UHV Transmission Research Articles

A study on a coreless superconducting transformer

A conceptual design for a 1000-MVA-class coreless superconducting autotransformer (CLSCAT) has been developed. For a preliminary experimental study, a small 2.5-kVA CLSCAT has been manufactured and tested. The test result shows that though the exciting current of the CLSCAT is very large, its voltage drop is relatively small compared with the cored transformer. The dielectric strength of liquid helium has been tested using an insulation model. From the insulation test, the availability of the fundamental insulation structure composed of the lamination of small liquid helium gaps separated by solid barriers has been confirmed. From the conceptual design of a 1000-MVA-class CLSCAT, it becomes clear that the CLSCAT has an additional reactive power of about one-third of its rated capacity. This large reactive power can be utilized for the compensation of the capacitive charging current of a cable line or a UHV transmission line. The operating loss, was calculated to be about two-thirds of the conventional transformer. However, this figure is reduced to one-half if the additional reactive power of the CLSCAT is considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Insulation recovery characteristics after fault arc interruption on UHV (1000 kV class) transmission lines

The insulation recovery time after arc interruption must be known to select the adequate reclosing dead time of rapid auto-reclosing on transmission lines. In order to study insulation recovery characteristics after arc interruption on UHV (1000 kV class) transmission lines, many tests were carried out using the high power test facilities of CRIEPI. In this paper the authors describe the experimental results of these tests of insulation recovery characteristics after arc interruption of UHV transmission lines, and some factors influencing these characteristics. >

A microprocessor-based quadrilateral distance relay for [formula omitted] transmission line protection

This paper presents an Intel 8086 microprocessor-based quadrilateral distance relay suitable for the protection of EHV UHV transmission lines. The digital filtering algorithm used for extracting the fundamental frequency components from the complex post-fault relaying signals is based on rationalized Haar transform (RHT). The real and reactive components (R and X) of the apparent impedance of the line as seen by the relay are computed by using the real and imaginary components of the fundamental frequency voltage and current phasors. Using the computed values of R and X, the microprocessor examines whether the fault point lies within the quadrilateral relay's protective zone or not. If the fault point lies in the protective zone of the relay, the microprocessor issues a trip signal to the circuit breaker. The proposed distance relay is reliable, flexible, accurate and fast.

Registry and UHV transmission electron diffraction of surfaces

A model using a distorted wave analysis coupled with considerations of registry and channeling is developed for understanding high-energy electron diffraction from surfaces in a plan-view geometry. We show that this model explains strong effects due to inelastic scattering, particularly for the 1×1 surface as a function of beam orientation with respect to the underlying bulk substrate and with respect to the effect of registry on intensities. Numerical simulations using the multislice algorithm are correlated with the model, and show additional complications due to a top-bottom effect and coupling.

A new Kalman filter approach to digital relaying

A novel Kalman filter approach to digital relaying is presented, in which the traditional application of simple, low-cost analog prefilters is assumed. The sampling rate is not directly coupled to the filter bandwidth; while this one was specified as low (150 Hz at maximum), the sampling period was determined by time resolution and processing cost requirements (1 kHz). To cope with the signal distortion resulting from the prefilters' own transients, a novel observation model is developed for the Kalman filter, with very little extra processing. The coloring effect on the observation noise by prefiltering is modeled in the Kalman filter state space, assuming white input noise, but the simulation tests with a modal-based impedance estimator show that little improvement is achieved with that. Instead, the addition of a colored time-decaying sinusoid to observation white noise in the state space supports improved performances, especially for very noisy faults in long UHV transmission lines with weak sending buses. Time decisions between 1/3 and 1/2 cycle were achieved for faults at the ending bus and at mid-line, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multistory transmission tower model for lightning surge analysis

A multistory transmission tower model to be used in multiconductor analysis by EMTP (Electromagnetic Transients Program) is proposed. The circuit parameters of the model are determined based on the measurement of voltages across the insulator strings on an actual 500 kV transmission tower. The multiconductor lightning surge analysis considered enables one to predict the waveform of each insulator voltage, which is useful in determining the phase and the instant of a back flashover. The new tower model is recommended in Japan to be used in the new multiconductor analysis of EHV and UHV class double circuit transmission lines. The new tower model and conventional tower models are compared in the analysis of minimum back flashover lightning currents at a UHV transmission line. The new model gives about 20% smaller current. >

The direct observation of the Ge(001) dimer structure by high resolution UHV transmission electron microscopy

The dimer structure of the (001) surfaces of the germanium particles and dynamical rearrangement are observed in real space and in real-time by high resolution UHV electron microscopy. From the computer simulation of the electron microscope images it is found that the dimers are asymmetric and change their dipole directions.

The direct observation of the Ge(001) dimer structure by high resolution UHV transmission electron microscopy

The direct observation of the Ge(001) dimer structure by high resolution UHV transmission electron microscopy

The Etching of Silicon by Oxygen Observed by in situ Tem

ABSTRACTWe describe observations made in situ in a modified UHV transmission electron microscope of the process of etching of the Si (111) surface by oxygen. Etching occurs by the motion of individual bilayer steps across the surface and by analysing the step motion we discuss the etching mechanism in the context of macroscopic parameters.

