DOI:10.1049/ji-2.1941.0010

出版商:IEE    

年代:1941

数据来源: IET

摘要:

The paper gives an account of an investigation into the magnitude of lightning voltages and currents measured on power transmission lines. The research was undertaken primarily in South Africa, on a 40-kV power line of the Victoria Falls and Transvaal Power Co. Later the work was continued in Nigeria on a 33-kV line of the Nigerian Electricity Supply Corporation's system. The apparatus used in the investigation comprised (a) a high-speed continuously-evacuated cathode-ray oscillograph, (b) a klydonograph, and (c) magnetic links for current measurement. The results obtained are analysed and compared with similar measurements made in other parts of the world.

DOI:10.1049/ji-2.1941.0011

出版商:IEE    

年代:1941

数据来源: IET

摘要:

The nature of internal discharges in actual insulation and also on model circuits exposed to alternating voltages is studied by means of a special oscillographic bridge equipment. A theory of the occurrence of these discharges is developed and is shown to agree with the oscillographic observations and to give correctly the effect of varying different conditions. Examples of the different kinds of phenomena which may occur are given, illustrating the qualitative and, in some instances, quantitative application of the theory. It is shown that, with alternating voltages, discharges, once initiated, can continue at a much lower voltage than that which corresponds to the critical or ignition stress in the dielectric.

DOI:10.1049/ji-2.1941.0012

出版商:IEE    

年代:1941

数据来源: IET

摘要:

This paper describes how the scientific method can be applied to the design of three types of electric heating element—pencil-type radiant elements, plate-type clamp-on elements, and immersion-type elements. In the first case a method of analysis is developed whereby the dimensions of former and wire may be simply determined, and in the latter cases the method of constructing design charts is given together with examples of their use.

DOI:10.1049/ji-2.1941.0013

出版商:IEE    

年代:1941

数据来源: IET

摘要:

This paper describes theoretical and experimental work on the dielectric loss of films of insulating liquids so thin that the motion of ions under an alternating field is limited by the boundaries of the film. Films of this thickness normally occur in porous, impregnated insulation, and lead to a dielectric loss angle which varies greatly with the applied stress.In Section (2) of the paper approximate equations are established for the dielectric loss of such a thin film, as a function of the applied stress. It is also shown that measurements on thin films afford a new method of deducing the ionic concentration, radius and mobility.In Section (3) experimental work is described upon films of an insulating liquid (trichlorbenzene) as thin as 0.03 mm. Such films show a large variation of loss angle with stress, agreeing closely with the predicted variation, except in one or two cases where the nature of the ionized impurities appeared to be abnormal. Values of ionic radius and mobility deduced from the equations of Section (2) check well with values known from electrolytic measurements. It is concluded that experiment confirms the theory put forward, except at very low stresses, where assumptions made in the theory are no longer valid.In Section (4) the equations of Section (2) are applied to an actual impregnated dielectric with non-uniform pore sizes, and it is shown that provided account is taken of the distribution of pore sizes, the theory will account satisfactorily for the variation with stress of the loss angle of condensers impregnated with liquids containing ionized impurities. Values of ionic radius and mobility deduced from these results are also of the right order of magnitude, but are less accurate than those obtained in Section (3), owing to lack of knowledge of the exact distribution of pore sizes.Detailed conclusions are given at the end of the paper.

DOI:10.1049/ji-2.1941.0014

出版商:IEE    

年代:1941

数据来源: IET

摘要:

This report examines data relating to the parameters governing transients of restriking voltage on 132-kV overhead-line systems. From these data, which were obtained partly by short-circuit tests at full voltage and partly by low-voltage measurements, it is concluded that for most calculations relating to transients of restriking voltage in such networks, it is justifiable to use the power-frequency parameters of inductance and capacitance, and to neglect losses.In the network examined, rates of rise of voltage at the clearance of the first phase of a 3-phase fault under normal working conditions ranged from 600 to 4350 volts per microsecond at different points, the former relating to a circuit-breaker fed through a long line, the latter to a circuit-breaker adjacent to the transformer through which it is supplied.It is show in this report that at the start and during clearance of short-circuits, there may exist transient oscillatory currents of a few kilocycles frequency and quite large amplitude. These currents had quite an appreciable effect on the transients of restriking voltage observed in the short-circuit tests discussed: but it is concluded that their effect will be small under normal working conditions, since power-frequency fault currents will then be considerably larger in relation to the oscillatory currents.

DOI:10.1049/ji-2.1941.0015

出版商:IEE    

年代:1941

数据来源: IET