Power Cable System Research Articles

Aging Detection of 110 kV XLPE Cable for a CFETR Power Supply System Based on Deep Neural Network

To detect the aging of power cables in the TOKAMAK power supply systems, this paper proposed a deep neural network diagnosis model and algorithm for power cable aging, based on logistic regression according to the characteristics of different high-order harmonics generated by different aging parts of the power cable. The experimental results showed that the model has high diagnostic accuracy, and the average error is only 2.35%. The method proposed in this paper has certain application potential in the CFETR power cable auxiliary monitoring system.

A turnkey gaseous helium-cooled superconducting CORC® dc power cable with integrated current leads

High-temperature superconducting (HTS) direct current (dc) power cable systems, capable of delivering power exceeding 10 MW while being cooled with cryogenic helium gas, have been developed for applications on naval electric ships, electric aircraft and in data centers. Current injection from room temperature into the superconducting power cable causes by far the greatest heat load to the cryogenic system. Efficient current leads with integrated helium gas heat exchangers were developed to inject a current exceeding 1 kA from room temperature into a superconducting Conductor on Round Core (CORC®) power cable, without the need for liquid nitrogen pre-cooling. A 2 m long single-pole CORC® power cable system that included current leads was cooled using a Stirling cryocooler with a closed-loop helium gas circulation system. The turnkey power cable system allowed cool down from room temperature to its operating temperature of 60 K–70 K within 5 h, after which continuous operation at 1.2 kA was demonstrated. The successful development and demonstration of a CORC® power cable with current leads containing integrated helium gas heat exchangers enables widespread implementation of HTS MW-class, high current density superconducting dc power cables in many applications with constrained space that require a power dense solution.

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.

A Novel Dampness Diagnosis Method for Distribution Power Cables Based on Time-Frequency Domain Conversion

Dampness invasion of power cable joints may lead to cable insulation degradation gradually. Once the cable joint is severely damp, it rapidly leads to breakdown failure for the power cable insulation system and finally results in catastrophic cable accidents. To avoid power outages, it is of great significance to diagnose cable joints with severe dampness defects. Existing methods have certain limitations. In this article, a novel time-frequency domain conversion method for determining cable joints with severe dampness defects is proposed. For this method, the cable joint is first located by applying the conventional frequency domain reflectometry (FDR) technology. Then, the time domain waveform at the cable joint is obtained based on the proposed time-frequency domain conversion algorithm. Finally, the cable joint with severe dampness defect can be distinguished by judging the polarities of the time domain spectrum at the cable joint. To verify the effectiveness of the proposed method, simulations and experiments are performed with comparisons with the conventional FDR method. Simulation and field detected results prove that the proposed method can effectively distinguish cable joints with severe dampness defects.

Barrier effect on electrical tree growth characteristics in silicone rubber

Reliable power cable systems are necessary for efficient electrical power transmission over a long distance. However, electrical trees could grow in the cable systems, such as the cable insulation, joint and termination, eventually leading to insulation breakdown, therefore requiring serious attention. This paper concentrates on the effects of single-layer and double-layer barriers, which are improved techniques for suppressing electrical tree growth in silicone rubber with ethylene-vinyl acetate (EVA) as the barrier material. A simulation work using the finite element method was carried out on silicone composite with the barrier to study the influence of the barrier distance on the electrical tree propagation due to high electric field stress using a needle-plane electrode configuration. In addition, electric field distributions in silicone rubber with single-layer and double-layer barriers were investigated through experiment and simulation. The results illustrated that the electrical tree growth in the barrier region had been slowed down by the double-layer barrier, and the time to the breakdown had increased significantly.

Thermal aging management for electricity distribution networks: FEM-based qualification of underground power cables

It is well-known that there is no PLAN-DO-CHECK-ACT (PDCA) approach that is used by electricity distribution network operators and asset managers of power cable systems. Accordingly, this paper proposes a novel application of the PDCA approach to thermal aging management of underground power cables in electricity distribution networks. Another novelty of the proposed approach is that the finite element method (FEM) is used in combination with the traditional Arrhenius model to calculate the unknown temperature of cable conductors under service conditions. In particular, this means that the FEM-based Arrhenius model can involve the effects of other heat sources, wind, solar irradiation, etc., in procedures for qualification of underground power cables. The Arrhenius model is applied to an actual hot spot of a 110 kV underground cable line of most importance to reliable operation of the electricity distribution network of the city of Belgrade. In the hot spot, the 110 kV cable line is installed in parallel with the group of 35 kV cables and crosses an underground heating pipe-line. The proposed approach is successfully validated using the existing experimental data on cross-linked polyethylene insulation. Finally, it is found that the hot spot effect can shorten the expected total service lifespan of the 110 kV cables in the hot spot area by 36.84%, as well as that the largest consumption of total thermal lifespan occurs in the presence of all the existing thermal effects.

