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This article introduces a novel Quantum-inspired Future Search Algorithm (QFSA), an innovative amalgamation of the classical Future Search Algorithm (FSA) and principles of quantum mechanics. The QFSA was formulated to enhance both exploration and exploitation capabilities, aiming to pinpoint the optimal solution more effectively. A rigorous evaluation was conducted using seven distinct benchmark functions, and the results were juxtaposed with five renowned algorithms from existing literature. Quantitatively, the QFSA outperformed its counterparts in a majority of the tested scenarios, indicating its superior efficiency and reliability. In the subsequent phase, the utility of QFSA was explored in the realm of fault detection in underground power cables. An Artificial Neural Network (ANN) was devised to identify and categorize faults in these cables. By integrating QFSA with ANN, a hybrid model, QFSA-ANN, was developed to optimize the network's structure. The dataset, curated from MATLAB simulations, comprised diverse fault types at varying distances. The ANN structure had two primary units: one for fault location and another for detection. These units were fed with nine input parameters, including phase-currents and voltages, current and voltage values from zero sequences, and voltage angles from negative sequences. The optimal architecture of the ANN was determined by varying the number of neurons in the first and second hidden layers and fine-tuning the learning rate. To assert the efficacy of the QFSA-ANN model, it was tested under multiple fault conditions. A comparative analysis with established methods in the literature further accentuated its robustness in terms of fault detection and location accuracy. this research not only augments the field of search algorithms with QFSA but also showcases its practical application in enhancing fault detection in power distribution systems. Quantitative metrics, detailed in the main article, solidify the claim of QFSA-ANN's superiority over conventional methods. [ABSTRACT FROM AUTHOR]

The traditional underground power cable fault positioning method relies on subjective parameter selection and noise resistance is poor. It cannot meet the accurate fault positioning requirements of underground power cable under strong noise background. In order to solve the above problems, a fault positioning method of underground power cable based on salp swarm algorithm (SSA) optimizing variational mode decomposition (VMD) combined with novel Teager energy operator (NTEO) is proposed. In response to the problem of modal aliasing, over decomposition, and under decomposition in signal decomposition of VMD, SSA is used to optimize the modal number K and penalty factor α of VMD parameters using fuzzy entropy as the fitness function. The intrinsic modal function that better reflects the fault feature information is obtained. NTEO is used to calibrate the first wave head to obtain the arrival time of the wave heads at both ends. The fault position is determined based on the dual end distance measurement method. PSCAD/EMTDC is used for underground power cable fault simulation. It simulates underground fault signals with strong background noise. The results show the following points. ① After adding 9 dB and 12 dB noise to the ideal current signal, the signal-to-noise ratio of SSA-VMD is the lowest, and the Pearson correlation coefficient is the highest. It indicates that SSA-VMD can effectively preserve the characteristic information of the signal while minimizing noise. ② Under different transition resistances, the positioning precision of SSA-VMD-NTEO is relatively high. ③ Under different fault phase angles, although SSA-VMD-NTEO may have different sampling points, the positioning position remains unchanged and still maintains high precision. ④ SSA−VMD-NTEO can ensure high positioning precision at different fault distances. ⑤ Under high underground noise and a sampling frequency of 10 MHz, SSA-VMD-NTEO has significant advantages in positioning precision compared to wavelet modulus maximum and VMD+NTEO methods.

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In underground cables of power systems, the maximum temperature of the cable is a crucial factor in determining its capacity. According to standards, the permissible operating temperature for the XLPE cable conductor under steady-state conditions is 90 °C – a limit that should not be exceeded. Exceeding this temperature may lead to a thermal breakdown in the cable insulation, thereby resulting in interruption of the electrical power supply. Many factors affect the cable temperature, particularly through the processes of heat dissipation and diffusion from the cable into its surroundings. These factors include soil types and compositions, cable installation configuration, and thermo physical properties; therefore, accurate analysis of these factors is crucial for cable loading. In this study, the finite element method (FEM) is employed to predict the cable temperature considering different soil compositions and to present a new approach for the thermal analysis of an underground cable system. The novel approach considers various environmental conditions including single-layer and multi-layer soil types, homogeneous and non-homogeneous soil compositions, two configuration types – flat and trefoil – as well as two types of backfill materials, specifically sand-cement mixture backfill (SCMB) and fluidized thermal backfill (FTB), and dry zones to offer deeper insight into a thermal analysis. Given that the FEM requires the construction of a complex geometric model within an optimal operating condition to obtain results with high accuracy—a process that can often be complex as well as not adaptable because it depends on constant mathematical calculation—This paper presents a novel approach FEM-BPNN that uses an adaptive Backpropagation neural networks (BPNN) model as its mainstay. The proposed BPNN model exploits historical data from FEM to refine its predictive power, therefore, increasing its efficiency and accuracy. Furthermore, the model is subject to an optimization process, adjusting and refining its internal parameters in response to new data, with the ultimate goal of improving the predictive model capabilities for the temperature of underground power cables. The results underscored the high performance of FEM in the simulation, and it was observed that FEM yielded results closely aligned with those of the IEC standard. Moreover, the proposed FEM-BPNN demonstrated exceptional accuracy, achieving a low RMSE score of 0.008. It also exhibited impressive performance in the linear regression analysis, with an R2 value of 0.99. These metrics collectively signify the robustness and efficacy of the model.

