Line Entrance Research Articles

1100 kV substation ‐ basic design/specifications of GIS for UHV AC and its verification test and site

AbstractIn Japan, to satisfy the steadily increasing demand for electricity in urban areas, 1100 kV substation equipment have been developed, and a part of the 1100 kV transmission lines were constructed. 1100 kV substations would be located in the mountainous areas, so they must be made as compact as possible to meet installation space constraints and to harmonize with the natural environment. Thus, 1100 kV substations adopt Gas Insulated Switchgear (GIS) as the main circuit from transmission line entrance to transformer bushings. Because the substation is one of the most important items in a 1100 kV system, the equipment in 1100 kV substations requires to be of extremely high reliability. Additionally, various technologies that have not been used in 500 kV and lower systems are applied. To establish carefully the 1100 kV equipment technologies, TEPCO constructed a UHV Equipment Test Station (in the 500 kV Shin‐Haruna substation), which has the minimum component of a 1100 kV substation‐3 single‐phase transformers (3000 MVA bank) and 1 bay of GIS (8000 A). Connecting these facilities to the actual grid in 1996, a field verification test has been carried out. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

EUV and X-Ray Solar Flares Observed on-board the “Coronas-F” Satellite

The CORONAS-F satellite has been launched on 31 July 2001 (Oraevsky et al. 2002). To conduct measurements of the intensity of solar radiation in the EUV spectral region near the hydrogen line entrance window.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Buoyantly-driven two-phase countercurrent flow in liquid discharge from a vessel with an unvented gas space

This paper details experiments and analyses regarding the phenomenon of liquid discharge into a gaseous atmosphere from the bottom of a vessel with an unvented, upper gas space. The primary goal is the development of a simple model that predicts the rate of liquid discharge under the prevailing unvented condition. A literature survey of previous work on this phenomenon yielded only simple experiments and analyses that were limited in scope. Experiments were subsequently undertaken with an air-water system, using a larger volume and a wide range of drain line diameters. In addition to flowrate data, visual information was acquired regarding the physical mechanism possibly governing the prevalent flow regimes. The governing physical mechanism is identified as the stability of a gas-liquid interface, perturbed by buoyancy, at the drain line entrance. G.I. Taylor's fundamental analysis of interfacial stability lead to the determination of criteria for flow regime transition among the three prevalent flow regimes, corresponding to so-called small, medium, and large diameters. Also, analysis of the growth of interfacial instabilities lead to the application of flooding models for drainage rates within each regime. The models for moderate and large diameters were then compared against data, which confirmed their success in predicting discharge rates under the unvented condition. The motivation for this effort, besides the basic scientific significance of studying such a fundamental phenomenon, was its numerous applications, one of which is commercial nuclear reactor systems. Specifically, the phenomenon prevails in liquid coolant discharge from a PWR pressurizer, with an unvented steam volume, into a steam atmosphere existing in the adjoining hot coolant leg. Such a phenomenon could occur as part of a transient, or severe accident, scenario, entailing saturated conditions and steam production in the normally subcooled primary heat transport loop. The developed model was implemented in the Modular Accident Analysis Program (MAAP), a computer code designed to predict reactor system behavior in response to postulated off-normal conditions, including severe accident scenarios.

Lightning Surge Analysis in a Multi-Conductor System for Substation Insulation Design

Analysis of back flashover lightning surges coming into a substation is important to understanding of substation insulation co-ordination. These surges are usually analyzed for a single conductor system, but in this paper, they were analyzed with EMTP for a multi-conductor UHV system consisting of two ground wires and six phase conductors. It was clarified that lightning surge voltages on the phase conductor decreased due to negative reflection of the lightning surge at a tower, and the electrical coupling between the ground wire and phase conductor. The multi-conductor system was applied to surge analysis for the line entrance circuit of a gas insulated substation.

Line Entrance Protection of 500 KV Gas Insulated Substations by SF6 Spark Gaps

The use of both station arresters and line entrance arresters provides absolute protection for all operating conditions of gas insulated substations (GIS). However, it represents a costly installation. Hence the adoption of line entrance rod gaps in air can be taken into consideration. But their protection ability is questionable because the slope of the V-t curves for air gaps is much steeper than that for GIS, while SF6 spark gaps with good sparkover characteristics would meet the requirements for the ability to protect the line entrance apparatus of GIS.