Harmonic-based 3D thermal analysis of thyristor-controlled reactor's power cable joints considering external electromagnetic fields

The power cable system of thyristor-controlled reactors (TCRs), particularly their terminations and joints, experience severe electro-thermal conditions because of current harmonics and external electromagnetic fields due to air-core reactors. Although several research works have been introduced for thermal analysis of power cable systems, there is a research gap in thermal analysis of special industrial cable systems, like the TCR's cables. This paper tries to fill such a research gap by proposing the harmonic-based 3D thermal analysis of TCR's cable joints considering the impacts of external electromagnetic fields. The superposition of thermal effects of current harmonics and external electromagnetic fields besides implementation defectiveness, such as imperfect connections, could make an extreme thermal condition, which is studied in this article. The evaluation of sheath bonding impacts on the thermal behavior of TCR's cable joint is another contribution. The proposed study is applied to an actual test system that previously experienced a fault in TCR cable joints by the COMSOL Multiphysics. The simulation results emphasize the effects of current harmonics on the thermal behaviors of the TCR's cable joints. Moreover, test results show that the implementation defectivenesses besides current harmonics and external electromagnetic fields could raise the joint temperature up to 100 °C.

Control of EMI in High-Technology Nano Fab by Exploitation Power Transmission Method with Ideal Permutation

There are many high-power electrical cables around and within semiconductor foundries. These cables are the source of extremely low-frequency (ELF < 300 Hz) magnetic fields that affect the tools which operate by the function of electronic beams. Miss operation (MO) happens because the ELF magnetic fields induce beam shift during the measurement or process for cutting-edge chips below 40 nm. We present the optimal permutation of power transmission lines to reduce electromagnetic influence in high-technology nano fabs. In this study, the magnetic field was reduced using a mirror array power cable system, and simulation results predicted the best permutations to decrease the electromagnetic interference (EMI) value to below 0.4 mG in a working space without any shielding. Furthermore, this innovative method will lower the cost of high-technology nano fabs, especially for the 28 nm process. The motivation behind this paper is to find the ideal permutation of power transmission lines with a three-phase, four-cable framework to decrease the EMI in high-technology nano fabs. In this study, the electromagnetic interference was diminished using the ideal-permutation methodology without investing or using additional energy, labor, or apparatus. Moreover, this advanced methodology will help increase the effectiveness and reduce the costs of nano fabs. The mathematical and experimental results of the study are presented with analysis.

Evolution of Temperature Field around Underground Power Cable for Static and Cyclic Heating

Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence.

Heat Dissipation in Variable Underground Power Cable Beddings: Experiences from a Real Scale Field Experiment

To prevent accelerated thermal aging or insulation faults in cable systems due to overheating, the current carrying capacity is usually limited by specific conductor temperatures. As the heat produced during the operation of underground cables has to be dissipated to the environment, the actual current carrying capacity of a power cable system is primarily dependent on the thermal properties of the surrounding porous bedding material and soil. To investigate the heat dissipation processes around buried power cables of real scale and with realistic electric loading, a field experiment consisting of a main field with various cable configurations, laid in four different bedding materials, and a side field with additional cable trenches for thermally enhanced bedding materials and protection pipe systems was planned and constructed. The experimental results present the strong influences of the different bedding materials on the maximum cable ampacity. Alongside the importance of the basic thermal properties, the influence of the bedding’s hydraulic properties, especially on the drying and rewetting effects, were observed. Furthermore, an increase in ampacity between 25% and 35% was determined for a cable system in a duct filled with an artificial grouting material compared to a common air-filled ducted system.

Technological Trend of Submarine Power Cable System for Floating Offshore Wind

Technological Trend of Submarine Power Cable System for Floating Offshore Wind

Investigation of Asymmetrical Three Phase Current and Impedance Variation in the Grid Connection of a HTS Power Cable

When a 22.9 kV, 50 MVA HTS (high temperature superconducting) power cable was applied to a real power system and the system was being operated as part of the Icheon project, a current redistribution problem occurred in the shield layer. To clarify the reasons for this, the authors analyzed the characteristics of the current distribution and induced current ratio with a phase angle in the HTS power cable considering an asymmetrical three-phase current that flowed into the conducting layer and the impedance variation of the shield layer according to a grounding method using the PSCAD/EMTDC (power system computer aided design/elector magnetic transients DC) analysis program and vector calculation. It was found that the increases in the asymmetrical current flowing through the conducting layer of the HTS power cable and in the impedance of the shield layer affected the magnitude and phase of the induced current. In addition, depending on the grounding method used, a problem in which the zero current generated by the asymmetry affects the induced current and flows through the cryostat was found. The results obtained through the simulation analysis will provide valuable information for the installation and operation of HTS power cable systems in actual utilities.