This work presents a multi-parameter optical fiber monitoring solution applied to an underground power distribution network. The monitoring system demonstrated herein uses Fiber Bragg Grating (FBG) sensors to measure multiple parameters, such as the distributed temperature of the power cable, external temperature and current of the transformers, liquid level, and intrusion in the underground manholes. To monitor partial discharges of cable connections, we used sensors that detect radio frequency signals. The system was characterized in the laboratory and tested in underground distribution networks. We present here the technical details of the laboratory characterization, system installation, and the results of 6 months of network monitoring. The data obtained for temperature sensors in the field tests show a thermal behavior depending on the day/night cycle and the season. The temperature levels measured on the conductors indicated that in high-temperature periods, the maximum current specified for the conductor must be reduced, according to the applied Brazilian standards. The other sensors detected other important events in the distribution network. All the sensors demonstrated their functionality and robustness in the distribution network, and the monitored data will allow the electric power system to have a safe operation, with optimized capacity and operating within tolerated electrical and thermal limits. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper aims to critically analyze the IEEE Std 1234-19 and other power cable fault-finding technical guides produced by leading industries to assess their applicability in practice to the underground low voltage distribution network (LVDN). The analysis reveals that there is no clear distinction between the fault-finding techniques and procedures of LV and MV/HV systems. Innumerable branching to residential loads in the underground LVDN makes them unsuitable to the application of most of the fault-finding techniques mentioned in the IEEE Std 1234-19 that are effective for MV/HV networks. Moreover, state-of-the-art techniques which are used as part of common industrial practice for LV fault-finding are not mentioned in the standard, nor collectively in any technical industry guide, which gives the impression that the content applicable to LV fault-finding is insufficient and lost amongst content only applicable to MV/HV fault-finding. In this paper, further contribution is provided; by means of presenting a recommended guide to fault-finding in the underground LVDN that will comprehensively fill in the knowledge gaps from the IEEE Std 1234-19 and other technical guides. The recommended guide presented in this paper is formed from practices reported in literature in addition to in-field case studies from one of UK’s largest energy providers; Scottish Power Energy Networks (SPEN) - part of Iberderola. The paper presents and discusses these literature-based and practical-based fault-finding practices, and uses them to construct the proposed guide which is presented in the form of a detailed flowchart procedure. This procedure is put forward to industry practitioners to be used in conjunction with existing technical standards and industry guides.

Magnetic fields and the shielding efficiency of the shields of underground high voltage cables are studied in this paper regarding several shielding configurations and materials. Shielding efficiency and magnetic fields are computed for shields with the same mesh but from different shielding materials, such as aluminum, ferrite, metal, and steel. In order to get the best shield configuration depending on the source characteristics and the material, a conducting ferromagnetic region with various thickness values is considered as shielding. A finite element model is introduced to investigate the influence of the parameters of magnetic fields and the shielding efficiency of underground high voltage cables. Furthermore, the reduction of the magnetic fields with or without shieldings is also presented. The developed method is performed with the magnetic vector potential formulations and validated on a practical problem. [ABSTRACT FROM AUTHOR]

