High Power Transmission Lines Research Articles

Method and Mathematical Model of Suppressing Forced Vibrations in Single Conductors of High-Power Transmission Lines

Method and Mathematical Model of Suppressing Forced Vibrations in Single Conductors of High-Power Transmission Lines

Simulation and Theoretical Study on the Mutual Inductance of the B-Dot Used for High-Power Transmission Lines

For the B-dot used for high-power transmission lines, due to its special structure, the current method to obtain its mutual inductance is calibration experiments and there lacks an effective method to estimate its mutual inductance at the design stage. In this paper, the mutual inductance of this kind of B-dot is studied by simulation and theoretical analysis. Through simulation, the frequency response of the mutual inductance is obtained and it is found that the mutual inductance at high frequency which is the main working frequency range of the B-dot is lowest and stable. Through theoretical analysis, the approximate calculation formula of mutual inductance at any frequency is derived. Using the experimental results in previous reference, the theoretical results and the simulation results are verified. The influencing factors of the B-dot’s mutual inductance at high frequency are analyzed. The results show that the number of wire loops, the inner radius of wire loops and the radius of hole are positively related to the mutual inductance, and the height of the center of the wire loops is negatively related to the mutual inductance. Among these four factors, increasing the inner radius of wire loops can improve the mutual inductance more significantly. The work in this paper reveals the physical meaning of the mutual inductance change and provides guidance for the design of the B-dot.

Optimum profiles of trapezoidal grooves in polarizer mirrors for high-power ECRH systems, and the ohmic loss calculation

Two grooved mirrors are normally uses in electron cyclotron resonance heating (ECRH) systems to induce an appropriate polarization in the microwave for efficient plasma coupling in fusion reactors. In the high-power systems, sharp edges of the grooves may lead to an electrical arc discharge and disable further operation, and in the high-frequency systems where the skin depth is smaller than the surface roughness, the high-power transmission may be limited by the resultant ohmic loss. In this work, parametric profiles of rounded trapezoidal- and rectangular-shaped grooves have been designed based on the free space wavelength to find the best profiles that are suitable for the polarizers in the high-power transmission lines at any frequency. Extensive work has been carried out on the optimum ellipticity of the polarization by employing vector theory integrated with numerical simulations. Then the trapezoidal profiles with desired results have been used to model the grooved mirrors for both polarizers and calculated the ohmic loss on the mirrors for a 5-s pulse of 580 kW Gaussian beam at 110 GHz. Effect of the surface roughness has been also involved in the analysis.

EMI radiation of power transmission lines in Malaysia

Background: There has been rising concern amongst the public regarding their home's proximity to high tension power transmission lines. The primary cause of fear is the impact of the electromagnetic interference (EMI) radiation on the nearby occupants' health. Despite the presence of national permissible limits of EMI radiation, there is still lack of information with regards to the EMI radiation of the types of power lines configuration in Malaysia. Methods: The electric and magnetic fields of several selected power transmission lines were simulated using the EMFACDC software program from the recommendation ITU-T K.90. Five types of power transmission lines available in Malaysia are considered. Results: It was found that the simulated electric and magnetic field levels at all the power lines' right of way (ROW) boundary complies with the prescribed exposure limit. However, the electromagnetic fields (EMF) level increases significantly as the separation distance is reduced from 30m. For a more conservative approach, the ROW can be set at 30m across all transmission voltage level and corridor area condition. Conclusion: It can be concluded that Malaysia's power transmission lines are within the prescribed exposure limits. To further minimize the electric and magnetic field level, it is recommended that the residential building should be built at least 30 meters away from the power transmission lines, especially for the 275kV double circuit, 275/132kV quadruple circuit, and 500kV double circuit lines.

