Conductor Cross-section Research Articles

Full 3D thermal-hydraulic and electric modelling of quench propagation in HTS conductors

Abstract A fully three-dimensional multi-physics model to simulate quench propagation in high temperature superconducting (HTS) conductors for fusion applications is presented. It accounts for thermal, electric and fluid dynamics throughout the entire transient. The need for high-fidelity models for quench simulations comes from the bulky layouts of many HTS conductors that are being proposed. The model is then validated against experimental data, showing a good agreement on all the relevant quantities (local voltages and temperatures). It is shown that the detailed model improves the quality of the agreement with the measured data with respect to more simplified models. It also allows an insight on the temperature distributions in the conductor cross-section, which can be relevant for the interpretation of experimental data as well as to support the design of quench detection strategies which rely on local temperature variations.

Enhanced Joule heat release at surface irregularities

The heat release that occurs in a cylindrical conductor carrying an alternating current is analyzed for the cases when the conductor has axisymmetric surface irregularities of one of three types: local bumps, local pits, and sequences of alternating bumps and pits (wavy irregularities). The magnetic field and current density distributions over the conductor cross section have been simulated. The simulation parameters were chosen to match the conditions of experiments on the generation of strong magnetic fields. However, due to the analysis of the initial heating stage, the problem is solved neglecting the temperature dependence of the resistivity of the material. A multiple increase in heat release power in the vicinity of a surface irregularity has been revealed for the three types of irregularities.

Experimental void fraction measurement approach of small channel two-phase flow

This investigation presents a novel experimental approach for assessing void fraction parameters in two-phase flows within microchannels. The study critiques the conventional impedance methods that utilize alternating current (AC) for void fraction measurements, highlighting the inherent drawbacks such as ground capacitance interference and non-uniform current distribution. To circumvent these issues, the research introduces the use of direct current (DC), which ensures a homogeneous distribution across the conductor's cross-section, as a more reliable alternative. Termed the "Direct Impedance Method," this technique employs DC to enhance the accuracy of void fraction measurements. The study explores various geometric configurations of full-ring and half-ring electrodes, both vertical and horizontal, within a microchannel of 500 μm diameter. An empirical formula is derived to calculate the void fraction from the electrical data obtained. High-speed imaging at 4000 frames per second supplements the method by providing visual confirmation of the flow patterns. The comparative analysis of the direct impedance method and image processing using the homogeneous theoretical model reveals a deviation of approximately 2 %–10 % for the slug and annular flow pattern. In contrast, the deviation is more for the bubble pattern. The results affirm that the Direct Impedance Method is a cost-effective and reasonably precise technique for small-channel applications. Its accuracy is inversely proportional to the channel diameter, rendering it unsuitable for channels larger than 2 mm. The method's low construction cost further enhances its practical appeal.

Precursor-Derived Sensing Interdigitated Electrode Microstructures Based on Platinum and Nano Porous Carbon.

Interdigital electrodes were prepared using nanoimprint lithography and piezoelectric inkjet printing. These processes are simpler and more cost-effective than the industrially used electron beam lithography because of their purely mechanical process step. For the investigation of material dependence, platinum as well as carbon electrodes were fabricated. Afterwards electrodes with various line widths and spacings were tested for the application as a chemiresistive sensor for ferrocenyl-methanol and the influence of the gap-width and conductor cross-section on the sensitivity was investigated. The general suitability of the systems for the production of such structures could be confirmed. Structures with a limit of detection (LOD) down to 1.2 μM and 35.9 μM could be produced for carbon and platinum, respectively, as well as a response time of 3.6 s was achieved.

Redesign of the electrical power and lighting network at ice cream parlor located in the city of Quito