The paper deals with the important challenges in terms of electricity transmission by means of underground cable lines. The power cable's performance is characterized by an ampacity that represents its maximum electric current-carrying capacity. The ampacity of power cables depends on their ability to diffuse the heat generated by the current flow into the environment. In the performed research, the analysis of the efficiency of heat dissipation from the cable is based on the measurement of temperatures at selected points in individual sections of the cable. As a consequence, the proposed test stand and applied research methodology are vital for the experimental evaluation of the analyzed thermal phenomena in the investigated underground cable lines. The research program covers an in-depth analysis based on the results related to the vital parameters of the investigated cable. The experimental methodology was used to analyze the influence of the properties of the medium surrounding the cable on its temperature, and thus on the ampacity of the cable. A novelty of this paper concerns the carrying out of the experimental laboratory research with actual measurements of the temperature distribution in specific points of the casing pipe based on the original test stand. The paper presents the novel concept of the developed stand for testing heat dissipation from the cable in a casing pipe with pipe sections filled with various media, equipped with a power supply system ensuring easy control of the power dissipated in the cable. The preliminary results of the comparative tests, in which the temperature distribution in the sections of the casing pipes was recorded, indicate that the findings are satisfactorily consistent with the assumptions related to the purpose of the research. The use of appropriate materials surrounding the cable contributes to more effective heat dissipation, and as it has been shown for the examined case in originally planned and conducted tests, it can lower the cable temperature by more than 20 °C, contributing to a significant increase in the ampacity of the cable. For example, it was recorded that for different media filling the pipes, the cable reached 30 °C with different currents flowing through cable of 60 A and 120 A, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dry zone formation around underground power cables during load cycling may lead to thermal failure of the cable's insulation. This phenomenon has to be recorded to send an alarm to the maintenance crew when the soil around the cable reaches the critical value at which the dry zone has started to be formed. In this study, the buried cable thermal model is modified to include occurrences of dry band formation during dynamic loading. An algorithm has been proposed for corrections of the cable load cycle to maintain the insulation maximum temperature at 85°C and not exceed this limit. This is suggested for reducing the dry zone formation effect on the cable insulation lifetime. The study is done on different single‐core cables using different soil samples that can be used as backfill materials. The variations in thermal soil resistivity and soil thermal capacitance with temperature and moisture content of backfill soil are considered. The practical system used for monitoring the dry zone formation around the cable has been proposed. [ABSTRACT FROM AUTHOR]

Formation of dry zones around power cables is an important factor affecting the cable loading and may lead to cable failure. This phenomenon is ignored by some standards in the calculation of power cables capacity. Numerous efforts have been done by many researchers for cable monitoring. In this study, monitoring system based on measurements of temperature distribution surrounding the cable route is suggested. When reaching the temperature of the dry zone formation the system will produce a warning alarm. To the best of the authors knowledge, the invention of a device that gives a warning in the case of drying layers formation around the power cables has not received attention so far. The proposed device is characterised by cheap price, high accuracy and its simplicity in the design. The system is tested in the laboratory using different soil types. Field tests are done to verify the reliability of the device. [ABSTRACT FROM AUTHOR]

This paper presents the laboratory test stand that is used for experimental validation of underground power cable system models. Determination of temperature distribution in the vicinity of the cable is the main goal of the study. The paper considers a system of three power cables, situated in the in-line arrangement, and buried in sand. Three electrical heaters of special construction are used in order to simulate the heat flux that is generated in the power cables during their operation. The test stand is designed to be placed in a thermoclimatic chamber, which allows testing the system in various thermal conditions when the ambient temperature changes by 20 °C to 30 °C. Numerical computations of the steady-state temperature fields are performed using the finite element method.

This paper deals with magnetic field mitigation techniques for underground power systems by using conductive or ferromagnetic shielding plates. Two new aspects are considered in this paper beside the shielding effectiveness analysis: the contribution to the series impedance and power losses due to the conducting set formed by the shielding plate/earth return path. A finite thickness ferromagnetic or conductive shielding is assumed buried parallel to the soil/air plane surface in order to model the induction magnetic field mitigation of a power underground cable system in flat configuration. An analytical method, appropriate to deal with possible optimization procedures, is used based on the magnetic vector potential for multilayered configurations where the shielding plate is treated as a different layer. Results for the magnetic field reduction factor at the soil surface are obtained for different shielding materials, different shielding thickness values, as well as different frequency values. Results are validated by employing the finite element analysis. [ABSTRACT FROM AUTHOR]

The paper presents an experimental investigation on the efficiency of different underground transmission/distribution line magnetic shielding techniques. Measurement results of magnetic field and temperature rise around the cable conductors are shown. An analysis of the thermal effects of each shielding technique on the line power capacity is presented. The experiments were performed on a test site where a real 138-kV underground cable section was built. The results provide useful information that can guide the designer when choosing the most suitable shielding technique according to the required shielding factor taking into account its impact on the line-rated power. [ABSTRACT FROM AUTHOR]

