on deep learning

The insulation aging of cross-linked polyethylene (XLPE) cables is the main reason for the reduction in cable life. There is currently a lack of rapid and effective methods for detecting cable insulation defects in power-related sectors. To this end, this paper presents a method for identifying insulation defects in XLPE cables based on deep learning algorithms. First, the principle of the harmonic method for detecting cable insulation defects is introduced. Second, the ANSYS software is used to simulate the cable insulation layer containing bubbles, protrusions, and water tree defects, and the effects of each type of defect on the magnetic field strength and eddy loss current of the cable insulation layer are analyzed. Then, a total of 10 characteristic quantities of the total harmonic content and 2nd to 10th harmonic currents are constructed to establish a database of cable insulation defects. Finally, the deep learning algorithm, long short-term memory (LSTM), is used to accurately identify the types of insulation defects in cables. The results indicate that the LSTM algorithm can effectively diagnose and identify insulation defects in cables with an accuracy of 95.83%.

Effect of space charge accumulation on electric field distribution of high voltage cable

Space charge location and amount are key factors affecting the local insulation performance. This work focuses on the effect of space charge distribution and charges accumulation amount on the electric field distribution of HVDC cables. In the experiment, the dielectric properties and the conductivity properties of the specimen from the operating cable are measured. The simulation model of the electric field of HVDC cables is established, and the effect of charge accumulation on the electric field in the insulation layer are calculated. The experimental results indicate that the dielectric constant of the XLPE cable insulation layer gradually decreases with temperature, from 2.43 at room temperature to 2.21 at 90°C. Conductivity increases with temperature from 5.23×10-15S/m at room temperature to 1.58×10-12S/m at 90°C. The experimental parameters are brought into the simulation model and the calculation results show that the maximum electric field of the insulation layer increases from 24.5 kV/mm to 26.2 kV/mm when the positive charges accumulate between the insulation layer and the inner semi-conductive layer, and it decreases to 22.8 kV/mm when the negative charge accumulate.

Design and Performance Tests of a Fault Current-Limiting-Type Tri-Axial HTS Cable Prototype

Current-limiting superconducting cable uses the quench resistance of superconductor under short-circuit current to improve the short-circuit impedance of the system. In this paper, the design of current-limiting 10 kV three-phase tri-axial superconducting cable is studied. The design methods of cable conductor layer, insulation layer and current-limiting characteristics are given, and one 5 m-long sample is fabricated for testing. The sample is made of stainless-steel-reinforced yttrium barium copper oxide (YBCO) tape, with an expected rated current of 2.5 kA and rated voltage of 10 kV. The test results show that the designed cable can transmit a maximum AC current of 3.0 kA at 77 K. The cable has passed the power frequency withstand voltage, partial discharge and lightning impulse tests. The current limiting characteristics under the action of DC pulse current show that the cable can quickly quench and produce resistance, and the corresponding equivalent resistance value also changes along with current amplitude and duration.

Field Strength Simulation of Typical Defects in XLPE Cable

Crosslinked polyethylene (XLPE) cables are now widely used in power transmission. Due to various factors, XLPE cables are unavoidable to produce defects during installation, transportation and use. These defects can easily cause partial discharge and even lead to cable breakdown accidents, which can cause great losses. [1] In this paper, three typical defects in XLPE cables are studied: air gap defect inside XLPE insulation, metal spike defect on the surface of insulation layer and metal particle defect on the main insulation surface. Electric field simulation is carried out by COMSOL finite element software. Three corresponding cable models under 132kV DC voltage are established, and the simulation analysis of electric field strength is carried out. The field strength distributions for different defects are obtained. The results show that the overall electric field strength of the insulation defect decreases with the distance from the surface of the cable insulation layer. However, the distortion of the electric field strength at the defect is different according to the location and size of the insulation defect. It needs to be simulated under different conditions.

Influence of bubbles on electric field distribution of butt‐gaps in superconducting cable insulation layer

Superconducting energy pipeline (SEP) is a new type of electrical energy transmission. It contains high-temperature superconducting cables and liquefied natural gas pipelines and can simultaneously transmit electricity and liquefied natural gas (LNG). However, when the superconducting tapes in the superconducting cables in SEP quench and generate heat, bubbles will generate in the butt-gaps of the insulation layer of superconducting cables, which can reduce the insulation strength of the cables significantly. In addition, the effects of bubbles in the butt-gap of the insulation layer on the insulation properties of the superconducting cables are unknown. The objective here is to obtain the influences of bubbles in the insulation layer of superconducting cables in capacitive field, transitional field, and resistive field. Simulation results show that: Compared with the absence of bubbles, the big bubbles can increase the capacitive field strength of the PP film, the butt-gap, and the kraft by 37.54%, 30.89%, and 18.5%, and increase the transition time from the capacitive field to the resistive field, but has almost no effect on the butt-gap in the resistive field.

RLS Impedance Intelligence Control Algorithm for Wire Peeler of Robot in Complex Power Networks

Considering the wire core which is easily damaged because of the instability of the power distribution robot during the process of peeling the insulation layer, we have proposed a cutting force tracking control algorithm based on impedance control that is suitable for the end peeling instrument. At present, the task requirement of sudden changes about environment stiffness cannot be accomplished by many impedance control approaches due to the complexity of working environment stiffness about power distribution robot; then, the Recursive Least Square (RLS) method was introduced into the impedance control algorithm to identify the cable insulation layer and cable core stiffness online to achieve accurate and stable tracking of the cutting force. Furthermore, the impedance control of peeling cable insulation layer and the proposed RLS method were simulated and tested contrastively, and the high-voltage cable peeling experiment was performed. The results of simulation and experiment showed that the force control algorithm based on RLS parameter identification still has good force tracking performance during the environment stiffness changes suddenly, and the steady-state error approaches zero, demonstrating the feasibility and effectiveness of the RLS impedance control algorithm, which has important practical significance for improving power distribution efficiency.

Structural Health Monitoring for Cables with Insulation Layer by Envelope Analysis Based on Ultrasonic Guided Waves

Cables play an important role in industries and their insulation layer may experience aging problems, which can lead to serious consequences such as fire. Therefore, monitoring the condition of the cable insulation layer can effectively avoid accidents. In this paper, a structural health monitoring method for cables with insulation layer is proposed, which is based on ultrasonic guided waves (UGWs). In the method the UGWs are generated by MFC transducers and do not affect the normal operation of the cables. When UGWs propagating in the cable encounter defects, the reflected signals appear and can be acquired by the measurement system. The signal received by MFC transducers is processed to extract the characteristics. According to the envelope of received signals, it can be judged whether the current cable insulation is defective. In the experiment, cables in different conditions are tested and defects are successfully detected.