Abstract This article proposes the redesign of the electrical power and lighting network in an Ice Cream Parlor located in the city of Quito to ensure continuity in the electrical service and a luminous level according to the UNE 12464.1 Standard, established in the country. For this purpose, a survey of all the electrical load installed in the organization was carried out, where the nominal parameters of each equipment were identified with the help of the nameplate of each one of them. Using the specifications of the Ecuadorian Construction Standard (NEC) and the data obtained from the electrical load survey, five (5) circuits for outlets were proposed, considering a possible expansion of small equipment and the ten (10) maximum outlets established by the aforementioned standard. Additionally, four (4) circuits were proposed to feed the power load. With respect to the lighting network, the DIAlux software is used to determine the number of lamps, luminaires and their location to comply with the luminous level indicated. Therefore, it was necessary to propose six (6) circuits in order not to exceed the fifteen (15) lighting points established by the NEC. For each circuit, the following was calculated: conductor cross section, overcurrent protection, type of insulation and the diameter of the corresponding conduit to protect the conductors. Finally, quotations were made for the materials required for the implementation of the project. From these, an organization is selected, based on the availability of the necessary materials, their cost and accessibility, compared to other suppliers. The total amount of the proposal is US$2,518.24.

Development of Mathematical Model for Determining The Relative Power Loss of Power Transmission Lines

One of the many problems faced by the power transmission and distribution network in our country is the problem of reducing the power losses during power transmission. This article presents the results of a study on technical losses as a component of intensity losses. In this study, a mathematical model was developed to determine the relative power loss, taking into account both load and conditional-constant losses. For the selected research object, the relative power loss was determined using the mathematical model developed above using MATLAB software, and the results were displayed graphically, and corresponding appropriate conclusions were drawn. It can also be seen from the calculation results that when the cross-section of the line conductor increases or the resistance of the conductor decreases, the loading current increases and the relative power loss can become a smaller value.

Correlating critical current density, quench protection, relaxation time and entropy in superconductors after disturbances—Intermediate summary

<p>This paper summarizes results recently obtained from simulation of transient temperature excursions in filamentary and thin film superconductors. Under multi-component heat transfer in the complicated conductor cross sections and materials composition of present High Temperature Superconductors, numerical, Finite Element and Monte Carlo simulations are applied to solve Fourier’s differential equation with high spatial and temporal resolution. The overall aim was to encircle the quench problem in superconductors and to provide new stability criteria from correlations between superconductor critical current density, density of electron pairs, and relaxation time and entropy. Relaxation, correlation and entropy analysis presented in this paper extends the spectrum of standard methods to avoid quench to a new tool. As results, quench starts always locally, and as a highlight of this investigation, a second “critical” temperature, <em>T<sub>Quench</sub></em>, has been identified that with high probability exists below standard critical temperature. Entropy is the driving force for relaxation of the superconductor to new equilibrium after a disturbance.<strong></strong></p>

Investigation on the Torsional–Flexural Instability Phenomena during the Bending Process of Hairpin Windings: Experimental Tests and FE Model Validation

Modern electric motors developed for the automotive industry have an ever higher power density with a relatively compact size. Among the various existing solutions to improve torque and power density, a reduction in the dimensions of the end-windings has been explored, aiming to decrease volume, weight, and losses. However, more compact end-windings often lead to complex shapes of the conductors, especially when preformed hairpin windings are considered. The rectangular cross-section of hairpin conductors makes them prone to deviating out of the bending plane during the forming process. This phenomenon, known as torsional–flexural instability, is influenced by the specific aspect ratio of the cross-section dimensions and the bending direction. This study focuses on understanding this instability phenomenon, aiming to identify a potential threshold of the cross-section aspect ratio. The instability makes it difficult to predict the final geometry, potentially compromising the compliance with the geometric tolerances. A finite element model is developed to analyse a single planar bend in a hairpin conductor. Various cross-section dimensions with different aspect ratios are simulated identifying those that experience instability. Moreover, an experimental campaign is conducted to confirm the occurrence of instability by testing the same single planar bending. The experimental data obtained are used to validate the finite element model for the tested dimensions. The aim is to provide designers with a useful tool to select hairpin geometries that are more suitable for the folding process, contributing to successful assembly and improving the overall design process of preformed hairpin conductors.