There are important concerns about the problems caused by high values of low-frequency magnetic field in urban centers. Two of them have received particular attention: the electromagnetic interference in sensitive equipment and the potential adverse health effects on human beings. In this way, many solutions to mitigate the magnetic field generated by these lines have been proposed. In this context, this work presents several computational results about the effectiveness of the main forms to reduce the magnetic field generated by underground power cables. The analysis addresses not only the field attenuation levels, but also the impact on the rated current due to the presence of shielding devices. From these results, it is possible to choose the best shielding arrangement for each specific situation, in order to achieve the required attenuation levels with the least ampacity loss. The thermal-magnetic model was implemented in the (free) software FEMM 4.2, which employs the finite element method. [ABSTRACT FROM AUTHOR]

Traditionally, extra high voltage (EHV) transmission systems consist exclusively of overhead lines (OHL) but in the recent years the utilization of high voltage AC (HVAC) power cables is increasing due to environmental, political and operational aspects. To study the impact of HVAC power cables on temporary overvoltages and slow front transients, a simulation model of the large-scale network is required. Guidelines concerning the modeling detail for the surrounding network need to be established to ensure sufficient accurate results. Existing guidelines for purely OHL transmission networks may not be adequate since the integration of HVAC power cables shift the harmonic impedance of the network to lower frequencies and that can affect the extent of the needed simulation model. Much effort can be saved from obtaining detailed data for an extensive but proper model, but a less detailed model might not describe the network behavior with sufficient accuracy. In this study, simplification options are considered, for which the time to construct and analyze a simulation model can be reduced. The simplification options are compared with the reference model (full detail), and judged based on three indicators for the level of accuracy: frequency and amplitude of the main resonance, and maximum over-voltage. As a result, guidelines on the extent of the simulated network and in which detail the model has to be built are proposed. The inverse approach, i.e. increasing level of detail until simulation results hardly change leads to similar results, but requires equivalent short-circuit networks for the rest of the grid. The method is tested for the Dutch 380 kV grid where an underground cable connection of 10.8 km length is introduced in 2013 and a second connection is planned for 2017. [ABSTRACT FROM AUTHOR]

Developments in the electricity sector, related to integration of sustainable energy, not only affects the medium voltage but also the low voltage infrastructure. Condition monitoring of Low Voltage (LV) underground power cables becomes of increasing interest to safeguard reliable power delivery. Since the start of phasing out oil-paper insulated cables, polymeric insulation is most widely applied. As phenomena associated with high electric field stresses are not expected, little is known about the degradation mechanism of LV cables with polymeric insulation. External damage is known to be a major cause of defects, which directly causes a failure or initiates degradation resulting in a failure later on. To study the degradation mechanisms, short cable sections with artificial damage have been subjected to periodic water exposure in the laboratory. This shows that dry-band arcing is a major mode of degradation, with accumulation of pollutants due to chemical decomposition. Several factors such as water conductivity, presence of oxygen, soil type and insulation material have been investigated. Strong dependencies upon these parameters are observed. However, it may be hard to quantify the degradation process in practical situations. The presence of a water film that can sustain dry-band arcing will occur only in certain situations and for limited amount of time. However, the accumulation of these events, mainly caused by periods of precipitation, will eventually lead to breakdown at the damaged spot. [ABSTRACT FROM PUBLISHER]

Current monitoring can facilitate preemptive action in electrical distribution network, so as to relieve power congestion, improve transmission efficiency, and ensure network reliability. The non-invasive current sensing devices are promising since they do not require contacting hazardous high voltage and their installation is much easier compared with invasive current sensing devices. However, the existing non-invasive current sensing devices, such as current clamps and Rogowski coils are only applicable for measuring single-core underground power cables. In this paper, we established a non-invasive technique, that can monitor the currents of a multi-core underground power cable by measuring the emitted magnetic field around the cable surface. The additional magnetic fields generated by induced and leakage currents on the cables were firstly evaluated. Magnetoresistive (MR) sensors in a circular array were adopted to measure magnetic field around the cable surface, and a triple-layer shielding was designed to reduce the effects of external interference. Regarding intrinsic noise in MR sensors (e.g., 1/f noise and thermal noise), magnetic flux concentrators were supplemented to improve the signal-to-noise ratio. The developed platform was tested in a substation, and the reconstructed results closely matched the real geometrical configuration and current records of the tested cable. Apart from the non-invasive feature, the platform also shows great potential to improve the sensing capability of current amplitude and frequency compared with CTs by adopting MR sensors. [ABSTRACT FROM PUBLISHER]

