摘要:

Submarine power cables in the United States are frequently made with rubber insulation for voltages up to 35 kV phase-to-phase. The choice of rubber rather than oil-impregnated paper, and the elimination of the lead sheath, is usually governed by physical and chemical conditions rather than cost.The type of rubber insulation preferred is “oil base”, an ozone-resisting compound having good electrical stability when exposed to water, heat and high voltage.The advantages of the longitudinal-strip method of insulation are described, together with details of tests, strand shielding and thermal problems.

DOI:10.1049/pi-2a.1953.0037

出版商:IEE    

年代:1953

数据来源: IET

摘要:

An improved method of testing paper insulation for moisture by the measurement of dielectric dispersion over the frequency range 0.5–50 c/s or over the time range 3–300 millisec has been investigated. A direct-reading portable instrument giving immediately-significant results has been developed for dispersion testing, and its suitability for the testing of paper-insulated bushings, busbars, transformers and cables is now under investigation. An alternative method of detecting moisture in paper insulation which has been examined is the determination of non-linearity in the relationship between voltage and current. Although comparable with the dispersion method in sensitivity the non-linearity method has not been developed because of the greater difficulty in adapting it to field use.The testing of installed insulation for discharges in voids involves problems of interpretation and of portability. The nature of these problems is examined particularly in relation to a portable a.c. discharge detector developed for this kind of testing.

DOI:10.1049/pi-2a.1953.0040

出版商:IEE    

年代:1953

数据来源: IET

摘要:

The paper gives some specific instances of the wide variations which can occur in the measured electric strength of industrial insulating materials, arising partly within the material itself and partly on account of differences in the test conditions. Some of the results are subjected to an elementary statistical analysis.It is shown that short-time tests may be quite misleading as an indication of the relative merits in service of materials of different kinds, and it is concluded that the performance of a material can be found only by trial over a prolonged period. The paper includes the results of electric-strength tests at 50 c/s for periods up to two years, and these are compared with the results of tests lasting for only a few minutes.

DOI:10.1049/pi-2a.1953.0041

出版商:IEE    

年代:1953

数据来源: IET

摘要:

After the relative importance of the phenomenon of tracking has been mentioned and defined, the methods available for measuring the susceptibility of insulating materials to tracking are described. A simple test method is given which, it is suggested, could be adopted as standard test. By the use of this method, an examination has been made of some of the variables involved in testing for tracking susceptibility, in order to improve and assess the reliability of results.Attention is drawn to some further information which is required and which, it is hoped, will be soon forthcoming. In particular, the intra- and inter-laboratory reproducibility of the test method must be examined.

DOI:10.1049/pi-2a.1953.0042

出版商:IEE    

年代:1953

数据来源: IET