High Voltage Power Cables Research Articles

A New Insight into Discharge Ablation Mechanism of Buffer Layer in High Voltage Power Cable

A New Insight into Discharge Ablation Mechanism of Buffer Layer in High Voltage Power Cable

Numerical and experimental analysis of thermal behaviour of high voltage power cable in unfilled ducts

The work addresses the topic of the thermal study of high-voltage power cables installed inside plastic pipes in the absence of filling. The presence of air inside the pipe creates an insulating layer that does not favor heat exchange and makes the calculation of the flow rate more complex, as it is necessary to take into account the thermal phenomena of natural convection and radiation between the surface of the cable and the internal surface of the tube. The numerical model based on the finite element calculation was compared with the experimental results obtained on a simulacrum in which the temperatures on the different layers of the cable were measured. After this validation, some typical installation configurations of single and double energy transport triads were analyzed.

Investigation of cable current carrying capacity improvement and its effects on transmit power between Egypt and Saudi Arabia project

This paper presents an investigation for current carrying capacity improvement of high voltage cable laid in unfavorable regions crowded with groups of high and extra high voltage power cables. A proposed MATLAB program is developed to predict the ampacity of these cables at 220 kV and 500 kV. The cables are laid in various formats and under various laying conditions. Temperature distribution inside cable layers and through soil layers are studied using a finite element model (FEM) with COMSOL software during full load operation. Calculations are based on Neher-McGrath methods in accordance with IEC 60,287. The results are compared with the manufacturer's technical guarantee. Furthermore, this paper presents a proposed cable ampacity calculation that is applied to determine the ideal cross section area for four circuits of 500 kV underground cables that will serve for future power transmission between Saudi Arabia and Egypt.

Alternative Concepts for Extruded Power Cable Insulation: from Thermosets to Thermoplastics.

The most common type of insulation of extruded high-voltage power cables is composed of low-density polyethylene (LDPE), which must be crosslinked to adjust its thermomechanical properties. A major drawback is the need for hazardous curing agents and the release of harmful curing byproducts during cable production, while the thermoset nature complicates reprocessing of the insulation material. This perspective explores recent progress in the development of alternative concepts that allow to avoid byproducts through either click chemistry type curing of polyethylene-based copolymers or the use of polyolefin blends or copolymers, which entirely removes the need for crosslinking. Moreover, polypropylene-based thermoplastic formulations enable the design of insulation materials that can withstand higher cable operating temperatures and facilitate reprocessing by remelting once the cable reaches the end of its lifetime. Finally, polyethylene-based covalent and non-covalent adaptable networks are explored, which may allow to combine the advantages of thermoset and thermoplastic insulation materials in terms of thermomechanical properties and reprocessability.

Enhanced Dielectric Breakdown Property of Polypropylene Based on Mesoscopic Structure Modulation by Crystal Phase Transformation for High Voltage Power Cable Insulation

Enhanced Dielectric Breakdown Property of Polypropylene Based on Mesoscopic Structure Modulation by Crystal Phase Transformation for High Voltage Power Cable Insulation

Revealing the pyrolysis mechanism of polypropylene cable insulation: A combined study of TG‐GC experiments and RMD/DFT simulations

AbstractStyrene grafted polypropylene (PP‐g‐St) is one of the insulating materials for high voltage power cables. However, the process of pyrolysis gas generation in polypropylene cable insulation remains poorly understood. To address this knowledge gap, this study employed a combination of thermogravimetric‐gas chromatography experiments, density functional theory, and reactive molecular dynamics simulations. The experimental findings revealed that the pyrolysis gases primarily consisted of H2, CO, C2H4, and CH4. Higher temperatures were found to increase the yields of H2 and CO. The simulation results indicated that H2 and CO were generated through the rupture of less reactive olefins and radicals, while C2H4 was primarily produced by the rupture of CC bonds in the polypropylene chain. Additionally, CH4 was formed when CH3 groups captured hydrogen from other molecules. By the chain reaction mechanism, we enable the calculation of the activation energy of PP‐g‐St. This study provides a theoretical foundation for understanding the pyrolysis gas generation.