This study presents a fault‐location technique for multi‐terminal multi‐section non‐homogeneous transmission lines which combine overhead lines with underground power cables, by using voltage and current synchrophasors obtained from phasor measurement units. First, a faulty line branch is selected to narrow down the suspected faulty area. Then, the faulty section and the exact fault location can be identified by calculating the normalised fault distance for each section on the selected faulty branch. Computational burden of the proposed analytical scheme is very low because it avoids iterative computations. Promising simulation results show that the proposed fault location technique can accurately locate the fault regardless of the fault type, fault resistance, fault location, pre‐fault loading and line parameters inaccuracies. [ABSTRACT FROM AUTHOR]

A graphical method based on error images to validate the accuracy of two of the most important recently published ground-return impedance models of underground power cables is described in this letter. [ABSTRACT FROM AUTHOR]

This paper presents the preliminary thermal analysis of the underground transmission line, which will be applied in the Polish power plant that produces 600 MW of power. The paper considers a system of three power cables located in the in-line arrangement placed in the HDPE casing pipes buried in the multilayered soil (the native soil and the thermal backfill). Different configurations of bedding layers are analyzed. The burial depth of the cables, measured from the reference level (0.5 m below the ground) varies from 2 to 6 m. What influences the temperature distribution in soil, cable bedding and cable conductor. The numerical computations of the steady-state temperature fields are performed using the finite element method. Additionally, to include the dry-zone formation effect on the temperature distribution, the soil thermal conductivity is considered to be temperature-dependent. [ABSTRACT FROM AUTHOR]

This paper presents the thermal analysis of the underground transmission line, planned to be installed in one of the Polish power plants. The computations are performed by using the Finite Element Method (FEM) code, developed by the authors. The paper considers a system of three power cables arranged in flat (in-line) formation. The cable line is buried in the multilayered soil. The soil layers characteristic and thermal properties are determined from geological measurements. Different conditions of cable bedding are analyzed including power cables placement in the FTB or direct burial in a mother ground. The cable line burial depth, measured from the ground level, varies from 1 m to 2.5 m. Additionally, to include the effect of dry zones formation on the temperature distribution in cable line and surroundings, soil and FTB thermal conductivities are considered as a temperature-dependent. The proposed approach for determining the temperature-dependent thermal conductivity of soil layers is discussed in detail. The FEM simulation results are also compared with the results of the simulation that consider soil layers as homogeneous materials. Therefore, thermal conductivity is assumed to be constant for each layer. The results obtained by using the FEM code, developed by the authors, are compared with the results of ANSYS simulations, and a good agreement was found. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to quantify the effect of customer-owned distributed generation (DG) units on the life expectancy of power cables. Numerical results obtained from a realistic distribution system are presented and discussed under various scenarios, including different penetration levels of DG technologies. The results show that despite differences among various DG technologies, significant benefits can be realized in the area of power cable life extension, when DG units are installed by low-voltage customers. However, the extent of the benefits largely depends on the penetration level of DG units, the production pattern of DG technologies and the utilization factor of the analyzed cables. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We are all used to the possibilities made available by the Internet and information and communications technology (ICT), but only those of us who are at least in our 40s can truly appreciate the difference between the present day and the time when rapid long-distance bidirectional communication could only take place via telegraph, telephone, and telex. A similar revolution occurred in the late 1830s with the invention of the telegraph, the first electric technology to gain wide success. However, this pioneering equipment performed badly; with the conductivity of commercial copper around 40% lower than its present value and insulating material unreliable, it was a common practice to lay bare overhead lines hanging on wooden poles with glass or porcelain insulators. [ABSTRACT FROM PUBLISHER]

This paper presents a novel technique to evaluate the electric power losses in MVAC and HVAC three-core XLPE cables. The proposed formulation allows to evaluate these losses without power flow simulations by shaping it either in a spreadsheet or in algorithmic form. The formulation can be easily set out within wider methods such as those used to evaluate the energy yield of offshore wind power plants (OWPPs) in cost-benefit analyses, or those used to evaluate techno-economically the alternatives in power system new asset optioneering. The avoidance of power flow simulation requirements contributes to a significant decrease in the time needed to conduct the studies and to an increase in the number of engineers and researchers able to fulfil them. Finally, the proposed formulation has been checked thoroughly and the validation is carefully addressed in the text. [ABSTRACT FROM PUBLISHER]