EMI radiation of power transmission lines in Malaysia

Background: There has been rising concern amongst the public regarding their home's proximity to high tension power transmission lines. The primary cause of fear is the impact of the electromagnetic interference (EMI) radiation on the nearby occupants' health. Despite the presence of national permissible limits of EMI radiation, there is still lack of information with regards to the EMI radiation of the types of power lines configuration in Malaysia. Methods: The electric and magnetic fields of several selected power transmission lines were simulated using the EMFACDC software program from the recommendation ITU-T K.90. Five types of power transmission lines available in Malaysia are considered. Results: It was found that the simulated electric and magnetic field levels at all the power lines' right of way (ROW) boundary complies with the prescribed exposure limit. However, the electromagnetic fields (EMF) level increases significantly as the separation distance is reduced from 30m. For a more conservative approach, the ROW can be set at 30m across all transmission voltage level and corridor area condition. Conclusion: It can be concluded that Malaysia's power transmission lines are within the prescribed exposure limits. To further minimize the electric and magnetic field level, it is recommended that the residential building should be built at least 30 meters away from the power transmission lines, especially for the 275kV double circuit, 275/132kV quadruple circuit, and 500kV double circuit lines.

Microstrip Bandstop Filter for Preventing Conduction Electromagnetic Information Leakage of High-Power Transmission Line

The research of transient electromagnetic pulse emission monitoring technology (TEMPEST) protection is essential. Based on microstrip bandstop filter (MSBSF), a method to prevent electromagnetic information leakage of high-power transmission lines is proposed in this paper. The MSBSF with a high insertion loss and carrying large current in the frequency of 2.40–2.49 GHz is designed, fabricated, and experimentally measured. The fabricated MSBSF with the insertion loss of 38 dB at 2.41–2.49 GHz can carry a current greater than 10A and withstand a voltage of 1.7 kV. Compared with the traditional electromagnetic interference (EMI) filter, the MSBSF has the advantages of preventing conducted electromagnetic information leakage in the high-frequency bands, carrying greater current subject to higher voltage, and possessing lighter weight. The MSBSF may be used to prevent the leakage of high-frequency electromagnetic information of high-power transmission lines.

Investigation of the curvature distribution for TE01-to-TM11 mode converter

An oversized TE-to-TM mode converter based on waveguide bend structure is designed for high power transmission line. The curvature distribution of the waveguide bend is analyzed and optimized using mode coupling theory. Analysis results show that the curvature near the output port plays a decisive role in the content of the parasitic modes, which indicates that the restriction on curvature far from output port could be relaxed. Therefore, the asymmetric waveguide axis with enhanced curvature near the front end and lessened curvature near the output port will have a high conversion efficiency and a broad bandwidth. Combining the curvature optimization and the phase rematching technology proposed in our preliminary work, the TE-to-TM mode converter realizes a 90 bend with a conversion efficiency over 95% in the range of 26–32.2 GHz (the relative bandwidth over 21%). To verify the designed mode converter, a prototype is manufactured and measured.

Exciting Circular TM11 Mode Using Symmetric Probes Based on Ridge Gap Waveguide

This article proposes a method to excite the TM $_{11}$ mode in circular waveguides. The principle of synthesizing a circular TM mode is deduced based on the electric dipole moment theory first, and the output mode and its purity are analyzed theoretically. Then, a mode conversion scheme to convert the rectangular TE $_{10}$ into circular TM $_{11}$ mode via a pair of out-of-phase quasi-TEM mode is proposed. In order to achieve the broadband excitation in a compact size, the ridge gap waveguide is used as a medium between the rectangular and cylindrical waveguide. Simulation results present that the proposed exciter has a propagation bandwidth up to 10 GHz in Ka-band with a mode purity over 98%. A prototype is manufactured and measured, and the presence of TM $_{11}$ mode and the mode purity are confirmed by a port radiation pattern measurement. The mode exciter features high mode purity, broad bandwidth, and a compact size, which provides a low-power generator for the research of novel gyrobackward-wave devices and devices in the high-power transmission line.