WITHDRAWN: Design of partial discharge measurement model for internal cavities in high voltage power cables

The phenomenon of partial discharge (PD) in power cables can result in insulation degradation and eventual failure if left undetected and unaddressed. As a result, the measurement of PD is key to evaluating the performance of insulation diagnostics in the power cables. This paper presents a PD measurement model for internal cavities in XLPE insulating material for medium voltage power cables. The proposed PD measurement model is designed using the COMSOL Multiphysics software as a finite element analysis (FEA) tool added to MATLAB environment, specifically tailored for power cables. The proposed PD measurement model uses the multiphysics capabilities of COMSOL to simulate the electrical discharges behavior within power cables. The model considers factors such as cable geometry, material properties, cavity size, applied voltage and numerical conditions to accurately capture the PD characteristics. Distributions of both electric potential and electric field were studied before and after occurrence of PD across the internal cavity. According to the results, it has been noticed that the discharge magnitude mainly depends on the cavity diameter; as increasing cavity diameter leads to increasing the magnitude of the measured PD. Moreover, the leakage current magnitude is recorded during the PD event period. The proposed model also enables the evaluation of different cable designs, insulation materials, and operating conditions to optimize cable performance and mitigate PD risks.

An Analysis of the Ampacity and Capital Costs for Underground High Voltage Power Cable Construction Methods

An Analysis of the Ampacity and Capital Costs for Underground High Voltage Power Cable Construction Methods

Grain size effects on the behavior of silicone rubber high voltage power cables using seagull optimization algorithm

<p>High voltage insulation is one of the most important components of electrical power systems. Polymeric materials have lately supplanted ceramic materials as insulating materials due to their low weight, straightforward structure, high mechanical strength, good performance in the presence of pollution, ease of transportation, and ability to enhance voltage. The purpose of this thesis is to add micro and nano-sized aluminum oxide (Al2O3) fillers to silicone rubber (SIR) to enhance its electrical characteristics. Micro Al2O3filler with contents of 10wt%, 20wt%, 30wt%, and 40wt% was combined with nano Al2O3with contents of 1wt%, 3wt%, 5wt%, and 7wt% to create samples of SIRcomposites. The composites’dielectric strength is evaluated in a variety of environments, including dry, wet, low-salt wet, and high-salt wet circumstances. In order to boost the insulator’s dielectric strength under diverse environmental conditions, this research aims to develop a weight ratio composition for such a composite. The ideal concentration of nano or micro Al2O3fillers has been calculated using the whale optimization algorithm (WOA) and seagull optimization algorithm (SOA).</p>

Assessment of potential impact of magnetic fields from a subsea high-voltage DC power cable on migrating green sturgeon, Acipenser medirostris

Empirical evidence suggests that marine animals perceive and orient to local distortions in the earth’s natural magnetic field. Magnetic fields (MFs) generated by electrified underwater cables may produce similar local distortions in the earth’s main field. Concern exists that these distortions may impact migration movements of MF-sensitive animals. The Trans Bay Cable (TBC) is a ± 200-kV, 400-megawatt, 85-km high-voltage direct current transmission line buried through San Francisco Bay (37° 56′ 8.81″ N, 122° 27′ 0.19″ W). Detections of adult green sturgeon implanted with acoustic transmitters were used from six cross-bay receiver arrays from 2006 to 2015 to investigate how inbound and outbound migration movements through lower portions of their route to/from upstream breeding grounds are related to the TBC’s energization status (off/on) and other local environmental variables. Here, we assess how these variables impacted transit success, misdirection from the migration route, transit times, and migration path locations within stretches between the Bay’s mouth and the start of the Sacramento River. Overall, there was varied evidence for any effect on migration behavior associated with cable status (off/on). A higher percentage of inbound fish successfully transited after the cable was energized, but this effect was nonsignificant in models including temperature. Outbound fish took longer to transit after cable energization. Inbound and outbound migration path locations were not significantly influenced by cable energization, but results suggest a potential subtle relationship between energization and both inbound and outbound paths. Overall, additional migration-based studies are needed to investigate the impact of anthropogenic cables on marine species.