In electromagnetic transient analysis, one major issue is the influence of the imperfect earth on the propagation characteristics of transmission line conductors. Extensive research has been published for overhead lines, whereas the corresponding literature for underground cables is significantly less. Recently, new expressions for the calculation of the ground impedance and admittance have been proposed for the homogeneous and the stratified earth case. However, most transient simulation programs still use approximate earth representations. Scope of this study is to compare the proposed formulation with the corresponding approximations, in order to introduce a frequency limit for the use of the approximate earth models, sas well as criteria that dictate the use of a stratified earth model. The resulting propagation characteristics are used in transient calculations, in order to validate the effect of the differences by the various approaches and the need to include a more accurate model in the simulation of underground cable transients. [ABSTRACT FROM AUTHOR]

This paper presents an application of a cable fault localization using an instantaneous frequency (IF) estimation in the Gaussian-enveloped linear chirp (GELC) reflectometry. The GELC reflectometry sends a GELC signal into a cable and measures the reflected signals from the faults. A fault distance is calculated by the estimated time delay between the incident and reflected signals. The cross-correlation method for estimating time delay can be affected by the propagation characteristics of the cable and this results in the time offset in the time delay estimation. To reduce the time offset, we propose an IF-estimation-based fault-localization method. The proposed method uses the statistical-model-based detection with the hidden Markov model and the constrained Kalman filtering for estimating the IF of the GELC. We can obtain the time delay between the incident and reflected signals by calculating the time delay between the center frequencies corresponding to the incident and reflected signals, respectively. Experimental results show that the proposed method estimates the accurate fault distance without the compensation term for the time offset. Therefore, the proposed method is an appropriate method for estimating the fault localization in a cable. [ABSTRACT FROM PUBLISHER]

The fault location in underground cables is characterized as the technical difficulties due to complexities in cables. Based on the direct circuit analysis, a fault location algorithm for underground cables with no laterals is presented in this paper. The single-end phasor measurements, including the voltages and currents sampled in the substation side, are utilized to locate the single phase faults in the typical single-conductor cross-linked polyethylene (XLPE) cables rated at the medium voltage (MV) levels. The distinctive cable characteristics are considered, such as relatively large capacitance, effects of sheaths and sheath bonding methods. The different fault scenarios are taken into account as well. The effect of changes of cable parameters and application of static response load model are also investigated. The simulation studies demonstrate the proposed algorithm can achieve the high accuracy under various system and fault conditions. [ABSTRACT FROM AUTHOR]

This paper analyzes the thermal effects derived from the use of different screen shapes when shielding the magnetic field generated by underground power cables. A parametric analysis is developed to show the influence of the geometrical and the electrical parameters of the shield on the maximum temperature achieved by the power cables in order to analyze the impact of this technique on the ampacity of the line. A 2-D finite element approach is employed in this study to verify the performance of different types of screens (horizontal plate, reverse-U, and H-layout) in terms of shielding efficiency, overheating of the power cables, and operational costs. [ABSTRACT FROM AUTHOR]

The present study, the second of three parts, deals with pilot projects performed on the rejuvenation of 28-kV extruded cables. Thirteen triplexed XLPE cable sections, with 500- or 750-kcmil compact conductors, on two distinct lines 1 and 1.2 km in length installed in a duct system, have been injected with silicone by a service provider. The main objective of this second part is to validate the applicability of the silicone injection technique, focusing primarily on the method to implement the technique. It was found that the silicone injection technique can be successfully used in a conduit system applying the injection by cable section, although silicone leaking occurred at some cable ends. Furthermore, the double injection method was found to be less time consuming compared to an injection done by cable section, and particularly to an injection done by line. [ABSTRACT FROM AUTHOR]

Many factors affect the loading of the underground power cables, such as ambient temperature, depth of laying of cable, number of parallel circuits of cable, and thermal resistivity of the surrounding soil. One important factor, usually ignored, is the formation of dry zones around the underground power cables. Dry zones are usually formed around underground power cables under loading conditions due to the migration of moisture within the soil. In this paper, the effect of the formation of the dry zone on the ampacity of underground power cables is investigated. The derating factor for the formation of dry zones around underground power cables is suggested and calculated for different types of natural backfill soil. IEC 60287-1-3 is taken as a reference. Experimental work was conducted to study the phenomena of the dry zone as related to different types of soils. [ABSTRACT FROM AUTHOR]

This paper analyzes the possibility of using compensated passive loops to obtain a high mitigation effectiveness of the magnetic field generated by underground single-core cables. With that aim, several loops arrangements are simulated in a case study, including new ones called enchained loops, whose geometry reminds short-circuited conductors at both ends, but with the advantage of requiring smaller compensating capacitors. The results show a drastic spot reduction in several configurations, but with the drawback of high sensitivity to parameters. This aspect should be taken into account in the final design, so a design procedure is proposed that includes measures to alleviate this problem. Eventually, a comparison using shielding with high-conductivity material is provided. [ABSTRACT FROM AUTHOR]

