Power Transmission Cables Research Articles

Optimal Design of High-Power Density Medium-Voltage Direct Current Bipolar Power Cables for Lunar Power Transmission

Power systems on the lunar surface require power lines of varying lengths and capacities to connect generation, storage, and load facilities. These lines must be designed to perform efficiently in the harsh lunar environment, considering factors such as weight, volume, safety, cost-effectiveness, and reliability. Traditional power transmission methods face challenges in this environment due to temperature fluctuations, micrometeoroid impacts, and ionizing radiation. Underground deployment, although generally safer, faces challenges due to low soil thermal conductivity. At a depth of 30 cm, the lunar temperature of −23.15 °C can be advantageous for managing waste heat. This study presents a novel approach, developed using COMSOL Multiphysics, for designing bipolar MVDC cables for lunar subsurface power transmission. Kapton® MT+ is chosen as the insulating material for its exceptional properties, including high thermal conductivity and superior dielectric strength. The cables are designed for voltages of ±10 kV and ±5 kV and capacities of 200 kW (low power), 1 MW (medium power), and 2 MW (high power). Our findings indicate that aluminum conductors offer superior performance compared to copper at medium and high power levels. Additionally, elevated voltage levels (±10 kV) enhance cable design and power transfer efficiency. These specially designed cables are well-suited for efficient operation in the challenging lunar environment.

The role of inter-island transmission in full decarbonisation scenarios for Indonesia’s power sector

Indonesia has large renewable energy resources that are not always located in regions where they are needed. Sub-sea power transmission cables, or island links, could connect Indonesia’s high-demand islands, like Java, to large-resource islands. However, the role of island links in Indonesia’s energy transition has been explored in a limited fashion. Considering Indonesia’s current fossil fuel dependency, this is a critical knowledge gap. Here we assess the role of island links in Indonesia’s full power sector decarbonisation via energy system optimisation modelling and an extensive scenario and sensitivity analysis. We find that island links could be crucial by providing access to the most cost-effective resources across the country, like onshore photovoltaics (PV) and hydropower from Kalimantan and geothermal from Sumatera. In 2050, 43 GW of inter-island transmission lines enable 410 GWp of PV providing half of total generation, coupled with 100 GW of storage, at levelised system costs of 60 US$(2021)/MWh. Without island links, Java could still be supplied locally, but at 15% higher costs due to larger offshore floating PV and storage capacity requirements. Regardless of the degree of interconnection, biomass, large hydro, and geothermal remain important dispatchable generators with at least 62 GW and 23% of total generation throughout all tested scenarios. Full decarbonisation by 2040 mitigates an additional 464 MtCO2e compared to decarbonisation by 2050, but poses more challenges for renewables upscaling and fossil capacity retirement.

A Literature Survey on Underground Cable Fault Detection using IoT

The rise in use of Underground Cables for power Transmission is recent times due to its less maintenance and lower susceptibility to damage by weather, means that detection of any other faults that occur in them must be swift and efficient to ensure lower down-Time in transmission and supply. The survey goes through various fault detection methods that have been proposed, to find potential pros and cons and attempts at bettering them. While using various AI models in detection can be highly accurate to the cause, it still has some error margins to it. On the other hand using IoT (Microcomputers and sensors) make up for near perfect detection increasing the efficiency of the system. This requires a wide range of understanding on the topics of electricity and the working of these lines which is the goal of this paper

Research and Analysis of the Cost of Right of Way for Conventional Overhead Transmission Lines and Power Transmission Cable

The study explores the pros and cons of adding these advanced conductors to transmission lines. This study examines the costs of procuring RoW for standard overhead transmission lines and power transmission cables. The report details the costs and considerations of obtaining land for power transmission infrastructure. Research has two main parts. The document begins with transmission asset owner’s RoW acquisition methods and rules. It explains the regulatory framework and mechanisms for securing land rights for power transmission infrastructure. The second section analyses costs in detail. It compares the economics of installing overhead transmission lines with power transmission cables, focusing on subsurface XLPE cables. The study examines how RoW acquisition affects adjacent land prices and the economic effects on TAOs and surrounding communities. The research also evaluates transmission line dismantling costs, including waste metal value, considering metal price changes. RoW costs persist after the transmission line's tenure. The paper also examines a replacement model that estimates RoW costs for switching from overhead transmission lines to underground XLPE cables for outmoded transmission infrastructure. This analysis seeks to illuminate RoW Acquisition's financial elements for power transmission decision-makers.