Modelling Electro-Mechanical Behaviour of an XLPE Insulation Layer for Hi-Voltage Composite Power Cables: Effect of Voids on Onset of Coalescence

The harshness of the submarine environment represents a serious threat for immersed high voltage power cables, extensively used for offshore wind farms, which in turn are supposed to last for at least 20 years for their total investment to be economically viable. The Crosslinked Polyethylene (XLPE) used for the insulating layer of the cables may suffer different degradation phenomena, leading to unexpected breakdowns and rises in costs. In this work, numerical simulations have been developed to study the mechanisms by which micrometric pores inside XLPE can enlarge and coalesce (namely, water treeing) when the insulation is subjected to the intense electric field generated by hi-voltage wires. The study aim is to predict material plasticization next to voids, which is supposed to represent the onset of coalescence of neighboring pores. A microscale-level finite element coupled electro-mechanics model has been developed to describe the interactions between the intense electric fields and the subsequent Maxwell stresses in a dielectric. The roles of different influencing parameters such as distance, relative volumes, and the shape of two neighboring voids in a representative unit volume are considered. Finally, the behavior of a generic microstructure characterized by randomly distributed voids immersed in an electric field is simulated.

ONLINE PARTIAL DISCHARGE MEASUREMENT FOR CONDITION-BASED MAINTENANCE OF HV POWER CABLES IN RAILWAY INFRASTRUCTURE

Partial discharge (PD) measurement as one of well-known method to evaluate the condition of high voltage (HV) power cables has been studied over many decades. Cable insulation failure could result in a power outage, which could then cause a loss of service in the transportation system and even dangerous events like fire accidents. It is of a great interest to railway infrastructure operators to monitor and identify the cable faults before any possible accident occurs. The paper focuses on the diagnostic problem to detect the HV cable fault based on the Phase Resolved Partial Discharge (PRPD) patterns. Classification models, such as Random Forest and Convolutional Neural Network, are considered to classify the pattern of PRPD based on the mostly occurring PD types in HV cables, such as corona, surface, and void patterns. Experiments are performed and the PRPD data from the experiments are collected. The optimal model is applied in the online monitoring program which will be used continuously to evaluate the cable condition and arrange the optimal schedule for maintenance. According to the analysis, both algorithm perform well in the PRPD pattern categorization, with accuracy up to 83.45%. This indicates that due to the more effective behavior, PD assessment with PD sensors is preferable.

Feature extraction based on time-series topological analysis for the partial discharge pattern recognition of high-voltage power cables

In the partial discharge (PD) pattern recognition of power cables, the existing time–frequency features often exert an impact on recognition accuracy because of insufficient discrimination. A novel PD feature extraction and identification method on the basis of time-series topological data analysis (TDA) was proposed in this paper. Firstly, original PD sequence was reconstructed as point cloud in phase space based on optimized symbolic entropy. Then, a PD topological space is constituted with point cloud to extract its persistent homology features. On this basis, persistence diagrams and barcodes were calculated and visually expressed as Betty curves. Finally, Betty curves were input into an optimized 1D convolution neural network (1D-CNN) model to recognize four typical PD patterns and carry out comparison experiments. The visualization produced by t-distributed stochastic neighbor embedding (t-SNE) shows that TDA features possess significant discrimination, experiencing an increase of 11.25% in the overall recognition accuracy and reaching 98.00% compared with original PD sequence and time–frequency features. Meanwhile, the computation cost of the proposed algorithm is optimized within the permissible range for real-time applications.

Comparison of On-Line Partial Discharge Detection Techniques for High Voltage Power Cable Joints and Terminations