Experimental Verification of Multipactor Suppression in Microstripline Using High Porosity Surfaces

We report computational and experimental research results confirming that surfaces with porosity exceeding a certain threshold will fully suppress multipactor in parallel-plate microstripline structures, while negligibly perturbing the RF transmission properties. Our research also identified a practical arrangement of nonuniform pores that provided the required high-porosity for multipactor suppression, but with enhanced mechanical rigidity. This alternative layout facilitates the fabrication process using commercially-available manufacturing methods. Porous, multipactor-resistant surfaces can be used in a wide range of high-power components including high-power microwave sources, antennas, filters, and transmission lines (TLs).

EMI radiation of power transmission lines in Malaysia.

Background: There has been rising concern amongst the public regarding their home's proximity to high tension power transmission lines. The primary cause of fear is the impact of the electromagnetic interference (EMI) radiation on the nearby occupants' health. Despite the presence of national permissible limits of EMI radiation, there is still lack of information with regards to the EMI radiation of the types of power lines configuration in Malaysia. Methods: The electric and magnetic fields of several selected power transmission lines were simulated using the EMFACDC software program from the recommendation ITU-T K.90. Five types of power transmission lines available in Malaysia are considered. Results: It was found that the simulated electric and magnetic field levels at all the power lines' right of way (ROW) boundary complies with the prescribed exposure limit. However, the electromagnetic fields (EMF) level increases significantly as the separation distance is reduced from 30m. For a more conservative approach, the ROW can be set at 30m across all transmission voltage level and corridor area condition. Conclusion: It can be concluded that Malaysia's power transmission lines are within the prescribed exposure limits. To further minimize the electric and magnetic field level, it is recommended that the residential building should be built at least 30 meters away from the power transmission lines, especially for the 275kV double circuit, 275/132kV quadruple circuit, and 500kV double circuit lines.

Investigation on current loss of high-power vacuum transmission lines with coaxial-disk transitions by particle-in-cell simulations

Coaxial-disk transitions can generate non-uniform magnetic fields and abrupt impedance variations in magnetically insulated transmission lines (MITLs), resulting in disturbed electron flow and non-negligible current loss. In this paper, 3D particle-in-cell simulations are conducted with UNPIC-3d to investigate the current loss mechanism and the influence of the input parameters of the coaxial-disk transition on current loss in an MITL system. The results reveal that the magnetic field non-uniformity causes major current loss in the MITL after the coaxial-disk transition, and the non-uniformity decreases with the distance away from the transition. The uniformity of the magnetic field is improved when increasing the number of feed lines of a linear transformer driver-based accelerator with coaxial-disk transitions. The number of input feed lines should be no less than four in the azimuthal distribution to obtain acceptable uniformity of the magnetic field. To make the ratio of the current loss to the total current of the accelerator less than 2% at peak anode current, the ratio of the current in each feed line to the total current should be no less than 8%.

Additively manufactured electrodes for plasma and power-flow studies in high-power transmission lines on the 1-MA MAIZE facility.

Power-flow studies on the 30-MA, 100-ns Z facility at Sandia National Laboratories have shown that plasmas in the facility's magnetically insulated transmission lines (MITLs) and double post-hole convolute can result in a loss of current delivered to the load. To study power-flow physics on the 1-MA, 100-ns MAIZE facility at the University of Michigan, planar MITL loads and planar post-hole convolute loads have been developed that extend into the lines of sight for various imaging diagnostics on MAIZE. These loads use 3D-printed dielectric support structures lined with thin foils of either aluminum or stainless steel. The metal foils serve as the current-carrying power-flow surfaces, which generate plasma during the current pulse. The foil thickness (50 µm) and widths (11.5-16mm) are selected to ensure a sufficient linear current density (0.5-0.7 MA/cm) for plasma formation. Laser backlighting (532nm) and visible-light self-emission imaging capture the overall plasma evolution in the anode-cathode gaps, including the gap closure velocities (1-4 cm/μs).