Development of Simulation Model of Single-Phase Circuit Lock in the Digsilent Powerfactory Program

Abstract The most common types of damage in distribution networks with a voltage of 6-35 kV have been analyzed. It is shown that the majority of them are single-phase circuits, which can cause overvoltages at the point of damage and negatively affect electrical equipment, which can lead to a decrease in economic indicators. The methods of increasing the reliability of distribution networks with a voltage of 6-35 kV have been analyzed. The main attention is focused on the method of increasing reliability due to grounding of the neutral through an arc reactor, the main advantage of which in operation is the continuation of single-phase ground fault operation without disconnection of consumers. A simulation model of the distribution network in single-phase ground fault mode was developed and its main parameters were calculated. The DiGSILENT PowerFactory software complex is used as a simulation environment. A concrete example of parameter calculation when using the proposed simulation model in the DiGSILENT PowerFactory program, which contains 5 overhead and 5 cable power transmission lines with a voltage of 35 kV with a length of 10 to 100 kilometers. The use of this model will make it possible to study transient processes in the mode of single-phase grounding, to prevent emergency situations in distribution networks. The goal of the work ist development of the simulation model of the distribution network in the mode of single-phase circuit to land and the calculation of its basic parameters.

Red rock crab (Cancer productus) movement is not influenced by electromagnetic fields produced by a submarine power transmission cable

Marine renewable energy (MRE) devices, such as ones that harness offshore wind and wave energy, are an effective supplement to traditional energy sources and can support the energy grid while combating climate change. As MRE development increases pace, it is important to anticipate impacts of these infrastructure projects on the marine environment. One potential impact is a localized change in electromagnetic fields (EMF) produced by energized submarine transmission cables. Though many marine species are sensitive to EMF, primarily for navigation and orientation purposes, strong conclusions about how EMF affects invertebrates are lacking. Organisms that traverse the seafloor close to energized submarine cables, such as crabs, may be subject to stronger EMF currents. The U.S. West Coast is both a hot spot for emerging MRE development as well as home to the largest crab fisheries in the nation, there is an obvious concern on the potential impact development will have on fisheries. Our primary objective was to verify the response of red rock crabs in the presence of energized cables similar to those associated with existing MRE installations while also controlling for environmental conditions. We quantified and mapped local magnetic fields near an energized cable, tested crab responses in cable and control areas using a two-choice experimental cage in situ and described and quantified variables that were most likely to affect crab responses, including water current direction/velocity and magnetic field strength. Our results were remarkably consistent with previous studies: 1) crabs showed no preference for crossing/not crossing the cable; 2) crabs preferred to travel to the west regardless of the presence/absence of an energized cable; 3) while crabs preferred to travel to the west even more frequently in the absence of an energized cable, cable crossing and travel direction preferences were not influenced by EMF; and 4) EMF produced by these cables were consistent over time and decay to background levels at a distance of less than 1 m. This information is critical to making informed and sustainable policy decisions about renewable energy development and ensuring that this technology can coexist with local fisheries as MRE development continues.