The transmission characteristics of underground medium-voltage/broadband over power line (MV/BPL) channels are examined analytically. By appropriately modifying multiconductor transmission-line theory, the bottom-up approach, already used to treat overhead MV/BPL transmission, is extended to analyze BPL transmission in three-phase underground MV lines with common shield and armor. ThIS analysis shows that these cables may support five modes, giving rise to five separate transmission channels which reduce to three if the shield and armor are grounded. The numerical results concerning attenuation in underground MV/BPL channels have been validated against relevant sets of measurements and compared to the relevant results of overhead MV/BPL channels. It has been verified that the attenuation in underground MV/BPL channels exhibits a lowpass behavior and is significantly higher than that of overhead ones. [ABSTRACT FROM PUBLISHER]

This paper presents a method for configuring the locations of any number of cables, for the best total ampacity. The optimal configuration is determined through a proposed two-level optimization algorithm. At the outer level, a combinatorial optimization based on a genetic algorithm explores the different possible configurations. The performance of every configuration is evaluated according to its total ampacity, which is calculated by using a convex optimization algorithm. The convex optimization algorithm, which forms the inner level of the overall optimization procedure, is based on the barrier method. The proposed approach is tested for a duct bank installation containing 12 cables and 15 ducts, comprising two circuits and two cables per phase, and compared with a brute force method of considering all possible configurations. The proposed approach is also applied to an installation consisting of a single circuit inside a large magnetic steel casing. [ABSTRACT FROM PUBLISHER]

This work present a modeling of underground isolated power cables through the coupled magnetic-Eddy current and thermal formulations solved using the finite element method (FEM). The governing magnetic and electric fields equations expressed in term of Magnetic- Vector-Potential (MVP) is strongly coupled with total Current density equation which include Eddy current (EC), source and Displacement Current densities which permit to take into account the skin and proximity effects. The computed (EC) density losses are introduced as heat source in the free transient thermal equation associated with the convection heat transfer. The thermal analysis solved using the iterative time-stepping algorithm and (FEM) lead to the temperature distribution at each step time. A single and multicircuit three-phase underground power cables arrangements are presented as the analysis devices in order to analyse the magnetic flux density and the time-space temperature. [ABSTRACT FROM AUTHOR]

Abstract: In a power transmission cable system, the uniformly configuration of the cables between sections is sometimes difficult to achieve because of the geometrical limitation. This will cause the increase of sheath circulating current which results in the increase of sheath loss and the decrease of permissible current of the power transmission system. While the cable is on operation, because of cable aging and other unexpected reasons, sheath fault always occurs which leads to the further damage of the insulation layer and the life of the cable. These two problems were particularly addressed in this paper. Over last few years, two research groups in South Korea and the United Kingston have worked together extensively to solve these problems and made some great achievements. For tackling the problem of the increase of sheath circulating current, one special device was designed to measure this kind of current; an effective measure was proposed to reduce the current and the new measure was well protected from any further threats like cable fault and lightning. Regarding the problem with sheath fault, one data acquisition system was designed to monitor the sheath fault on field; a new fault phenomenon was discovered for the cable buried in sand; based on the new discovery, the fault was characterised, modelled and simulated; furthermore advanced signal processing techniques were introduced to extract the fault signals from the sheath, detect and locate the fault. These new solutions have either been successfully applied in practical operation of the power cable system or used in further research to propose more advanced solutions. The paper reviewed the latest developments of these new solutions. [Copyright &y& Elsevier]

Endurance of an insulation material to high temperatures determines the maximum current-carrying capacity (ampacity) of an underground power cable. Cable ampacity is calculated conventionally using the installation conditions and maximum steady-state operation temperature according to IEC-60287 standard. In this article, finite element method results are compared with IEC-60287. A further verification has also been made with experiments. In this work, ampacity analyzes of 154 kV high voltage XLPE underground power cable are made using ANSYS 5.61 finite element analysis software. An experimental set-up is developed to measure conductor and surface temperature of the cable in underground conditions. The results of experiments and numerical calculations are compared to the IEC-60287 standard. Additionally, the thermal regions of three cables in flat installation are investigated to show the versatility of the finite element method. The effects of insulation thickness and external thermal source on ampacity are also analyzed using the finite element method. [ABSTRACT FROM AUTHOR]