Optimization of Thermal Backfill Configurations for Desired High-Voltage Power Cables Ampacity

The ampacity of high-voltage power cables depends, among others, on their core cross-sectional area as well as thermal resistivity of the thermal backfill surrounding the cables. The cross-sectional area of the power cables’ core is selected according to the expected power to be transferred via the cable system. Usually, the higher the power transfer required, the higher the cross-sectional area of the core. However, the cost of high-voltage power cables is relatively high and strictly depends on the dimensions of the core. Therefore, from the economic point of view, it is interesting to focus on the improvement of the thermal condition around the cables, by changing the dimension of the thermal backfill, instead of increasing the power cables’ core cross-sectional area. In practice, it is important to find the optimal dimensions of both cable core and thermal backfill to achieve the economically attractive solution of the power cable transfer system. This paper presents a mathematical approach to the power-cable system design, which enables selecting the cost-optimal cross-section of a power cable core depending on the dimensions of the thermal backfill. The proposal herein allows us to indicate the condition in which it is advantageous to increase the core cross-sectional area or to expand the dimension of the backfill. In this approach, the optimal backfill geometry can also be evaluated. The investment costs of the 110 kV power cable system with the core cross-sectional areas consecutively equal to 630, 800 and 1000 mm2 have been compared.

A Novel Fault Location Method for Power Cables Based on an Unsupervised Learning Algorithm

In order to locate the short-circuit fault in power cable systems accurately and in a timely manner, a novel fault location method based on traveling waves is proposed, which has been improved by unsupervised learning algorithms. There are three main steps of the method: (1) build a matrix of the traveling waves associated with the sheath currents of the cables; (2) cluster the data in the matrix according to its density level and the stability, using Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN); (3) search for the characteristic cluster point(s) of the two branch clusters with the smallest density level to identify the arrival time of the traveling wave. The main improvement is that high-dimensional data can be directly used for the clustering, making the method more effective and accurate. A Power System Computer Aided Design (PSCAD) simulation has been carried out for typical power cable circuits. The results indicate that the hierarchical structure of the condensed cluster tree corresponds exactly to the location relationship between the fault point and the monitoring point. The proposed method can be used for the identification of the arrival time of the traveling wave.

Heat Storage of Paraffin-Based Composite Phase Change Materials and Their Temperature Regulation of Underground Power Cable Systems.

Excessive heat accumulation in backfill materials causes thermal fatigue damage in underground power cable systems that significantly affects the cable carrying capacity. To improve the thermal conditions of the system, two types of composite phase change materials (CPCMs) were prepared by incorporating paraffin into porous ceramsite (CS)/expanded graphite (EG) in this study. EG and CS can carry 90 and 40 wt.% paraffin, respectively. The phase change temperature of paraffin/CS and paraffin/EG CPCMs was approximately 65 °C, and the corresponding latent heats were 63.38 J/g and 156.4 J/g, respectively. Furthermore, the temperature regulation by CPCMs was evaluated experimentally by designing a setup to simulate the underground power cable system. The reduction in the maximum temperature of the backfill materials with paraffin/CS CPCM and paraffin/EG CPCM was approximately 7.1 °C and 17.1 °C, respectively, compared to reference samples. A similar conclusion was drawn from the heat flux curves. Therefore, the prepared CPCMs could significantly alleviate temperature fluctuations, where the paraffin/EG CPCM provided better temperature regulation than paraffin/CS CPCM. Both materials have potential applications for use in backfill materials for underground power cable systems.

Power cable vibration monitoring based on wireless distributed sensor network

Abstract Mechanical damage caused by construction, theft and transformation, has caused a long-term threat to the safe operation of cables. Owing to the complexity of cable distribution and operating environment, it seems impossible to apply traditional online monitoring systems with active alarms to power cable systems, especially considering the high cost of conversion and maintenance. In this paper, an integrated smart sensors based on MEMS accelerometers is proposed with the advantages of the self-organizing network, low latency, low power consumption according to the concept of Internet of Things, and a distributed cable monitoring method is described. Then, a diagnosis method based on the time-frequency characteristic parameters is exemplified.