Chemical Property Evaluation and Tensile Strength Correlation of XLPE Insulators Based on Accelerated Thermal Aging

Cross-linked polyethylene (XLPE) cable is a representative power transmission cable. XLPE has excellent mechanical properties, chemical and heat resistance, and insulation. However, XLPE insulation deteriorates during operation due to electrical, mechanical, and thermal stresses. Among these, thermal stress is a major factor and reduces insulation properties due to a change in molecular structure. Therefore, XLPE characteristic evaluation by heat exposure is essential for power cable condition evaluation. Herein, deteriorated XLPE samples were characterized by tensile strength, X-ray diffraction, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and ultraviolet-visible spectroscopy after exposure to various temperatures and durations. Comparing the tensile strength with other analysis results yielded correlations. Each characteristic showed a linear relationship. The correlation between tensile strength and carbonyl index was the strongest, and the coefficient of determination, R2, was 0.9299. Therefore, these results will provide important information on chemical properties when establishing operational management standards for XLPE insulators in the future.

Features, events and processes (FEP) analysis of the interactions between repository monitoring systems and multi-barrier systems

Abstract. In line with the European waste directive 2011/70/EURATOM, the European Joint Programme on Radioactive Waste Management (EURAD) was launched in June 2019. EURAD aims to make a step change in European collaboration between advanced and early-stage waste management programmes. Monitoring Equipment and Data Treatment for Safe Repository Operation and Staged Closure (MODATS) is Work Package (WP) 17 of the EURAD programme. This WP aims to address a range of research needs relating to repository monitoring data and technologies. This abstract summarises research relating to the interactions between repository monitoring systems and the multi-barrier systems in which they are emplaced. A detailed features, events and processes (FEP) analysis is being undertaken to identify and describe the manner in which monitoring systems may interact with multi-barrier systems. Monitoring system components are generically considered in this research; they include data acquisition technologies, power technologies, data transmission technologies and data loggers. No specific disposal concepts have been selected; however, a range of commonly engineered barrier system materials and typical host rocks are considered. This FEP analysis research will provide an understanding of the impacts of monitoring systems, which could be used to aid monitoring system design optimisation, for example by supporting the screening of monitoring technologies (White and Scourfield, 2019). It may also provide evidence to demonstrate that monitoring systems do not unacceptably impact the safety functions of the multi-barrier system. Potential interactions may include the creation of gas migration pathways along monitoring power or data transmission cables positioned in the multi-barrier system. This process has been observed in underground research laboratory experiments, such as the Large Scale Gas Injection Test (LASGIT) experiment in the Äspö Hard Rock Laboratory, which involved a series of gas injection tests in a full-scale KBS-3V deposition hole. Other possible interactions could include (non-exhaustive) corrosion of metallic components, degradation of non-metallic components, microbial activity, gas generation, void introduction and formation and volume changes. The final output of this research will be a catalogue of FEPs describing the interactions between generic monitoring systems and multi-barrier systems. Similar to the Nuclear Energy Agency FEP lists, this FEP catalogue is intended to be a starting reference for waste management organisations to use to understand the potential interactions between their specific monitoring systems and multi-barrier systems.

Ice Adhesion Evaluation of PTFE Solid Lubricant Film Applied on TiO2 Coatings

Ice formation affects the performance of many industrial components, including aircraft wings, spacecraft, and power transmission cables. In particular, ice build-up on airplane components increases drag and fuel consumption. A large number of studies have been carried out to reduce ice adhesion by developing passive methods such as icephobic coatings and active ice removal approaches such as mechanical vibrations or chemical-based solutions. Despite remarkable recent breakthroughs in the fabrication of icephobic coatings, passive ice removal solutions require higher durability to resist cyclical mechanical ice detachment treatments. Functionalized TiO2 coatings, applied using the suspension plasma spray (SPS) technique, have been shown to be robust and to have dual-scale characteristics in an ice accretion analysis. In this study, the icephobicity and mechanical durability of a novel duplex coating consisting of polytetrafluoroethylene (PTFE) solid lubricant films on TiO2-coated substrates were evaluated. Notably, various amounts of PTFE were applied on top of the TiO2 coating to identify the ideal quantity required to obtain optimal icephobic properties. Ice was generated in an icing wind tunnel, and the amount of accreted ice was evaluated to assess the anti-icing properties. Wettability parameters, including static water contact angle and contact angle hysteresis, were measured to determine the water mobility and surface energy. Ice shear adhesion to the PTFE-TiO2 duplex coating was measured using a custom-built test rig. The mechanical durability was assessed by measuring the ice shear strength for almost twenty icing–deicing cycles, and after five cycles, the roughness parameters and images taken from the surface of the samples were compared. The combination of PTFE solid lubricant film and TiO2 coating reduced ice adhesion by 70%–90% compared to that of a bare aluminum substrate (reference material). Additionally, the results showed that the application of a uniform layer of PTFE solid lubricant film on dual-scale TiO2 coating significantly reduced ice adhesion and maintained mechanical durability for 25 deicing cycles, making this combination a promising candidate for deicing approaches.

