High Power Transmission Lines Research Articles

Development of high-power heating for large helical device

Abstract Three high-power heating mechanisms, i.e. electron cyclotron resonance heating, ion cyclotron resonance heating and neutral beam injection heating will be available to achieve operation of the Large Helical Device in the (i) high nτT mode, (ii) high T i mode and (iii) high β mode. The requirements for each heating method are (i) 10 MW of ECH at a frequency of 84 GHz with a pulse length of 10 s, (ii) 3 MW of ICRF heating in the frequency range 25–100 MHz in CW operation and (iii) 20 MW of NBI at a hydrogen injection energy of 125 keV and 10 s operation. The components of each heating mechanism which need development individually exist, i.e. (i) a high-power gyrotron with an output power of 1 MW in CW operation and a high-efficiency transmission line for ECH, (ii) a high-power co-axial transmission line with cooling and an automatic matching circuit for ICRF heating and (iii) a large negative ion source and some components of the beam line for NBI. The heating scenario and the present status of the development are described for each heating system.

Exposure to power-frequency electromagnetic fields in Denmark.

The purpose of the study was to assess exposure to power-frequency electromagnetic fields in various groups with normal or high exposure in occupational and residential environments. Exposure to power-frequency (50 Hz) electric and magnetic fields was measured for 301 volunteers (396 measurements) in periods of 24 h in both occupational and residential environments. The study included electrical utility workers (generation, transmission, distribution, substation), office and industrial workers, and people living near high-power transmission lines. Electric and magnetic fields were measured with personal dosemeters, and the mean values were calculated for work and nonwork periods. The work-period magnetic field exposure, as the geometric mean of the distribution of the work-period means, for a group of selected industrial workers with high exposure was 6 [geometric standard deviation (GSD) 4.6] muT. The exposure level was 0.10 (GSD 2.4) muT for "normal" industrial workers and 0.09 (GSD 1.8) muT for office workers. For electrical utility workers the corresponding values were 0.72 (GSD 2.5) muT for substation workers, 0.52 (GSD 4.2) muT for generation workers, 0.36 (GSD 3.5) muT for transmission workers, and 0.15 (GSD 2.9) muT for distribution workers. The magnetic field exposure in normal residences was 0.04 (GSD 2.1) muT, and in residences near high-power lines it was 0.29 (GSD 2.8)muT. Corresponding results on exposure to electric fields are given in the study. All of the measurements of exposure to electric and magnetic fields were below the values normally used as guidelines.

Risk of childhood leukemia in areas passed by high power lines.

There has been an emerging concern about possible health risks posed by exposure to extremely low frequency electromagnetic fields (EMF). The incidence of childhood leukemia near high-power transmission lines has only rarely been investigated. A total of 67 cases of childhood leukemia (aged 0-14 years) were reported to the Cancer Registration Center in Taiwan between 1979 and 1988 from the five districts in the Taipei Metropolitan Area, where at least one elementary school campus is passed over by a high power transmission line (69-345 KV). The standardized incidence ratio (SIR) of childhood leukemia in the five districts was found to be significantly elevated (SIR = 1.49, 95% confidence interval: 1.16-1.91). Younger children seemed more susceptible to EMF exposure as indicated by the fact that children aged 0-4 years in two of the five districts showed significantly elevated SIRs compared to older ones. The unusually high SIRs for children of age 5-9 and 10-14 years in one of these districts (SIR = 4.38 and 3.68 respectively) deserves further investigation.

AC energy dissipation in high-Tc superconductors

Abstract The AC energy dissipation of high- T c superconducting wires is an important factor which will determine the feasibility of high-power transmission lines using these materials. To obtain a better understanding of AC power loss mechanisms and to determine if their level is acceptable for this application, the losses of Y- and Bi-based samples, prepared by different processes, were measured at 77 K when carrying an alternating current or subjected to a time-varying magnetic field. Hysteresis was found to be the dominant mechanism and the critical state model well describes the experimental results of the weak-link-free samples. Melt-texturing processes greatly reduce the granularity behavior and the AC losses.