This paper presents a variety of viewpoints from engineers within the power cable industry as to how current trends in the cable industry will influence future cable designs, particularly with polymeric insulation, lapped dielectrics, and improved diagnostic techniques. The use of high-temperature superconductors and designer polymers as well as the possible availability of conducting polymeric materials is also considered. The paper first reviews how the design of distribution cables has differed historically around the world, the major differences being allied to the systems. Designs largely have been divided into two main categories: those countries following U.K. and European practices, and those having adopted the U.S. system design. However, these differences, such as the use of three-phase cables in the U.K. as opposed to single-phase cables in the U.S., are not so obvious nowadays. Installation practices are becoming rather more standardized, such as the use of ducts, directional drilling, etc. The predominant primary insulation is cross-linked polyethylene (including tree-retardant XLPE), which is used all around the world. Some constructional differences such as the "dry" and "wet" designs persist. The paper then discusses cables from the mid-twentieth century projected into the twenty-first century. Highlighted are the opportunities that will present themselves in the twenty-first century: fluid-filled cables, XLPE cables, intelligent cables, and designer polymers that optimize performance and economic advantages of buried cables. It then focuses on economic trends, power generation trends, lower-cost underground systems, overhead line/underground cables, and materials and environmental trends including use of high-temperature conductors to up-rate overhead circuits. The trend will be toward greater security and utilization using on-line diagnostics, greater circuit diversity due to distributed generation and lower cost cable systems, and extensive use of polymeric materials having low environmental impact. A futuristic view of energy cables in the year 2050 is presented. Discussed are the elements of the "info-energy cable," the advantages of the cable technology, and the advantages for the network configuration. A realistic view of tendencies in cable systems technology over the next decade is outlined. Also discussed is choice of cable for subsea power links: choice of cable design that exists for subsea power links, the merits of the various designs, installation of submarine cables, protection of submarine cables, new challenges in HVdc submarine cable systems, and future developments. The manufacture and installation of long continuous lengths of subsea power cable is discussed with reference to some key installations. The paper goes on to examine the Kontex HVdc link between Denmark and Germany. The cable link has been in commercial operation since 1996, and with a total length of 172 km and a transmission capacity of 600 MW at 400 kV is still unique worldwide. Details of the link together with its installation and commissioning are explained. Gas-insulated transmission lines are also discussed together with whether they are ready for real-world transmission systems. [ABSTRACT FROM AUTHOR]

• Signal propagation modes along power cables with asymmetric structure are studied. • Validity of the modes is verified by Rayleigh-Schrödinger perturbation analysis. • Asymmetries caused by geometric design and temperature distribution are analysed. • Asymmetry affects propagation modes mainly via the dielectric material properties. Locating defects in an underground cable connection can be based on the propagation of transient signals emerging from faults or weaknesses in the insulation. The accuracy depends on the precise knowledge of the propagation characteristics of high-frequency components in the signals. These characteristics are analysed for multi-conductor cables in case of non-perfect rotational symmetry. Deviations can arise from the positioning of the conductors within the cable cross section or from an inhomogeneous distribution of dielectric materials. It is investigated to what extent the signal propagation modes, applicable for a symmetric configuration, remain a suitable representation for signal interpretation when the symmetry is slightly disturbed. This is judged by means of Raleigh-Schrödinger perturbation analysis in comparison to electromagnetic field simulations. Cable designs for the medium-voltage level incorporate measures to confine the electric field in designated regions. Slight asymmetry does not lead to strongly perturbed modes. For low-voltage cables, electric field control is not needed, and the conductors are positioned within short distance of each other. Modes can change significantly upon a relatively small asymmetry. Inhomogeneous heat dissipation, e.g. from a short-circuit current upon a fault, can cause a temporarily asymmetric permittivity distribution over the cable cross section. The feasibility to detect such effect from changing signal velocities of the propagation modes is discussed. [ABSTRACT FROM AUTHOR]

This paper presents the laboratory test stand that is used for experimental validation of underground power cable system models. Determination of temperature distribution in the vicinity of the cable is the main goal of the study. The paper considers a system of three power cables, situated in the in-line arrangement, and buried in sand. Three electrical heaters of special construction are used in order to simulate the heat flux that is generated in the power cables during their operation. The test stand is designed to be placed in a thermoclimatic chamber, which allows testing the system in various thermal conditions when the ambient temperature changes by 20 °C to 30 °C. Numerical computations of the steady-state temperature fields are performed using the finite element method. [ABSTRACT FROM AUTHOR]