Fabrication and properties of n-SiO2/m-SiO2/PU superhydrophobic coatings

In order to eliminate the adverse effects of icing on the surface of mechanical devices such as power transmission cables and wind turbine blades due to low temperature, nano-silica (n-SiO2) and micron-silica (m-SiO2) modified by silane coupling agent were blended with a mass ratio of 5:1 and subsequently compounded with polyurethane (PU) to obtain n-SiO2/m-SiO2/PU superhydrophobic coatings. It is shown that the tight bonding of m-SiO2 with PU avoids the cracking of the coating due to the agglomeration of n-SiO2 and improves the stability of the coating. n-SiO2 makes the surface of n-SiO2/m-SiO2/PU coating form a dense and rough structure, which increases the air-liquid contact area by trapping more air. The contact angle reached 158.10° at a low filling ratio(40 wt%), indicating that the prepared n-SiO2/m-SiO2/PU coating has excellent superhydrophobic properties. The superhydrophobic n-SiO2/m-SiO2/PU coating is very helpful in solving the low-temperature icing problem of outdoor power and wind equipment in rain and snow.

An experimental study of rime ice accretion on bundled conductors

The dynamic ice accretion process on bundled electrical power conductors and icing-induced effects on the aerodynamic forces acting on the conductors were examined experimentally. An Icing Research Tunnel was used to generate a typical atmospheric rime icing condition experienced by power transmission cables. Two pieces of Aluminum-Conductor-Steel-Reinforced (ACSR) cables were mounted in the icing wind tunnel with different spacing and angular displacements with respect to the incoming airflow. While ice accretion was found to take place primarily on the frontal surfaces of the bundled conductors, the accreted ice layers resembled well the twisted outer strands of the ACSR conductors. Averaged outer profiles of the iced conductors were elliptical with the semi-minor axis being the radius of the conductors and the semi-major axis passing through the foremost frontal points of the accreted ice layers. The icing process on the windward conductor was almost unaffected by the existence of the leeward conductor. The ice accretion and resultant aerodynamic force acting on the leeward conductor were found to vary significantly, depending on the spacing and angular displacements between the bundled conductors. The windward conductor was found to induce a “shadowing effect” by intercepting airborne supercooled water droplets to prevent them from impinging onto the leeward conductor, resulting in much less ice accretion and smaller aerodynamic drag acting on the leeward conductor. The aerodynamic force measurements were correlated with the acquired ice accretion images and wake flow field around the bundled conductors to elucidate the underlying physics.

Lightweight Copper–Carbon Nanotube Core–Shell Composite Fiber for Power Cable Application

The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 106 S/m with an ampacity of 0.18 × 105 A/cm2. The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm3 and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables.

