Journal of the Institution of Electrical Engineers
About: Journal of the Institution of Electrical Engineers is an academic journal. The journal publishes majorly in the area(s): Transformer & Induction motor. It has an ISSN identifier of 0099-2887. Over the lifetime, 1728 publication(s) have been published receiving 9687 citation(s).
Papers published on a yearly basis
TL;DR: In this paper, a model of inhomogeneous material containing spheroidal particles is investigated analytically and it is concluded that a minute amount of conducting impurity in the form of fine needles could produce a serious loss at low frequencies.
Abstract: It is pointed out that, although dielectric losses in certain materials are frequently attributed to the presence of particles of conducting impurity, any discussion as to the type and magnitude of loss produced by a given quantity and disposition of impurity is often extremely vague or entirely lacking. A description is given of some experiments with a suspension of water droplets in wax, the results of which did not agree with the predictions of Wagner's theory except when the suspension was kept at a temperature near to the melting point of the wax. The behaviour of a model inhomogeneous material containing spheroidal particles is investigated analytically and it is concluded that a minute amount of conducting impurity in the form of fine needles could produce a serious loss at low frequencies, although the effect of the same quantity of impurity in spherical form would be negligible.
TL;DR: In this paper, a critical examination is made of the somewhat loose and incomplete statement that a polar diagram is the Fourier transform of an aperture distribution, and it is shown that if the aperture distribution is of such a nature that the concept of polar diagrams is applicable at sufficiently great distances, then the polar diagrams are equal to the angular spectrum.
Abstract: A critical examination is made of the somewhat loose and incomplete statement that a polar diagram is the Fourier transform of an aperture distribution. By aperture distribution it is necessary to understand, in the two-dimensional case, distribution across the aperture of the component along the aperture plane of the electromagnetic field in the plane of propagation. Furthermore, the concept of the polar diagram has to be replaced by that of an angular spectrum, except in the common case when the aperture may be considered more or less limited in width, and the field is being evaluated at a point whose distance from the aperture is large compared with the width of the aperture (and the wavelength). For example, it is convenient for some purposes to regard the problem of diffraction of a plane wave by a semi-infinite plane screen, with a straight edge, as a problem about an aperture distribution in the plane of the screen. This is a case for which the concept of a polar diagram is not in general applicable, and has to be replaced by that of an angular spectrum. The field at all points in front of a plane aperture of any distribution may be regarded as arising from an aggregate of plane waves travelling in various directions. The amplitude and phase of the waves, as a function of their direction of travel, constitutes an angular spectrum, and this angular spectrum, appropriately expressed, is, without approximation, the Fourier transform of the aperture distribution. If the aperture distribution is of such a nature that the concept of the polar diagram is applicable at sufficiently great distances, then the polar diagram is equal to the angular spectrum. But the angular spectrum is a concept that is always applicable, whereas the polar diagram is one that is liable to be invalid (for example, in the Sommerfeld theory of propagation over a plane, imperfectly reflecting earth).
TL;DR: In this article, the degradation of polythene and other dielectrics, when exposed to internal discharges, has been examined under controlled conditions, and the discharge-inception voltage and the magnitude and energy of individual discharges have been determined, by electrophotography.
Abstract: The deterioration of polythene and other dielectrics, when exposed to internal discharges, has been examined under controlled conditions. The discharge-inception voltage and the magnitude and energy of individual discharges have been determined, and the location and number of discharges in voids of different dimensions have been studied, by electrophotography. The discharge sequence is explained by the difference in the distribution of the residual charges on the positive and negative surfaces of a void after a discharge. Accelerated deterioration tests using a frequency of 150 kc/s show that, initially, discharges cause slow erosion at the surfaces of the void and the formation of a transparent film of resin which fluoresces under ultra-violet irradiation. About 10 -15 cm 3 of polythene is eroded by each discharge, probably as a result of thermal degradation. The rate of deterioration increases rapidly with increasing voltage; at twice the discharge-inception voltage, the discharges concentrate and form several deep uncarbonized pits near the periphery of the void. When the pits attain a critical length, the mechanism of deterioration is believed to change; narrow semi-carbonized channels are found and, generally, breakdown follows immediately. Deterioration is greater when the void is adjacent to an electrode than it is when the void is enclosed in polythene. Tests show that, under equivalent conditions, polytetrafluorethylene and perspex are less resistant to discharges than is polythene.
TL;DR: The meeting of the Advisory Technical Committees of the International Electrotechnical Commission (ITC) was held in Brussels from March 27th to April 1st, 1989 as mentioned in this paper.
Abstract: Meetings of the Advisory Technical Committees of the International Electrotechnical Commission were held in Brussels March 27th to April 1st. The meetings were attended by delegates from eight national committees — Belgium, France, Great Britain, Holland, Italy, Spain, Switzerland, and the United States. There were about 40 delegates in all.
TL;DR: In this paper, the problem of ground-wave propagation over an inhomogeneous smooth earth is discussed in terms of the known solution for a homogeneous earth, and the fundamental results of the theory for homogeneous Earth are described in a form directly useful to the argument.
Abstract: The problem of ground-wave propagation over an inhomogeneous smooth earth is discussed in terms of the known solution for a homogeneous earth. The inhomogeneity refers only to changes in the earth constants from place to place, and the problem is idealized by assuming a wave radiated from a vertical dipole over a series of homogeneous annular sections. After a statement of some of the conditions the solution would be expected to obey, including the essential one of reciprocity, some fundamental results of the theory for a homogeneous earth are described in a form directly useful to the argument. The solution is first given for the short-wave limit, where it is complete except in the neighbourhood of a boundary. By an approximate consideration of the energy flow at different heights above the ground, the solution is extended to the case of intermediate wavelengths where the first and last boundaries are in the diffraction region of the transmitting and receiving points respectively. It is then shown that a well-known empirical method yields the same solution when it is made reciprocal by taking the geometric mean of the value it gives and the value that would be obtained with the transmitter and receiver interchanged. This method is formally used to obtain a tentative solution for the effect of the disturbance function in the neighbourhood of a boundary. It leads to the striking suggestion that on passing from a section of one value of conductivity to another of a higher one, there is a recovery in field-strength before the attenuation of the wave becomes characteristic of the new section. On crossing the boundary in the other direction, there is a correspondingly increased drop in field strength before the attenuation takes its new characteristic type. Owing to the lack of sufficiently controlled conditions, most of the existing experimental results are inconclusive with regard to these features at a boundary, but some evidence is given in support of them. Stress is laid on the need for further experiments specifically designed to study the field near a land-sea boundary. The paper deals briefly with the practical application of the method, and gives a specimen field-strength/distance curve for a route consisting of several land and sea sections. It concludes by pointing out that further research is needed, especially with regard to the phase relationships, as the argument has dealt only with field-strength values.
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