Structural Analysis of the US ITER ECH Transmission Line System

The measurement of the power injected by the electron cyclotron heating (ECH) system in the DIII-D tokamak is a critical requirement for analysis of experiments, for tuning the gyrotrons for maximum power and efficiency, for tracking long-term operational trends, and for providing a warning of problems with the system. The ECH system at General Atomics consists of six 110-GHz, 1-MW-class gyrotrons. The radio-frequency (rf) power generated by each gyrotron is determined from calorimetry, using the relevant temperature and flow measurements from the cooling circuits of the cavity, matching optics unit, and dummy loads (DLs). The rf pulse length and time dependence are measured using an rf monitor at the first miter bend in the transmission line. The cavity power loading measured directly gives the generated rf power using a previously determined relationship between cavity loading and rf production. The direct measurement of the efficiencies of four of the transmission lines was performed using a high-power DL placed alternately in two positions of each DIII-D waveguide line, at accessible points close to the beginning and the end of each line. Total losses in the transmission lines range from 21.2 to 30.7%. Experimental results are compared to theoretical predictions of the performance of the components and waveguide lines.

The ITER Electron Cyclotron Heating (ECH) system consists of transmission lines made up of individual sections of evacuated, aluminum, circularly corrugated waveguides. The high-intensity beam of electromagnetic radiation, necessary for plasma heating, heats the waveguides and other components in the transmission lines causing the lines to expand and contract. To maintain the structural integrity and the required straightness in the transmission lines, expansion units have to be incorporated into the ECH transmission line system.Calculations of several models of expansion units have been completed to evaluate the effect of the design and materials on the functionality of the expansion unit. Models have been evaluated assuming three different expansion ranges and several different materials.

The Electron Cyclotron Heating (ECH) system on DIII-D consists of six 110 GHz gyrotrons with 6 MW installed power for pulses limited administratively to 5 s in length. The transmission coefficient is better than -1.1 dB for four of the transmission lines, close to the theoretical value. A new depressed collector gyrotron was recently installed and is injecting up to 720 kW of power into DIII-D during 2013 tokamak operations. Three of the four dual waveguide launchers, which can steer the rf beams ±20 degrees both poloidally and toroidally, were used for real-time neoclassical tearing mode control and suppression with increased poloidal scanning speed up to 60 deg/s and positioning accuracy of the beams of ±2 mm at the plasma center. The ECH capabilities on DIII-D are being steadily updated, leading to increased experimental flexibility and high reliability of the system. In the past year the ECH system reliability reached 87%, for 2352 successful individual gyrotron shots into DIII-D. Planning is under way for the addition of two new depressed collector gyrotrons, one at 110 GHz, 1.2 MW and another at 117.5 GHz, 1.5 MW generated power, both of which are being manufactured at Communications and Power Industries (CPI).

Summary form only given. During the last years electron cyclotron heating (ECH) has proven to be one of the most attractive heating schemes for stellarators, as it provides net current free plasma start up and heating. Both, the stellarator Wendelstein 7-X (W7-X), which is under construction at IPP-Greifswald, Germany, and the ITER tokamak, which will be built at Cadarache, France, will be equipped with a strong EC-heating and current drive system. Both systems are similar in frequency and have CW (continuous wave) capability (140 GHz, 10 MW for W7-X and 170 GHz, 24 MW for ITER). The commissioning of the ECH plant for W7-X is well underway, the status of the project and first integrated full power test results from two modules are reported and may provide valuable input for the ITER plant. The ten gyrotrons at W7-X are arranged in two sub-groups symmetrically to a central beam duct in the ECH hall. The RF-wave of each subgroup is combined and transmitted by a purely optical multi-beam waveguide transmission line from the gyrotrons to the torus. The combination of the five gyrotron beams to two beam lines each with a power of 5 MW reduces the complexity of the system considerably. The single-beam- as well as the multi-beam waveguide mirrors and the polarizers have been manufactured. Cold tests of a full size uncooled prototype line delivered an efficiency exceeding 90%. The microwave power will be launched to the plasma through ten CVD-diamond barrier windows and in-vessel quasi-optical plug-in launchers allowing each 1 MW RF-beam to be steered independently. The polarization as well as the poloidal and toroidal launch angle can be adjusted individually to provide optimum conditions for different heating and current drive scenarios.

Detection of transmission line is an important and challenging topic in low altitude flight. Different from the traditional transmission line detection method, in which the transmission line is detected based on the straight line, in order to extract the transmission line more completely, this paper proposes a new algorithm of transmission curve detection based on the morphological relation of finite element under the sky background. In the process of image processing, firstly, the whole sky background is extracted, and the line segment of the image under the sky background is extracted. Secondly, in the detection process, according to the idea of finite element, multiple groups of transmission line targets with certain curvature changes are regarded as composed of multiple groups of local line segment pairs. Using the morphological characteristics of the finite element line segment pairs of transmission line, different from other linear targets, line segment screening is carried out to remove the interference of pseudo linear targets. Finally, the finite element line pairs with obvious collinear characteristics are connected by collinear conditions to get the complete extracted transmission line. The experimental results show that this algorithm can detect the transmission line in the field of view and extract them completely.