Cable joints and terminations play a vital role in providing dependable electrical connection, mechanical support and physical safeguard. These provide electrical stress control to shielded power cables. Despite their usefulness, they suffer from partial discharges (PD) because of enhanced voltage stress, moisture ingress and poor workmanship (during installation). Therefore, it is necessary to undertake on-line PD detection to determine their state. Some of these techniques are capacitive coupler (CC); acoustic emission (AE); and high frequency current transducer (HFCT). This article presents a literature review of these techniques based on the cost, availability, and applicability. The comparative analysis is also provided on location of their sensors, quantification and detection ability. The CC technique involves the quantification of the coupler sensor input measured in mV/pC by realizing the time of flight between two sensors for which the results are used to estimate location of the PD. Meanwhile, the AE technique has an advantage of high immunity to electrical noise, with a caveat that acoustic signals are highly attenuated within the cable joints. Additionally, the combination of the acoustic sensors and PD electrical couplers can be used to discriminate PDs from electrical noise. The HFCT has two methods – with demonising (HFCT-WiD) and without demonising (HFCT-WoD). The HFCT-WiD technique can significantly reduce the sensor’s detection sensitivity due to its high value of noise to signal ratio (NSR). Comparatively, the HFCT has the best results of quantification and detection ability for PDs among all three techniques investigated. However, in places where electrical noise is severe, PD activities may be detected effectively with AE technique. Further work is needed to statistically map these methods and establish their correlation with experimental data.

Study on high-temperature and high-voltage insulation characteristics of polypropylene blend with highly packed elastomeric domains for power cable applications

In this paper, we report the high-temperature and high-voltage (HV) insulation characteristics of the polypropylene (PP) blend with highly packed elastomeric domains that showed excellent mechanical toughness in our previous study to find its suitability as insulation material for power cable applications. The main focus lies on tensile properties with thermal aging, thermomechanical behavior corresponding to the thermal transition, high-temperature volume resistivity and DC dielectric strength, and space charge accumulation behavior of the PP blend in comparison to the crosslinked polyethylene (XLPE). Our PP blend having low elastic modulus of approximately 266.9 MPa exhibited high tensile strength and elongation at break, and high-temperature stability as well. Using this PP blend, not only good HV insulating performances in volume resistivity and DC breakdown strength (BDS) were obtained similar to XLPE, but also adequate values were obtained at high temperature, even at 110 °C, which was not possible with XLPE. However, there was space charge accumulation and electric field distortion in the PP blend like XLPE, which needs to be suppressed. Therefore, our PP blend is expected to have the potential to replace existing XLPE as insulation materials for future HV power cables.

PCB-Based Planar Inductive Loops for Partial Discharges Detection in Power Cables

Partial discharge (PD) diagnosis tests, including detecting, locating, and identifying, are used to trace defects or faults and assess the degree of aging in order to monitor the insulation condition of medium- and high-voltage power cables. In this context, an experimental evaluation of three different printed circuit board (PCB)-based inductive sensor topologies, with spiral, non-spiral, and meander shapes, is performed. The aim is to assess their capabilities for PD detection along a transmission power cable. First, simulation and experimental characterization are carried out to determine the equivalent electrical circuit and the quality factor of the three sensors. PD activity was studied in the lab on a 10-m-long defective MVAC cable. The three PCB-based sensors were tested in three different positions: directly on the defective cable (P1), at a separation distance of 10 cm to 3 m (P2), and on the ground line (P3). For the three positions, all sensors' outputs present a damped sine wave signal with similar frequencies and durations. Experimental results showed that the best sensitivity was given by the non-spiral inductor, with a peak voltage of around 500 mV in P1, 428 mV in P2, and 45 mV in P3, while the meander sensor had the lowest values, which were approximately 80 mV in P1. The frequency spectrum bandwidth of all sensors was between 10 MHz and 45 MHz. The high sensitivity of the non-spiral inductor could be associated with its interesting properties in terms of quality factor and SFR, which are due to its very low resistivity. To benchmark the performance of the designed three-loop sensors, a comparison with a commercial high-frequency current transformer (HFCT) is also made.

Polystyrene: A Self-Dispersing, Ultralow Loading Additive for Improving the Breakdown Strength of Polypropylene for High Voltage Power Cable Applications

Voltage stabilizers (VSs) with benzene derivatives have received great interest as high-performance additives for improving the electrical durability of polypropylene (PP)-based insulation materials for high voltage (HV) power cable applications. In this work, atactic polystyrene (aPS) was first used as a thermoplastic VS (TVS) to efficiently dope the benzene units into isotactic PP (iPP). The aPS TVS was incorporated in the iPP matrix through melt-mixing, and the domain size of immiscible aPS decreased with the decrease of aPS content. The smaller amount of aPS doping increased the direct current (DC) breakdown strength (BDS) of iPP, even at ultralow loading levels below 0.01 phr. The enhancement ratio of the BDS value of iPP with 0.001 phr of aPS was higher compared to the results obtained for other types of additives reported in the previous literature.