Protection scheme for multi-terminal HVDC system with superconducting cables based on artificial intelligence algorithms

This paper presents the development of a novel data-driven fault detection and classification scheme for DC faults in multi-terminal HVDC transmission system which incorporates superconducting cables and modular multi-level converters. As the deployment of superconducting cables for bulk power transmission from remote renewable generation is progressively increasing in the future energy grids, many fault-related challenges have been raised (i.e., fault detection, protection sensitivity/stability). In this context, the applications of Artificial Intelligence techniques have started to be considered as a powerful tool for the development of robust fault management solutions. The proposed artificial intelligence-based method utilizes local current and voltage measurements to detect and classify all types of faults on the DC cables and DC buses, without the requirement of measurements exchange among different DC substations. The performance of the proposed scheme has been assessed through detailed transient simulation analysis and the results confirmed its effectiveness against a wide range of fault conditions (i.e., various fault types, fault locations and fault resistances). Furthermore, the feasibility of the developed scheme for real-time implementation has been validated using real-time software in the loop testing. The results revealed that the proposed algorithm can correctly, and within a very short period of time (i.e. less than 2 ms) detect and classify the faults within the protected zone and concurrently remain stable during external faults. Additionally, the generalization capability of the algorithm has been verified against influencing factors such as the addition of noise, highlighting the robustness of the presented scheme.

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.

Ultrastrong Carbon Nanotubes–Copper Core–Shell Wires with Enhanced Electrical and Thermal Conductivities as High-Performance Power Transmission Cables

Demands for high-performance electrical power transmission cables continue to rise, especially for offshore power transmission, electric vehicles, portable electronics, and deployable military applications. Carbon nanotubes (CNTs)-Copper (Cu) core-shell wire is regarded as one of the best candidate material systems for transmitting electricity and thermal energy. In this study, a facile and robust approach was developed to enhance the CNT-Cu interfacial interactions. This approach consists of a substrate-enhanced electroless deposition step for Cu pre-seeding and thiol functionalization. Benefiting from the thiol-activated CNT surface and Cu seed deposit, the CNTs-Cu core-shell wire forms a densely packed Cu shell with a void-free CNT-Cu interface. Consequently, the CNTs-Cu core-shell wire possesses (1) superior specific strength (eightfold stronger), (2) 30% higher specific conductivity, (3) 120% higher specific ampacity, and (4) an impressive 110% higher thermal conductivity compared with pure Cu wires. Moreover, this composite wire still maintains its structural integrity and electrical properties over 600 cycles of the fatigue bending test, rendering this system an excellent candidate for high-performance electrical cable and conductor applications.

Experimental and numerical investigations of the ultimate strength of two subsea power-transmission cables

Integration of renewable energies into existing grids must be safe and reliable including the subsea power-transmission cables. Therefore, this paper determines the purely mechanical ultimate strength of a DC and an AC power transmission cable under axial load. Aspects concerning the electrical functionality of these cables are outside the scope of this paper and failure of the cable is defined as rupture of the cable following ultimate strength. At first, the individual components of the cable are tested to obtain the engineering stress strain relationships to derive material model data for the numerical simulation of the components and cables. The latter is compared to full-scale experimental results of the power transmission cables. Very good comparison of the numerical and experimental ultimate strength of the cables was achieved with the presented straightforward procedure.

Research on Urban High Voltage Power Network Harmonic Transfer and Emission Level

With the rapid growth of urban power transmission cable scale, the harmonic pollution in the high-voltage power grid is more transmitted to other power grids of different voltage levels, which makes the harmonic transmission more complicated, increases the harmonic emission level, and makes it difficult to quantitatively analyze and study the allowable value of users’ electrical pollution emission. Therefore, in this paper, by establishing the harmonic conduction model of the urban high-voltage power grid and considering the equivalent circuit of transformer and transmission cable in the urban power grid, the parameters of transmission cable harmonic transfer coefficient and the allowable emission value of power quality pollution of the urban power grid are deduced and quantitatively analyzed. Then the harmonic transmission and mutual influence of urban power network harmonics in power transmission cable are analyzed through examples, which is helpful to determine the allowable value of harmonic pollution emission scientifically and reasonably.