The need to supply the demand for electricity of large urban centers and large industrial customers has challenged the planning and design of 69kV and 138kV transmission lines. Typically, such voltage levels require conventional infrastructure, with support towers, insulators and cables, sometimes incompatible with the surroundings or with insufficient space for the right of way implementation, considering urban areas. This study aims to accomplish an electrical performance analysis of a proposed design for the compact conductor arrangement aimed to 138kV overhead transmission lines, with reduced distance between phases when compared to conventional 138 kV transmission lines. The proposed arrangement is evaluated under the aspects of lightning performance, switching surges and electric and magnetic field, establishing a comparison with a conventional 138kV overhead transmission line. The proposed compact design permits a reduction of the area occupied by the support structures and transmission line itself, allowing a reduction in the right of way. This provides an alternative solution to conventional overhead transmission lines, which require more space, and to underground transmission lines, whose high investments costs usually hinder their deployment.

The Transmission Line for the SPIDER experiment

The Divertor Tokamak Test (DTT) facility will be built to study a solution to the issue of power exhaust in conditions relevant for DEMO. The Italian DTT tokamak, by coupling to plasma up to 45 MW of additional power, will reach the needed condition of power flow to the divertor of 15 MW/m. The selected Heating Systems to achieve this goal are Electron Cyclotron Heating (ECH), Ion Cyclotron Heating (ICH) and Negative Neutron Beam Injector (NNBI). The power will be installed in two stages: a day-1 configuration with a coupled power of 25 MW and a second step where the completion of the 45 MW will be realized in 4 years from the day-1. At first stage 16 MW of ECH power and 4 MW of ICH will be installed, making the DTT plasma dominated by RF heating. The EC system is based on 170 GHz, 1 MW gyrotron, while for the transmission line a Quasi Optical approach has been chosen, with the feature to install the multi- beam mirrors (8 beams on each one) under vacuum. The goal is to reduce the overall losses at ∼10% avoiding atmospheric absorption and selecting the proper polarization for the longest section. The power will be injected into the tokamak using front steering individual antennas and capable to real time steer all the beams for the tasks assigned to EC waves. The first module of the ICH systems will be based on transmitters, capable of a wide frequency range (60-90 MHz), connected, though standard coaxial cables and RF components, to two movable antennas inserted in the equatorial ports of DTT. The selected range is done to exploit different heating schemes. The choice of the antenna type will be based on reliability (i.e. power density) rather than on its performance in term of peak coupled power. This led to choose a two-strap antenna with a power density of 3.5 MW/m2, shaped to fit the DTT scrape-off plasma and with an adjustable radial position. An external matching system is envisaged to cope with fast variation of antenna loading, e.g. due to edge localized modes.

More ice deposits accreted on conductors or ground wires may be shed off when an overhead electric transmission line is responding to shocks initiated by natural ice shedding. Ice shedding causes the global mass, stiffness, and damping of the tower-line system to vary with time, and the successive shedding effect beyond a trigger event has not been taken into account in previous studies due to the lack of an adequate ice detachment model. In this paper, the ice shedding effect induced by initial shocks was considered in finite element (FE) analysis. An ice detachment criterion, in the way of user-defined element rupture subroutine, was implemented into the main commercial nonlinear FE program ADINA, making it possible to consider the induced-ice-shedding effect numerically. The incremental FE form of the system’s governing equations of motion is presented where the variations in the mass and stiffness matrices of the system are taken into consideration. Taking a transmission line section following natural ice shedding as a case study, the results indicate that neglecting successive ice shedding underestimates the adverse influence of natural ice shedding. The proposed method can help to improve the design and evaluation of transmission lines in cold regions and to ensure their mechanical security.

In the era of Extremely Large Telescopes, the current generation of 8-10m facilities are likely to remain competitive at ground-UV wavelengths for the foreseeable future. The Cassegrain U-Band Efficient Spectrograph (CUBES) has been designed to provide high instrumental efficiency ( > 37%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R > 20, 000 (with a lower-resolution, sky-limited mode of R ∼ 7, 000). With the design focusing on maximizing the instrument throughput (ensuring a Signal to Noise Ratio – SNR– ∼ 20 per spectral resolution element at 313 nm for U ∼ 17.5 mag objects in 1h of observations), it will offer new possibilities in many fields of astrophysics: i) access to key lines of stellar spectra (e.g. lighter elements, in particular Beryllium), extragalactic studies (e.g. circumgalactic medium of distant galaxies, cosmic UV background) and follow-up of explosive transients. We present the CUBES instrument design, currently in Phase-C and approaching the final design review, summarizing the hardware architecture and interfaces between the different subsystems as well as the relevant technical requirements. We describe the optical, mechanical, electrical design of the different subsystems (from the telescope adapter and support structure, through the main opto-mechanical path, including calibration unit, detector devices and cryostat control, main control electronics), detailing peculiar instrument functions like the Active Flexure Compensation (AFC). Furthermore, we outline the AIT/V concept and the main instrument operations giving an overview of its software ecosystem. Installation at the VLT is planned for 2028/2029 and first science operations in late 2029.

