摘要:

The first part of this paper deals with lightning as a physical phenomenon. The formation of thunderclouds is associated with convectional instability of the atmosphere, the separation of charge being effected by the resulting upward currents of air. Lightning strokes usually discharge negative electricity into the ground and consist of a preliminary “leader” stroke from cloud to ground followed by a powerful “return” stroke from ground to cloud. A complete flash usually consists of a sequence of such double strokes separated by time-intervals of the order of 10−2sec. The distribution of flashes to earth under a storm centre is influenced by the distribution of space charge above the ground and by discontinuities of conductivity in the ground itself.The second part of the paper deals with the effects of lightning strokes to overhead transmission lines. It is concluded that direct strokes to line conductors are certain to cause flashover: interruption to supply may be minimized either by devices to clear such faults (Petersen coils, expulsion protective gaps), or by overhead earth wires, which will preventanystrokes falling on the line conductors. Strokes to towers and earth wires are unlikely to cause flashover of a line insulated with 9 standard cap-and-pin units, if tower footing resistances are below 10 ohms; footing resistances low enough to prevent flashover with only 3 cap-and-pin units may be impossible to obtain.

DOI:10.1049/jiee-1.1937.0104

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper discusses the performance of noise meters, such as are used for engineering measurements, in terms of the primary standard of “Equivalent Loudness” which has recently been formulated. The unit of equivalent loudness is the British Standard Phon. The technique for the basic determination of the equivalent loudness of a noise is discussed, and the Phon values for a number of specific noises of importance in engineering are given. The fundamentally important equal-loudness relations for pure tones of differing frequency are considered, and the results of some direct determinations in the free field are given. The performance of subjective noise meters is then examined for noises of various types. A meter using two telephone receivers, which offers some advantage over the more usual types, is described. The performance of the objective type of meter is also examined. The measurement of noise associated with irregular sound fields is briefly discussed.

DOI:10.1049/jiee-1.1937.0114

出版商:IEE    

年代:1937

数据来源: IET

摘要:

This paper describes the steps leading up to the present electrification of the Pennsylvania Railroad, the system used, the extent, and the operating results. The 4-track main line is now electrified between New York, Philadelphia, Wilmington, Baltimore, and Washington, as are also the commutation lines around Philadelphia and New York.Since this paper was prepared, work has started on the extension of the electrification to include the connecting lines for both passenger and freight service west to Harrisburg, Pennsylvania. The chief parts of lines in the new electrification are the main line from Paoli, just west of Philadelphia, through Lancaster to Harrisburg; the low-grade freight line from Morrisville, Pennsylvania, near Trenton, New Jersey, via Columbia to Enola Yards, near Harrisburg; the freight line from Columbia following the Susquehanna River to Perryville, Maryland; the freight line from Monmouth Junction to South Amboy, New Jersey, with necessary yards, connecting branches, and equipment.The new work will involve the electrification of 315 miles of line and 773 miles of track. Upon its completion the Pennsylvania Railroad system will have 41 per cent of the total electrically-operated standard railroad track in the entire United States.

DOI:10.1049/jiee-1.1937.0116

出版商:IEE    

年代:1937

数据来源: IET

DOI:10.1049/jiee-1.1937.0117

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper is concerned with the theory and application of a vector diagram for synchronous machines which is expressible in terms of coefficients that are easy to measure if a source of large wattless currents is available.This vector diagram is compared with the diagrams in general use, and some reasons are advanced, in regard to the latter, for the discrepancies between predicted and observed results which may occur when they are applied.The theory of the diagram and the tests necessary for the definition of its coefficients are considered for the cases of a salient-pole and barrel-rotor machine on infinite busbars and on bars of varying voltage, and it is shown that, in general, good agreement is obtained between the predicted and observed results for regulation and load-angle shift.In the Appendix, a brief outline of the mathematical theory is provided.

DOI:10.1049/jiee-1.1937.0120

出版商:IEE    

年代:1937

数据来源: IET