Open Breaker Protection of EHV Systems

Although the use of line-entrance lightning arresters provides absolute protection for an open breaker condition, it represents a costly installation. No line entrance protection represents some risk of breaker damage. Line entrance rod gaps offer a compromise between these extremes. This paper discusses the probabilities of failures using these three alternatives and describes a procedure whereby the spacing of the line-entrance gap can be determined. Since this procedure depends on the particular configuration of the gap being used, test data are presented on one particular configuration used on a 345-kV system. Based on these data, recommended gap spacings for 345-and 500-kV systems are developed.

Line Entrance Gaps for Protection of Substation Insulation

Line Entrance Gaps for Protection of Substation Insulation

A Surge-Impedance Analog of a Large Generating Plant Switchyard

Surge-impedance analog studies of lines and stations as illustrated in this paper are applicable to a wide range of powersystem surge performance problems. It is conceivable that a building-block type of analog could be constructed with plugin units designed to represent circuit elements such as a single station bay, a line entrance, or an entire bus section. Regardless of how the analog may be constructed, the method offers a low-cost reasonably simple method to obtain surge performance data on complex circuits that otherwise could only be approximated. As these approximations have, in many past cases, contained what might be termed ignorance factors, the result has been extreme conservatism in the application of overvoltage protective devices. This is evident in the widespread

Development in lightning protection of stations

THE AIEE transformer sub-committee has recently sponsored a paper <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> on the protection of power transformers against lightning surges. The most effective method given combines overhead ground wires, line entrance gaps, and transformer mounted lightning arresters. Such a method does give a high degree of protection, but it is primarily applicable to high voltage, high capacity stations where the overhead ground wire system is justified for both line and station. The conditions noted above are seldom fulfilled on subtransmission systems from 23 kv to 34.5 kv. Effective ground wires and low ground resistances are uneconomical, and the protection provided is usually a more or less modern arrester, not always located and grounded to the best advantage. On the 23-kv subtransmission system of the Duquesne Light Company, the average transmission distance is approximately two miles. This means that most direct strokes will contact the line not more than one mile from some substation. Much of this transmission is now equipped with wood cross arm braces and guy insulators, and at some stations several spans adjacent thereto are carried on unguyed poles.

Development in Lightning Protection of Stations

THE AIEE transformer sub-committee has recently sponsored a paper1 on the protection of power transformers against lightning surges. The most effective method given combines overhead ground wires, line entrance gaps, and transformer mounted lightning arresters. Such a method does give a high degree of protection, but it is primarily applicable to high voltage, high capacity stations where the overhead ground wire system is justified for both line and station. The conditions noted above are seldom fulfilled on subtransmission systems from 23 kv to 34.5 kv. Effective ground wires and low ground resistances are uneconomical, and the protection provided is usually a more or less modern arrester, not always located and grounded to the best advantage. On the 23-kv subtransmission system of the Duquesne Light Company, the average transmission distance is approximately two miles. This means that most direct strokes will contact the line not more than one mile from some substation. Much of this transmission is now equipped with wood cross arm braces and guy insulators, and at some stations several spans adjacent thereto are carried on unguyed poles.

Lightning Studies of Transformers by the Cathode Ray Oscillograph

Study of transformers has been under way for some time to coordinate the strength of transformers and transmission line insulation under lightning conditions. This study has taken two forms: first, the transient dielectric strength of the line end of the winding and second, the distribution of transient voltages and therefore the stress caused by them throughout the winding. Theoretical studies and spark-gap tests of transient voltage distribution in transformer windings have been previously published by the Institute. Since then an extensive study of transient voltage phenomena has been made by the cathode ray oscillograph on power transformers connected to a short transmission line and subjected to artificial lightning waves sent along the line. The effects of the transmission line, concentrated inductance, and transformer entrance bushings on traveling waves were studied, as well as the effect of traveling waves of various service conditions in producing internal oscillations in ordinary transformers. The non-resonating transformer was stutdied under similar conditions. A striking agreement between the oscillographic records and theoretical conclusions previously published was found, sufficient to establish beyond any doubt the following conclusions: 1. Very high voltage oscillations occur throughout the entire winding of even a grounded neutral transformer. 2. Points of the winding near the grounded neutral may rise to 95 per cent of the crest voltage of a very short traveling wave (three microseconds long). 3. Entrance bushings have a negligible effect on the shape of the incoming traveling wave. 4.