HVDC gas-insulated equipment for future bulk power delivery

Entering the 21st century, the world's electric power structure will undoubtedly be advanced to one based on the rapidly growing, diversified and co-progressive renewable energy from a coal-dominated one. The development of deep- and far-sea offshore wind power is considered one such vital source for the generation of future energy infrastructure in China's 14 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> Five-Year Plan (2021–2025) for the National Economic and Social Development of China. It is estimated that from 2022 to 2025, the newly installed offshore wind power capacity will be increased to more than 300 GW. The investment cost of the offshore platform can be significantly decreased by adopting small gas-insulated switchgear in conjunction with submarine cable, which is a novel strategy to build large-scale offshore wind power stations in the future. Furthermore, the clean energy transmission from south-eastern Tibet to the Greater Bay Area (±800 kV DC power transmission project) faces harsh natural environmental conditions such as snow-capped mountains and uninhabited areas. The gas-insulated power transmission line provides a superior option instead of the traditional outdoor power transmission lines and cables.

Aerospace Environmental Challenges for Electrical Insulation and Recent Developments for Electrified Aircraft.

The growing trend towards high voltage electrical assets and propulsion in the aeronautics and space industry pose new challenges in electrical insulation materials that cannot be overlooked. Transition to new high voltage electrified systems with unprecedented high levels of voltage, power, and efficiency must be safe and reliable. Improvements in both performance and safety of megawatt power systems is complicated because of the need for additional power transmission wiring and cabling and new safety requirements that have the potential of making the resulting systems heavier. To mitigate this issue, novel lightweight materials and system solutions are required that would result in lower specific weights in the insulator and conductor. Although reduced size and weight of system components can be achieved with new concepts, designs, and technologies, the high voltage (≥300 V) operation presents a significant challenge. This challenge is further complicated when considering the extreme operating environment that is experienced in aircraft, spacecraft, and targeted human exploration destinations. This paper reviews the extreme environmental challenges for aerospace electrical insulation and the needs associated with operating under high voltage and extreme environments. It also examines several recently developed robust lightweight electrical insulation materials that could enhance insulation performance and life. In aerospace, research must consider mass when developing new technologies. The impact of these recent developments provides a pathway which could enable next generation high altitude all electric aircraft, lightweight power transmission cables for a future sustained presence on the Moon and missions to Mars using HV propulsion, such as spacecraft with Nuclear Electric Propulsion systems.

On the Expediency of Laying Cable Power Lines with a Voltage of 6–35 kV Outside Settlements Instead of Overhead Power Lines

. It is noted that at present, 10 and 35 kV overhead power transmission lines are being laid outside the settlements of the Republic of Belarus on reinforced concrete vibrated (10 kV) and centrifuged (35 kV) poles that are characterized by low reliability and damaging the environment (on account of alienation of land for poles, the need to make a wide clearing for laying in the forest, obstructions by poles and wires of lines to the operation of agricultural machinery, the danger of electric shock to personnel and the public). It is possible to avoid these disadvantages if, instead of overhead lines, power transmission cables with cables insulated by cross-linked polyethylene are used which are characterized by a very low failure flow parameter. Contrary to the prevailing opinion about the higher cost of cable power transmission lines compared to overhead ones of the same rated voltage, it turned out that, taking into account reliability, the cost of electricity lost in the lines for a year, damage to the environment and to the power system caused by the need to perform more expensive emergency repairs (as compared to a planned one), laying cable lines with three-core and single-core cables of a voltage of 10 and 35 kV instead of overhead cables outside the populated area is fairly justified. In this connection, the laying of three-core cables is more preferable. It should be also borne in mind that with an increase in the length of cable lines, the capacitive earth fault current increases, to compensate for which additional devices are needed to be installed in power centers, viz. arc-extinguishing reactors or resistors, accounting for the cost of which (up to 22 % of the cost of one kilometer of cable line) does not significantly affect the conclusions we have drawn regarding the effectiveness of using 6–35 kV cable power lines in an unpopulated area instead of overhead ones, however.