Enhancing Electrical Distribution System Efficiency: A Software Tool Design for Conductor Cross-Section Optimization With TLBO Algorithm

In radial distribution networks with many separate branches and sections, it is very difficult to calculate the optimum conductor cross-section. This work introduces a new tool for optimizing conductor cross-sectional area in electrical distribution systems by utilizing the Teaching-Learning-Based Optimization (TLBO) algorithm. The tool can optimize the conductor crossection of the multisection, branching distribution systems. The maximum current carrying capacity constraint is taken into consideration when formulating the objective function to choose the ideal conductor size for each network segment. The optimal conductor sizes are determined by both desired percent voltage drop and current carrying capacity of the conductor. By calculating the currents drawn from the line segments in advance, the search space of the optimization algorithm is narrowed. MATLAB and Excel were used to determine the ideal conductor size. The conductor, which is chosen using the suggested method, will preserve appropriate voltage levels in radial distribution systems while optimizing the overall savings in conducting material and energy loss costs. The outcomes show that the optimal selection of conductor problem can be solved by the TLBO algorithm in a practical and effective manner. Results of testing the suggested tool on a radial distribution system are noteworthy.

Thermal State Effects on Potential Augmentation of the Ampacity of a Medium Voltage Underground Cable in Power Distribution: A Case Study

Thermal State Effects on Potential Augmentation of the Ampacity of a Medium Voltage Underground Cable in Power Distribution: A Case Study

Comparative Study on the Ampacity of 500 kV Single-Core and Three-Core Submarine Cable

Submarine cable is an important equipment for data communication and power transmission in power systems, which has a complex laying environment. According to its structure, submarine cables can be divided into two types, single-core cables and three-core cables. In practical engineering, cable selection is crucial to ensure the safe and stable operation of the cable and reduce the cost. The present work compares the ampacity of 500 kV single-core cable and three-core cable with the same conductor cross-section area under certain laying conditions. And the temperature rise situation of the three-core cable and the single-core cable is compared under the application of the same current. The results reveals that the ampacity of the three-core cable is less than one-core cable under certain laying situations. And the maximum ampacity reduction of the three-core cable is 28.96%. Furthermore, the highest temperature rise point of the three-core cable is the air section of the J-tube, and the maximum temperature reaches 130.07°C.

A Comparative Study of Finite Element Method and Hybrid Finite Element Method–Spectral Element Method Approaches Applied to Medium-Frequency Transformers with Foil Windings

This study aims to improve the computational efficiency of the frequency domain analysis of medium-frequency transformers (MFTs) with the presence of large clearance distances and fine foil windings. The winding loss and magnetic energy in MFTs in the medium-frequency range are calculated utilizing a finite element method (FEM) using common triangular and alternative rectilinear mesh elements. Additionally, in order to improve the computational efficiency of the calculations, a spectral element method (SEM) is coupled with a FEM, thus creating a hybrid FEM–SEM formulation. In such a hybrid approach, the FEM is used to calculate the current density distribution in the two-dimensional (2D) cross-section of the foil conductors to achieve reliable accuracy, and the SEM is adopted in the nonconducting clearance distances of the winding window to reduce the system of equations. The comparative analysis of the calculated resistance and reactance of the under-study models showed that the FEM with rectilinear mesh elements and the FEM–SEM model outperformed the FEM with triangular mesh elements in terms of accuracy and computational cost. The hybrid FEM–SEM model enables a reduced system of equations for modeling the electromagnetic behavior of MFTs. This research provides valuable insights into both the computational approaches and meshing challenges in the analysis of MFTs and offers a foundation for future research on the design and optimization of MFTs.

Fault current limiter based on high temperature superconductors

High Temperature Superconductors (HTS) made the Superconducting Fault Current Limiter (SFCL) a reality in power electric grids. Resistive SFCL, which is the subject of this article, is based on a unique property of superconductors to quench from a non-dissipative to a high dissipative state above a given current. SFCL is an attractive response to the poorly solved problem of fault currents in power electric grids and makes it possible to enhance the security and quality of electricity, something that matters more than ever. Liquid nitrogen cryogenics – which is possible thanks to HTS- makes the cryogenics user friendly. In-field SFCL operations confirm this. Second generation (2 G) HTS materials or Coated Conductors suit well to SFCL. Due to its high interest, SFCL has been the subject of a great deal of research and development. In terms of Technology Readiness Level (TRL) it reaches 8 with several in grid test experiences.Here a short history of SFCL is presented with a highlight about Curl 10, Ampacity and SuperOx devices. The two major locations in the grid are reported: grid coupling and feeder protection. The quench phenomena is described in a bit more detail before the basic design (length and cross section) is presented. The design is primarily thermal, considering two extreme operations: fault with very high prospective current (clear short-circuit) and fault with prospective current close to the minimum runaway current along the length. This operation is called the hot spot one. It is due to the intrinsic variation of the critical current along the length and to the low Normal Zone Propagation Velocity (NZPV). The cost of the superconducting conductor is given, showing no bottleneck for an economic development. All the more it is still possible to lower the cost with some developments. This article ends with two real advances presently underway: Current Flow Diverter (CFD) and Sapphire substrate superconducting 2 G tape. CFD aims to increase the NZPV, to still further secure the operation and to reduce the conductor cross section. The use of sapphire substrates allows to reduce significantly the length of the design.