High Energy Transmission Electron Diffraction From Surface Monolayers During Silicon Oxidation

ABSTRACTWe have examined the behaviour of the clean Si (111) 7x7 reconstructed surface during exposure to oxygen over a range of temperature and pressure in a UHV transmission electron microscope (TEM). We present preliminary results of our study, discussing both the etching of the silicon surface by oxygen at elevated temperatures and lower oxygen pressures, and its roughening and oxidation at higher oxygen pressures. We achieve great sensitivity to the structure of the surface monolayers by analysing the diffraction of high energy electrons by these surface layers and can resolve the movement of individual monatomic surface steps. Our most dramatic result to date is a demonstation that surface steps do not move during the growth of native oxide.

In-Situ Studies of Silicon Oxidation

Using a UHV transmission electron microscope we have examined the initial stages of Si oxidation. Using the surface-sensitive forbidden 1/3 reflection on Si (111) we have imaged surface steps at various stages of oxidation, including buried Si/SiO 2 interface formation.

Practical design of AC 1000 kV insulator assemblies

The design features of the arc horn applied to the insulator assemblies for AC UHV transmission lines are described. These features have been developed on the basis of detailed studies conducted on the corona characteristics and insulating performance. Since the characteristics of the arc horn for the UHV-class insulator assemblies can not be predicted by the extrapolation of the design practice for those of a 500 kV class, the design features have been validated by full-scale tests. A practical design of the arc horn applicable to AC 1000 kV transmission-line insulator assemblies were obtained by making the most use of such effects as the corona shield effect of the conductor and the effect of the electrode configuration on the switching impulse flashover voltage characteristics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of Parameters on The Phase-to-Phase Flashover Characteristics of UHV Transmission Lines

Effects of Parameters on The Phase-to-Phase Flashover Characteristics of UHV Transmission Lines

Effects of Parameters on the Phase-to-Phase Flashover Characteristics of UHV Transmission Lines

Phase-to-phase flashover characteristics needed for insulation design of UHV transmission lines, such as between 8-conductor to 8-conductors configuration and between the jumper line to the lower shield ring were investigated. The results include: (1) Effect of wave front duration of applied voltage. (2) Effect of positive-to-negative voltage ratio. (αm) (3) Effect of time difference between wave peaks of positive and negative voltages. (4) Gap distance characteristics of flashover voltage.

Computation of Electric Fields Using Ground Grid Performance Equations

This paper presents a methodology for calculating electric fields in EHV transmission lines and substations using ground grid performance equations. The computed values proposed by our method compare very favorably with the experimental data published in the literature. The effectiveness of the shielding wires in the UHV transmission lines entering into a substation is investigated. Phase sequence of superposed busbars is also considered. The presence of urban residential buildings near EHV transmission lines is analyzed.

ON LINE MICROPROCESSOR BASED RELAYING SCHEME FOR EHV/UHV TRANSMISSION LINE: AN EXISTING 400 kV LINE

ABSTRACT One of the most challenging Job have been towards the development of relaying scheme for the protection of transmission line,because of its long length and its consequent, exposure to atmospheric hazards; therefore, BHV and UHV transmission systems need a reliable, fast, efficient and low cost protection scheme. Protection schemes using microprocessor is ahead in this direction as it is capable of realizing any type of complex threshold characteristics with changes in the software along and with minimal changes in the hardware. It is also capable of doing self-checks. The present paper is a step to this direction where microprocessor based protection scheme for on line protection of EHV/UHV transmission line using the fundamental components is designed, fabricated and tested in the lab. The proposed scheme is also Immune to transients.

Computation of Electric Fields Using Ground Grid Performance Equations

This paper presents a methodology for calculating electric fields in EHV transmission lines and substations using ground grid performance equations. The computed values proposed by our method compare very favorably with the experimental data published in the literature. The effectiveness of the shielding wires in the UHV transmission lines entering into a substation is investigated. Phase sequence of superposed busbars is also considered. The presence of urban residential buildings near EHV transmission lines is analyzed.

ＵＨＶ送電線の対コロナ雑音設計

ＵＨＶ送電線の対コロナ雑音設計

Jicable 84 International Conference on Polymer-Insulated Power Cables

JICABLE 84, which was the first international conference on polymer-insulated power cables, took place in Versailles from 5 to 10 March 1984. This paper summarizes the works that were presented during the conference. The mains topics discussed are: - materials and components for polymer insulated power cables; - cables and accessories for LV and MV distribution power systems and HV and UHV transmission power systems; - submarine cables; - cables with improved fire behavior. Furthermore, this paper gives a summary of the work undertaken by a workshop (called Workshop HT 84) organized in connection with JICABLE on the behavior of polymer insulated HV cables at high temperature. From the discussions, it follows that the use of these cables at high temperature must not be envisaged without certain technical and economic reservations.

A Multi-Microprocessor Based Travelling Wave Relay - Theory and Realization

A new travelling wave digital protection scheme to be used as an ultra high speed (UHS) EHV/ UHV transmission line relay is presented in this paper. Some of the potential problems and limitations associated with other travelling wave schemes are avoided. Verification of the relay operating principles is presented through digital computer numerical simulation using an electromagnetic transients program (EMTP) in conjunction with simulation of the proposed algorithm. Parallel digital processing is incorporated through multi-microprocessor implementation. Hardware and software of a multiprocessor prototype are managed in a way to fit the algorithm requirements in as simple a construction as possible. The resulting scheme achieves significantly improved security and dependability, in addition to the main features: fault classification and UHS phase selection in selective-pole schemes with minimum communication between the protected ends.