The complexity of transient processes during travelling-wave propagation in extra high voltage overhead lines is deter-mined by the fact that many frequency components are presented in the electromagnetic wave front. For the correct analysis of the aforementioned transient processes and for further development of travelling-wave-based relay protec-tion and fault location devices, it is necessary to take into account the parameters of the environment where electromagnetic wave propagation occurs. For the transmission line, these parameters are longitudinal inductance, longitudinal resistance, shunt capacitance and shunt resistive conductance. It is worth mentioning that for a variety of reasons unit-area longitudinal inductance and resistance are the parameters which depend on frequency, thus travelling wave velocity is different for different frequency components of the electromagnetic wave front. The popular researches which address this problem either fail to consider the dependence of overhead line inductance and resistance on frequency or this dependence is considered approximately for the high-frequency range, which can cause significant errors in the transient processes analysis during travelling wave propagation. In view of this, the development of the approach to overhead transmission lines simulation, which will allow both determining the line parameters in a wide frequency range and evaluating steady-state behaviour and transient processes in long-distance transmission lines, arrears relevant. The main research method to establish extra-high voltage transmission line parameters employs the simulation study in COMSOL Multiphysics. A number of assumptions were made in the simulation process: homogeneous soil layer, entire transmission line section and absence of transmission line conductor sag. The usage of finite elements method (FEM) for differential equation solution in the above-mentioned software is also seen as an assumption. The approach to extra-high voltage transmission lines simulation has been offered. This approach consists of the usage of Maxwell’s equations in combination with numerical integration with finite elements method (FEM). Frequency response for transmission line parameters and travelling-wave propagation velocity rate for different frequency components have been obtained. The results obtained can be used in updating of electrical power system models for further research in the relay protection field. The suggested approach will allow evaluating line parameters of other voltage types and obtaining more accurate values of transmission line parameters and travelling wave propagation speed along transmission lines for high-frequency range. The use of these transmission line models will enable to formulate approaches to improve the existing algorithms of travelling-wave-based relay protection and fault location devices.

A two-dimensional finite element multigroup diffusion theory for neutral atom transport in plasmas

Sealing net structures are frequently used as protective devices for newly constructed transmission lines that intersect existing lines. They aim to ensure safety during the construction and operation of the intersecting lines. To explore the wind deflection response characteristics of sealing net structures under wind loads, a model of the sealing net structure was created using ANSYS/APDL software for finite element analysis. This model represents an overhead sealing net structure spanning an existing line. The results obtained from finite element simulations aligned well with the theoretical calculations, indicating the validity of the established finite element model for accurately analyzing the wind-induced response of the sealing net structure. Expanding on this foundation, the study analyzed the impact of various factors on the wind deflection of the sealing net. These factors encompass the span, wind speed, pretension of the catenary cable, wind direction angle, arrangement angle, and method of additional stay cables. The research investigated the influence of these factors on the wind deflection of the sealing net structure. Additionally, a proposal was presented for arranging the closure structure to mitigate wind deflection. This proposal provides valuable guidance for the design and safety considerations of transmission lines and sealing net structures.

The paper describes the use of the finite element method when modelling electromagnetic transients on transmission lines in the time domain. The finite element matrix and vector for single line finite element has been obtained using a weighted residual method and time integration performed by an explicit/implicit mixed procedure on the telegrapher's equations. Together with finite elements that represent electrical elements with lumped parameters, an effective method for transients simulation in electrical networks has been obtained. In cases of nonlinear electric parameters Newton-Raphson procedure has been used. To the best of the authors' knowledge this is the first successful application of the finite elements method to first order telegrapher's equations. The benefits of using finite elements in modelling electromagnetics transients come from the possibility of line parameters modelling, particularly from the possibility of a natural implementation of distributed nature of line parameters.

The simplest way to model overhead line is to use reference specific values. There is no need to carry out time consuming preparation of the initial data in this case. The disadvantage of this method is the averaging of distances between the wires. In addition, in industrial power supply systems with high load density the cross-section of conductors is often overestimated to ensure the required reliability and redundancy. This leads to the fact that wires which specific parameters are determined for their use in a 220 kV network are used in a 110 kV. 110 kV transmission lines have significantly smaller distances between phases, compared to 220 kV. All this affects the results of calculating parameters of the mode when using the reference specific electrical parameters of the transmission line. This is especially important when performing fault location calculations of the single-phase short circuit mode in a 110 kV network. For such calculations, it is necessary to introduce the actual location of the conductive elements of the power transmission line. The most convenient for these purposes is the method of phase coordinates. However, it must be borne in mind that the industrial power supply scheme can contain a large number of elements. To reduce the computation time the author of this article had proposed a hybrid equivalent circuit for a single-circuit power transmission line, introducing the effect of lightning protection cable and conducting elements alignment. This equivalent circuit could be used in conjunction with a symmetrical comnonents equivalent circuit.