Optimal Design of Functionally Graded Power Cable Joint Utilizing Silicone Rubber/Carbon Nanotube Composites

Functionally graded materials (FGMs) used in electrical insulation have spatially inhomogeneous dielectric properties (i.e., permittivity or conductivity), which can be applied to relieve localized electric field (E-field) intensification and improve insulation performance. However, previous research shows some limitations in inadequate considerations on the material feasibility, and insufficient universality on material grading type and voltage form. In this study, a material study of silicone rubber (SiR) nanocomposites containing carbon nanotubes (CNTs) is conducted to determine the practical variation range of dielectric properties (both permittivity and conductivity) in joint insulation materials. Then, the optimal design of both multilayer and pointwise FGM joint insulation is investigated under both AC and DC voltage, in which the lower and upper limits of permittivity and conductivity were derived from the experimental results. Experimental results on SiR/CNT nanocomposites indicate that low-amount doping of the CNTs (0-0.5% wt%) can effectively increase the permittivity and conductivity of joint insulation materials. The successive simulation study indicates that compared to uniform joints, cable joints employing optimally designed FGM insulation show a considerable increase in the E-field utilization factor (from 0.08-0.17 to 0.23-0.56), indicating elevated E-field uniformity. Finally, the optimal range of CNT doping ratios is determined to be 0-0.3 wt% from both experimental and simulation results. This study systematically verifies the applicability of FGMs in enhancing the performance of power cable accessories, which can show some guidance to the design and fabrication of advanced power cable systems.

Field Testing and Condition Assessment of MV Power Cable System by Very Low Frequency (VLF) AC Testing

Field Testing and Condition Assessment of MV Power Cable System by Very Low Frequency (VLF) AC Testing

Multiobjective optimization of underground power cable systems

This paper presents a modified Jaya algorithm (MJaya) for optimizing the material costs and electric-thermal performance of an Underground Power Cable System (UPCS). Three power cables arranged in flat formation are considered. Three XLPE high voltage cables are situated in the thermal backfill layer for ensuring the optimal thermal performance of the cable system. The cable backfill dimensions, cable backfill material, and cable conductor area are selected as design variables in the optimization problem. In the study, the Finite Element Method model is validated experimentally.The Particle Swarm Optimization (PSO), Jaya, and MJaya algorithms are used for multiobjective optimization in order to design a cable system in such a way to minimize the cable backfill costs and maximize the allowable electric current flowing through the cables. For the case study, calculations performed using the Jaya algorithm indicated 1.7 mln Euro cable system costs while cable ampacity is equal to I = 1460 A. The calculations are performed for the objective function values equal to w1 = 0.5 and w2 = 0.5. Such an optimization parameters set allow obtaining low costs of UPCS alongside with reasonable cable line ampacity.What is more, the results of the optimization obtained by Jaya, MJaya, and PSO algorithms are compared. Therefore, Coverage and Hypervolume metrics are incorporated. It is concluded that both the Jaya and MJaya algorithms performed better when compared to the PSO algorithm.

Development of a Wavelet – ANFIS Based Fault Location and Identification System for Underground Power Cables

Transmission lines are the backbone of electrical power systems and other power utilities as they are used for transmission and distribution of power. Power is distributed to the end-user through either overhead cables or underground cables. In the case of underground cables, their propensity to fail in service increases as they age with time. The increase in failure rates and system crashes on older underground power cables now negatively affect system reliability and involve numerous losses. It is therefore easy to realize that the consequences of this trend need to be managed [3]. Identification of the type of defects and their locations along the length of the cables is vital to minimize the operating costs by reducing lengthy and expensive patrols to locate the faults, and to speed up repairs and restoration of power in the lines. In this study, a method that combines wavelets and neuro-fuzzy techniques for fault location and identification are proposed. For this methodology a power transmission line model was developed and different fault locations were simulated in MATLAB/SIMULINK, and, as an input to the training and development of the Adaptive Network Fuzzy Inference System (ANFIS), certain selected features of the wavelet transformed signals were used. Fault index obtained from wavelet transformation are used as input variable for fuzzy input block function. Different membership functions were observed within input block function. As per formulation of rules, for membership function, the output value of the defuzzifier component was decoded to give a crisp value of ANFIS output. ANFIS results were compared with actual values. A comparison of the ANFIS output values and the actual values show that the percentage error was less than 1%. Thus, it can be concluded that the wavelet-ANFIS technique is accurate enough to be used in identifying and locating underground power line faults. Which will help in solving this time taking and tedious problem more efficiently and thereby reducing human effort in finding the type of fault and its location.