摘要:

Presents a report of a committee appointed by the Council of the British Electrical and Allied Manufacturers' Association, the Radio Industry Council and the Council of the Institution of Electrical Engineers.The numerical and technical importance of the group classified aselectrical techniciansjustifies attention being drawn to the problem of their training.The principal method of providing for the education and training of electrical technicians should be a four- or five-year apprenticeship or training, according to the standard of entry, with concurrent education in a technical college. The practical aspect of this training is of vital importance.The technical education of a technician should reach a level at least comparable with that of an Ordinary National Certificate. Small but significant modifications in the curriculum for this certificate are desirable in some cases.For a relatively small group the usual Ordinary National Certificate followed by a Higher National Certificate is appropriate.For the majority the modified Ordinary National Certificate course should be followed by a course in specialized technology, for which some existing and some proposed courses are suitable.Attention is drawn to alternative forms of “works-based” sandwich schemes and to the advantage to be derived from cooperation between firms.The practical training needed differs from one group to another, and no uniform scheme is suggested. The principles to be applied are stated.A technician apprentice should have obtained a good general education, particularly in the subjects of Mathematics, Science and English.Provision should be made for the transfer to technician training of craft apprentices and others who show suitable aptitude.Subject to satisfactory progress, technician apprentices and trainees should be given part-time day release to attend classes.

DOI:10.1049/pi-1.1951.0012

出版商:IEE    

年代:1951

数据来源: IET

摘要:

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 10−15cm3of 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.

DOI:10.1049/pi-1.1951.0019

出版商:IEE    

年代:1951

数据来源: IET