Analysis of Demand Factor for High Speed Railway Power Transmission Line from Load Measurement Data

With the rapid construction of high-speed railway in China and other developing countries, as well as the continuous expansion of its distance and scale, the load of power transmission line along the railway is increased accordingly. However, the existing design standards for power transmission line of high speed railway cannot specify the demand factor for the electrical load supplied by power transmission line, and there is no unified calculation method for the demand factor, resulting in a large difference between the theoretical value and the actual value of transformer capacity and cable section selected for engineering project, which takes huge additional energy penalty from the utility companies. To address the problems and formulate a more accurate selection standard for the load demand factor of high-speed railway power transmission line (HSR-PTL), the demand factor is calculated from the data measured on several typical high-speed railway operating in China. Firstly, the load model of HSR-PTL is proposed. According to the function and characteristics of the several kinds of load in HSR-PTL, each load is classified for load demand modelling. By measuring the load of several typical operating HSR-PTL, based on the proposed model, the value of the required coefficient of each load type based on the measured data is proposed. The calculated demand factor can be applied as an applicable reference for the design of high-speed railway power system.

Thermo-hydraulic and economic aspects of long-length high-power MgB2 superconducting cables

The rising share of renewable energy in the European grid creates a demand for long-length, high-power transmission lines. Superconducting cables represent an attractive option for such connections, offering considerable savings in energy and space for installation. Due to its low cost, the MgB2 superconductor might be an interesting choice, but it requires to be operated at very low temperature. In this paper, a simple thermo-hydraulic model is developed, which allows for a fast assessment of the main dimensions of a four-wall cryogenic envelope around a high-power MgB2 cable as well as the achievable distance between two cooling stations. This model is then expanded to provide the budgetary cost of such a link including the components of the cryostat and the necessary cooling stations. A significant cost reduction as compared to a resistive link can be found for a transmitted power of 6.4 GW. Different optimizations are investigated, which result in further savings.

Theoretical and Experimental Investigations on a Compact and Broadband TE01Oversized Deformed Waveguide Bend

A compact and broadband circular TE01-mode oversized deformed waveguide bend for high-power transmission line is proposed in this article. In order to obtain a circular TE01 mode with high purity output, a deformed waveguide structure, entitled quad-polar waveguide, which can destroy the degeneration between the TE01 and TM11 modes and weak mode conversion inside waveguide bend is introduced. The characterization of quad-polar waveguide and its influence of deformation on the mode spectrum are analyzed. The mode coupling coefficients of quad-polar waveguide are theoretically deduced to investigate the mode conversion inside the waveguide bend. Based on the multimode coupling theory, a broadband oversized waveguide bend with propagation efficiency over 95% from 27.6 to 34.1 GHz is designed. A prototype is fabricated and measured. The average transmission efficiency is over 93% according to the S-parameter measurement. The TE01 mode with high purity output is demonstrated by the near-field test. The high-power performance is investigated by connecting it with a gyrotron traveling-wave tube (gyro-TWT), and the waveguide bend works stably under a maximum output power of 140 kW. In addition to high power and broadband, the proposed waveguide bend features compact, simple structure, and easy to machine.

Design of a $Ku/Ka$ -Band Oversized Waveguide Bend for High-Power Transmission Line

A Ku / Ka -band oversized waveguide bend, transmitting the power of TE01 mode at Ka -band and TE11 mode at Ku -band, is designed for the high-power transmission line. To suppress the generation of parasitic modes, a waveguide bend based on the elliptical waveguide is used to minimize the coupling capacity between the operating modes and the undesired modes. The mode coupling rules inside the elliptical waveguide bend are investigated. The optimized parameters, including the orientation of bend plane, the bend radius, and the eccentricity are chosen according to the analysis results. The calculation results show that the transmission efficiency of the TE01 mode is over 95% from 26 to 32 GHz, while the transmission efficiency of the TE11 mode is over 98.5% from 10 to 20 GHz. To validate the design, a prototype is fabricated and measured. Compared with the calculated results, the measured transmission efficiency has a 4% and 5%–6% drop in the Ka -band and Ku -band due to ohmic loss. The high output mode purity of the waveguide bend is verified by the near-field measurements.