地中電力ケーブルの導体温度監視方法の検討

To reinforce the reliability for stable power supply, several maintenance and monitoring systems for the underground power transmission lines have been already applied in main ultra high voltage lines. As one of the monitoring systems, the measuring of exact conductor temperature in loading cables is necessary to smoothly operate the system. Though it is very difficult to directly measure the conductor temperature in the loading cable, conductor temperature is estimated by measuring heat flows radiated from cable surface, cable surface temperatures and load current. In Japan, 275kV aluminium sheathed oil filled (OFAZV) cables are mainly used as the main ultra high voltage underground power transmission lines, while 275kV aluminium sheathed XLPE (CAZV) cable and wire shielded XLPE (WS/CV) cable are recently adopted due to maintenancefree and non-inflammability. But, it is very difficult to estimate the conductor temperature in case that the eddy current losses in cable sheath are relatively large or the heat flows radiated from cable are not uniform such as the trefoil configuration of the aluminium sheathed cables. Therefore, two methods to estimate the conductor temperature in loading cables in arbitrary configurations are proposed, namely by measuring the cable surface temperature and the heat flows radiated from cable, and by measuring the cable surface temperatures and cable load current. The applicability of those methods is verified by using 275kV 1×2, 000mm2 CAZV and 154kV 1×2, 000mm2 WS/CV cables. One of those methods was experimentally applied in acutual underground cable lines, 275kV OFAZV cable for summer in 1989.

A New Generalized Approach to Fault Analysis of High Phase Order Transmission Systems

ABSTRACT High phase-order power transmission lines are being considered by power system engineers as one of the alternatives for augmenting the power transfer capability of existing power corridors. For the practical realisation of such high phase-order transmission lines, fault analysis constitutes one of the important planning studies. In this work, a new, generalized and comprehensive approach is presented to carry out the fault analysis of power transmission systems of any phase-order and under any type of transposition. The procedure is applicable to both earth faults and phase faults and all the desired results can be easily obtained by means of the computer programme specially developed for this purpose. Its flexibility has been demonstrated by application to a sample power system. Also, the discrepancies In the fault analysis procedure of a six phase transmission system reported In an earlier publication have been clearly brought out.

Photoacoustic Spectroscopy of a Chemically Modified Polymer: Plasma Oxidized Polystyrene(Divinylbenzene)

Surface modified polymers are found in a variety of industrial applications ranging from highpower transmission line insulators to chromatographic packaging materials. Infrared spectroscopy has routinely been used to characterize the surface of these materials but often requires sample preparation which may alter the form of the polymer. By using a photoacoustic detector, the infrared spectra of surface modified polymers can be obtained. The polymeric material examined in this study, polystyrene(divinylbenzene), is routinely used as a chromatographic packing material for high performance liquid chromatography. The surface of the polymer was modified to produce surface functionalities more amenable to bonding with a liquid phase than the native copolymer. This paper describes the use of photoacoustic infrared spectroscopy to determine the molecular structure of this modified polymer surface.

The RF Power Plant of the SPS

This paper describes briefly the main components of a RF power system with the exception of the accelerating cavity. A diagram of a 200 MHz accelerating system is shown. The power for the accelerating cavities is provided by a 500 kW amplifier utilizing 2, 4, 8 and 16 tetrodes or one 500 kW klystron. The terminating load is a 6 m long 6 1/8'' stainless steel coaxial line. High power transmission lines with coaxial and waveguide components are discussed.

Use of Optical Cables in Power Transmission Lines

The design problems of an optical fiber cable suitable for installation in high power transmission lines are analyzed. Installation problems and repeater constraints are discussed and an experimental link to be installed in a 400 KV power line in México, as well as cable to be used are described.

Electric and Magnetic Field Coupling from High Voltage AC Power Transmission Lines -- Classification of Short-Term Effects on People

Issues are discussed that are of potential interest concerning people's short-term reactions to ac transmission-line electric and magnetic field coupling effects. Reactions to electrical stimulation are organized into four categories: direct contact currents, spark discharges, direct effects of electric fields, and direct effects of magnetic fields. Within these categories, issues of potential interest concerning transmission-line effects are identified. The state of knowledge and priorities for each issue are assessed. A summary of the state of knowledge concerning electrical stimulation is presented, including data on spark discharges that are published here for the first time. Issues are identified where further research is needed.