Electromagnetic interference and the effect of low-voltage protective measures at electric vehicle charging stations

The nominal power of electric vehicle charging stations or charging parks is constantly increasing. Most of the users are ordinary persons and handle such equipment with a rated power of several 100 kW. Until now, equipment with such power ratings was only common in electrical operating facilities such as industrial plants where the users are at least instructed and protective measures are specified. If ordinary persons handle equipment with such power ratings in the field, the question arises as to whether the conventional safety goals are met in the event of an electrical fault. The consideration is: If the power increases so much, it can be assumed that the short-circuit power and thus the fault current increase and so does the risk of a dangerous electric shock. In this contribution, calculations of line-to-earth short-circuits on the low-voltage AC side of the three-phase system and their effects in typical configurations of charging stations are carried out. Considering the electromagnetic interference, the calculations provide the fault current and its distribution to determine the electrical potentials during the fault. From this, the (partial) fault voltages and active fault voltages are calculated. Based on the active fault voltage, the expected body impedance and consequently, the body current can be determined. With the body current and the break time of the protection device the risk of electric shock using international standards as guidelines is evaluated. As a result, recommendations for the planning, installation and safe operation of charging stations are given. It turns out that considering certain aspects like the conductor cross-sections or the electromagnetic interference, the risk of electric shock can be reduced to a conventional level. Periodic testing of the electrical system is necessary for safe and reliable operation. For example, follow-on faults due to unintended, improper use by ordinary persons can be prevented. Also, regular inspection of the electrical system is necessary for safe and reliable operation to prevent hazards due to aging or wear. However, it seems challenging to define an installation guideline that applies to all configurations as the boundary conditions vary depending on the type of system, installations in the area of interference and environmental influences.

The Influence of Hot Point on MTU CB Condition at the Pgeli-Giugur 1 Bay Line (PT. PLN Paya Geli Substation)

Local heating that occurs in substation equipment is caused by the current flowing in the conductor due to resistance. The parts that often experience heating are the terminals and connections at the substation, especially between two different metals, as well as the conductor cross-section which decreases due to corrosion. So that part must be considered. As for how to control or check the temperature is done by using thermovision. The heat temperature of the Circuit Breaker (CB) equipment at the Bay line PGELI-GIUGUR1 at Paya GeIi Substation is still in normal conditions where the temperature ranges from 20oC-43oC. But one phase need attention if temperature more than 70oC, it is needed for improvement plans. The temperature difference between the phases of the CB equipment at Bay Iine P. GELI-GLUGUR 1 at Paya Geli Substation has reached condition 5 (five), so it needs serious attention and a repair plan, to avoid short circuits between phases (R, S, T).

Preliminary Multiphysics Modeling of Electric High-Voltage Cable of Offshore Wind-Farms

During manufacture, handling, transportation, installation and operation, mechanical overstress can affect the electrical and thermal properties of the conductor. As the wires in general are made of copper, which is a very plastically deforming material, these stresses will gradually generate plastic deformations of the copper until the wires start to fail. The objective of this article is to study, by numerical modeling (using Comsol and Abaqus), the impact of damage mechanisms on the electrical and thermal properties of a submarine cable phase. The influence of plasticity and gradual copper wire failure on the physical behavior (electric and thermal) of the phase was assessed. The heat differences between a healthy conductor vs. a damaged one (either deformed plastically and/or with failed wires) derived from the numerical model may be an accurate indicator of the level of damage of wires, thus furthering advanced warning before being obliged to stop the exploitation because a mandatory heavy maintenance of the cables must be scheduled. Note that this can also be achieved by using an optical fiber as a sensor for structural health monitoring. This study will then make it possible to evaluate the impact of the modification of the resistance on the thermal behavior of the cable. All of these simulations will be carried out on one phase of a 36 kV 120 mm² copper submarine cable. Colloquially these are called “copper cables”, meaning cables with Cu conductors (120 mm2 is the smallest conductor cross-section for array cables, which are usually 3-phase cables).