Fiber-Optic Sensors (FOS) for Smart High Voltage Composite Cables-Numerical Simulation of Multi-Parameter Bending Effects Generated by Irregular Seabed Topography.

Offshore renewable energy requires reliable high-voltage electric power cables to transport electricity to onshore stations. These power cables are critical infrastructures that are shipped to deep seas through shipping and handling operations and, once mounted, must then evolve in extreme conditions (sea, salt, wind, water-pressure, seabed topography, etc.). All of these operations and working conditions can lead to yielding of copper conductors, often resulting in electric shutdown. Indeed, copper is an excellent electric conductor (conductivity), but its mechanical properties are very poor. If any negligence occurs during the shipping and/or handling operations, copper can undergo plasticity, with effects on both mechanical and electric properties. It is therefore of prime importance to establish a reliable structural health-monitoring (SHM) technique that will enable the continuous recording of copper strain and temperature along a cable, and this has been proven using fiber-optic (FOS) sensors, when the phase is under tensile loading. In this prospective article, the scope is to maintain previous simulations and thus show that by the judicious placement of FOS, one can monitor strain and temperature within cables that are submitted to a bending. This article does not aim to deal directly with the case of a cable that undergoes bending on sloppy areas in seabeds. The idea behind the work is to suggest a concept for the use of embedded fiber-optic sensors and to think about all of what remains to be done as research in order to further suggest this technology to cable manufacturers.

Analysis for metal sheath corrosion rate in AC high voltage power cable

Reliable power transmission requires the safe operation of high-voltage cable. A number of high-voltage cable failures caused by aluminium sheath corrosion has been reported these years. However, neither discussion on factors influencing corrosion rate nor specification describing corrosion inhibiting method has been presented. Thus, it is crucial to address the research gap in evaluating corrosion rate of aluminium sheath in various corrosive environments. Here, the effect of chlorides on aluminium sheath corrosion is analyzed. Using scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), the corroded surface is investigated. Titration experiment is performed to quantify the chlorides content in buffer layer of cable. Polarization curves are employed to analyze the corrosion rate of aluminium sheath in different chlorides content environment. Surface analysis result shows that chlorine-rich phase can be observed on the corroded surface. Titration experiment result reveals that buffer layer used in high voltage cable is one of the sources of chlorides content which varies from 0.7 to 4.2 wt%. Finally, polarization curve shows that when chloride content increases from 0.6 to 1.8 wt%, the pitting potential left shifts from −0.689 to −0.742 V. The corrosion resistance of aluminium sheath deteriorates significantly with the increase of chlorides content.

A Comparison of Electrical Breakdown Models for Polyethylene Nanocomposites

The development of direct current high-voltage power cables requires insulating materials having excellent electrically insulation properties. Experiments show that appropriate nanodoping can improve the breakdown strength of polyethylene (PE) nanocomposites. Research indicates that traps, free volumes, and molecular displacement are key factors affecting the breakdown strength. This study comprehensively considered the space charge transport, electron energy gain, and molecular chain long-distance movement during the electrical breakdown process. In addition, we established three simulation models focusing on the electric field distortion due to space charges captured by traps, the energy gain of mobile electrons in free volumes, the free volume expansion caused by long-distance movement of molecular chains under the Coulomb force, and the energy gained by the electrons moving in the enlarged free volumes. The three simulation models considered the electrical breakdown modulated by space charges, with a maximum electric field criterion and a maximum electron energy criterion, and the electrical breakdown modulated by the molecular displacement (EBMD), with a maximum electron energy criterion. These three models were utilized to simulate the breakdown strength dependent on the nanofiller content of PE nanocomposites. The simulation results of the EBMD model coincided best with the experimental results. It was revealed that the breakdown electric field of PE nanodielectrics is improved synergistically by both the strong trapping effect of traps and the strong binding effect of molecular chains in the interfacial regions.