摘要:

The features of large networks which are important in the design of selective protective systems are discussed.The characteristics of distance protective relays are considered, and the causes which lead to inaccuracy in their operation are enumerated. It is shown that nearly all these causes are due to the network and not to the relays. The conditions governing the minimum safe clearance times and minimum length of line that can be protected are discussed.An analysis is given of the magnitude and distribution, between earth and the conductors, of earth fault currents on systems with multiple earthing of the neutral point, and the sources of error resulting from this distribution and means of compensating for this error are given.Protective systems depending on direction of fault current are discussed and the “duplex” system is described in detail. It is shown in what way the conditions in a network during a fault may tend to occasion incorrect operation of relays of this type, and how such tendencies may be overcome in the design of the protective gear.The difficulties in the design of protective systems introduced by the distortion of the vector diagram during a fault are explained, and it is suggested that these difficulties may be overcome if the distortion itself is used for relay operation, as may be done by employing negative and zero phase-sequence components.

DOI:10.1049/jiee-1.1932.0148

出版商:IEE    

年代:1932

数据来源: IET

摘要:

The principal cause of inconsistency in the short-circuit performance of oil circuit-breakers is considered to be the erratic movement of the oil. Quick-break circuit-breakers are advantageous for the higher voltages, and still further improved performance and consistency is obtained by the use of suitably-designed contact shrouds. Reference is made to published tests on some of the recent designs. The principal features of design affecting arc rupture are briefly reviewed and are followed by notes on the causes and effects of the magnitude and the rate of rise of recovery voltage.The importance of short-circuit testing is emphasized, and a plea is made for facilities for testing on site. A description of short-circuit testing arrangements is given, including a detailed description of the oscillograph equipment; also general notes on the calculation of 3-phase kVA. Reports are included of recent short-circuit tests carried out on oil circuit-breakers fitted with a new type of shrouded contact.

DOI:10.1049/jiee-1.1932.0149

出版商:IEE    

年代:1932

数据来源: IET

摘要:

The object of the paper is to indicate that the changing-over of existing low-tension networks from direct current to alternating current can be carried out in a satisfactory and advantageous manner from an engineering as well as from an economic standpoint.The problems arising in dealing with small townships, and with suburban and residential areas, are quite different from those which arise in industrial and city areas. The paper has consequently been divided into three parts, Part 1 dealing with suburban and residential areas, Part 2 with industrial and city areas, and Part 3 with the general aspect of changing over.As a result of investigations, the authors are of the opinion that, irrespective of loading conditions, residential and suburban areas should be changed over to a.c. supply at the earliest possible opportunity, but that in industrial and city areas the rate of change-over should depend upon the growth of the d.c. load and the condition of the d.c. converting plant. In all areas, however, the “standard” 3-phase 4-wire a.c. system should ultimately be adopted.

DOI:10.1049/jiee-1.1932.0152

出版商:IEE    

年代:1932

数据来源: IET

摘要:

In the first part of the paper the principles underlying modern communication engineering are discussed. The second part of the paper deals with some characteristic examples of the multiple utilization of transmission systems, such as 2-band systems and simultaneous telephony and telegraphy using short waves.

DOI:10.1049/jiee-1.1932.0157

出版商:IEE    

年代:1932

数据来源: IET

摘要:

A systematic investigation with the aid of an oscillograph into the behaviour of brushes running on a short-circuited commutator is described. Each brush was divided into two or more parts insulated from each other so that the distribution of current across the face of the brush could be examined. The difficult problem of reversible running received special consideration. The commutator contained a slightly high bar and two flats in order to determine the relative merits of different brush and brush-holder arrangements on an imperfect commutator. A distinction is drawn between the effect of “sudden” irregularities as exhibited by high bars, and of a “gradual” irregulalrity such as eccentricity of the commutator. The advantages of using a pressure finger of high inertia and the importance of low inertia in the brush itself are demonstrated. Finally, suggestions are made concerning the lines along which further investigation should proceed.

DOI:10.1049/jiee-1.1932.0161

出版商:IEE    

年代:1932

数据来源: IET

摘要:

The paper describes briefly the principles of the resonance method of wave-form analysis. A short account is included of the other methods of analysis that are available, and a historicalrésuméof the resonance method is give. The desirability of basing the analysis on a measurement of the voltage across the inductance coil in the resonance circuit is demonstrated from theoretical and practical considerations. The most suitable form of analyser is described and the advantages of the thermionic voltmeter for this prupose are indicated. A selection of the results obtained are included to to illustrate the applications of the method.

DOI:10.1049/jiee-1.1932.0162

出版商:IEE    

年代:1932

数据来源: IET

摘要:

Formulæ for the capacitance of a guard-ring sphere-gap are derived by the method due to G. R. Dean (Physical Review1913, vol. 1, p. 316) in which a solution of Laplace's equation is employed, and also by the well-known method of point charges (A. RUSSELL, “ Alternating Currents,” vol. 1, p. 236). Expressions suitable for computation are given for the practical case of equal spheres. A few numerical examples are also given, together with the measured values of the capacitance of a 50-cm guard-ring sphere-gap

DOI:10.1049/jiee-1.1932.0163

出版商:IEE    

年代:1932

数据来源: IET