A Circular TE02 Mode Generator With High Purity for Gyro-TWT Study

A new topology to excite circular TE02 mode for studying of gyrotron traveling-wave tube (gyro-TWT) is presented. The mode generator consists of a rectangular TE10 to cross waveguide TE44 mode converter and a cross waveguide TE44 to circular TE02 mode converter. To obtain a high-purity TE02 mode output and make the generator compact, a cross waveguide with sidewall coupling apertures and a novel mode transition section with metal diaphragm are introduced. The proposed mode generator is fabricated and measured. A good agreement between simulation and measurement is obtained, and the 1-dB bandwidth from 28 to 34 GHz is obtained in back-to-back test. The angle-independent transmission demonstrates high mode purity and the presence of TE02 mode confirmed by the field pattern measurement. The mode exciter features high mode purity, broad bandwidth, and is easy to be fabricated, which can be applied to cold-test experiments of gyro-TWT components and the high power transmission line devices.

Planning for Future Solar Farm Development in North Carolina: A Geographic Food Energy-Water Approach

North Carolina (NC) is a large producer of utility-scale solar power and most of the photovoltaics are located on former agricultural lands (solar farms). In 2017 4% of NC power was generated by solar, but plans are in place for higher percentages, which could have consequences for food production and water quality. Geospatial data sets were used to characterize NC watersheds by solar farm development potential. Twenty-seven watersheds were identified as good candidates due to abundance of agricultural lands, presence of high-power transmission lines, and existence of agriculturally impaired waterbodies. These watersheds were somewhat distributed throughout the state, but especially focused in Union County, and 33% contain at least one solar farm. An energy generation model found that for the 27 targeted watersheds, only 2.6% of agricultural land would need to be converted to increase solar's energy portfolio to 5%; and 21.7% would need to be converted to increase it to 12.5%.

A 90° Oversized Broadband TE01-to-TM11 Mode Converter for High-Power Transmission Line

This article proposes a novel method to design a 90° oversized TE01-to-TM11 mode converter for high-power transmission line. In order to obtain a full power conversion at 90° bend angle rather than an acute angle, the mode coupling process inside the oversized circular waveguide bend is analyzed, and a phase rematching method is deduced. Based on the analysis results, a phase rematching structure, consisting of two identical circular-to-elliptical transitions and a uniform circular waveguide which can transform the phase difference from $-\pi $ /2 into $\pi $ /2, is introduced. Two mode converters with the input/output radius of 14 mm are designed at the center frequency of 34 GHz to validate the proposed method. The results show that the mode converter with a limited height has a bandwidth of 4.6 GHz, while the mode converter with a limited width has 4.3 GHz with conversion efficiency over 95%. The mode converter with a limited height is manufactured and measured, and the high-purity outputs are validated by the obtained radiation field patterns at the output port of the mode converter from 32 to 36 GHz. The proposed mode converter provides a new approach for developing a compact, high-efficiency, and broadband high-power millimeter-wave transmission line.

Investigating tension in overhead high voltage power transmission line using finite element method

Transmission line failure is a serious problem in developing countries. The major cause of high voltage overhead transmission line failure in power system is prolonged excessive current. The determination of line segments where high tension is generated due to prolonged excessive current under the different arrangements of line spacing and current carrying conditions can lead us to analyze high tension zones for efficient design of transmission lines. In this context, the mechanical tension on an overhead high voltage electrical power transmission line resulting from excessive or normal currents was computed using Finite Element Method. Multiple segments of a long transmission line with symmetrical and unsymmetrical spacing under accidental and normal line current are examined. Therein, the line segments with high tension are determined. Maximum integrated tension is found in middle segments of both symmetrical and unsymmetrical spaced transmission line. While, maximum per unit tension is found in initial and bottom segments. However, variation in magnitude is found for symmetrical and unsymmetrical spacing. The present study may provide technical guidance to the transmission line design engineers and technicians regarding the risk and solutions related to electrical power transmission line systems.