Mathematical model for salient-pole synchronous motor field-coil calculation and optimization

To optimize the parameters of the salient-pole synchronous machine field-coil and achieve specified technical and economic characteristics, an optimization problem with restrictions, which belongs to the class of nonlinear programming problems, was solved. Mathematical model for salient-pole synchronous motor field-coil calculation and optimization, an algorithm and a computer program were created. The mathematical model for calculation and optimization of salient-pole synchronous machine field-coil provides a possibility to design a single-row field-coil winding based on known dimensions under the following restrictions: the minimum distance between the coils of adjacent poles must not be less than the permissible value, the temperature of the coil above the ambient temperature must not be greater than the maximum permissible for the chosen insulation class of the value of the coil, according to the conditions of single-row coils manufacturing, conductor cross-section area should not be greater than the permissible value, and the ratio of the width of the conductor to its height should be within certain limits, the dimensions of the conductor should correspond to standard values. The optimization criterion (objective function) is the copper consumption or cost of the coil, the consumption or cost of pole core steel, power losses in the coil, the total cost of copper and pole steel, the total costs of machine manufacturing and its operation. The choice of the optimization criterion depends on the purpose of the machine and the requirements placed on it. In this problem, each of these criteria is a function of one variable - the height of the field-coil.

Impact of the Short-Circuit Current Value on the Operation of Overhead Connections in High-Voltage Power Stations

This paper focuses on determining the effects of short-circuit current values on the operation of high-voltage substations. The analyses performed focused on the dynamic and thermal effects on the short-circuit current for different input data configurations. The analyses of the dynamic effects of short-circuit current were performed in two ways. First, calculations were executed using the procedures contained in “IEC 60865-1:2012 Short-circuit currents, calculations of the effects of short-circuit currents. Part 1: Definitions and calculation methods”. Analytic calculations were accomplished for different values of the initial three-phase short-circuit current, the type of short circuit, the static tension force of the conductors, the stiffness of the structure and the methods of attaching the lashing chains. Secondly, the same analysis was performed using PRIMTECH 3D software. The connections were modeled in computer software, for which the calculations were implemented according to normative recommendations. After obtaining the results, an analysis was performed using the model based on the input data. Performing the analysis in two ways made it possible to compare the results with each other and develop conclusions. An analysis of the thermal effects of the short-circuit current was also provided. The results of the calculations showed that the choice of conductor cross sections according to the value of the initial short-circuit current was correct. Particular attention has been paid to rigid conductors and flexible conductors, which are directly affected by the short circuit and have an impact on the selection of the complete equipment for the high-voltage switchgear.

Research on the evaluation method and improvement measures for the operational efficiency of high-voltage DC power transmission

This paper analyzes the calculation principle of DC transmission line loss and economic current density, specific to the loss of each component of the HVDC system, studies the evaluation method of AC/DC transmission line operation efficiency that can reflect the characteristics of long-distance, large-capacity, high-voltage and clean environmental protection of DC transmission, including economic benefit indicators and environmental benefit indicators, analyzes the key factors affecting the operation efficiency of transmission lines, and proposes measures to reasonably improve the operation efficiency of DC transmission, it includes four measures to improve the transmission voltage level, optimize the power flow of each DC transmission system, select appropriate conductor cross-section, and reduce line maintenance costs.

Семейство математических моделей для описания движения металлических проводников в электромагнитном поле

The modeling of metal conductors acceleration in an electromagnetic field in a two-dimensional approximation is executed. A family of mathematical models for describing the motion of a body is presented: a model of a thermoelastoplastic body (for the case of large deformations), a model of a viscous compressible liquid and a mixed model that includes two previous models for different phase states of matter. A mathematical model of electromagnetic processes is presented, which allows to ensure the flow of total currents along the cross-sections of conductors. Numerical algorithms based on the finite element method are presented. The described models are used to solve the problem of accelerating the aluminum cylindrical shell to a speed of about 8 km/s. The results obtained for different models were compared with each other, as well as with known calculated and experimental results published in the literature.