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Volume 47, Issue 468
Displaying 1-8 of 8 articles from this issue
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E. FUKAO1927 Volume 47 Issue 468 Pages 673-691
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSIn the high voltage transmission line whose neutral point is grounded, if there occur an accidental ground on one of the conductors, a heavy short circuit current will flow through the earth, inducing a voltage in the neighbouring communication lines by the electromagnetic action. In some cases, the voltage thus induced in the communication lines may reach to such a dangerous amount as to destroy the apparatus connected to the communication lines or to effect a heavy accoustic shock to the telephone operators. In Japan, especially, the geographical circumstances does not permit to leave a sufficient distance between both the power and the communication lines.
The investigation and field surveys have been continued for more than ten years by many electrical engineers under the auspices of the Engineer in Chief, Bureau of Electricity, Ministry of Communications, together with those of the various power companies, whenever the main transmission lines have been completed ; the results thus obtained will be described in this paper, having the contents as follows,
(1) The reasons why this problem must be considered as an important one in our country,
(2) The formulae for the calculation of the electromagnetic incuced voltage in the communication line are stated, quoting the Dr. Shibusawa's(1) formulae and the formula proposed by the Verband(2) Deutcher Elektrotochnikers,
(3) The method of actual measurement of the electromagnetic induction and the result are shown,
(4) In our test results, these are several points of which we must take care, for examples, the relations between the magnitude of the electromagnetic induced voltage and that of the inducing current through the earth, or the frequency of the inducing current,
(5) Comparison of the actual results with the calculated ones,
(6) Conditions of proximity between both the power and the communication lines in our country are described,
(7) The magnitude of the electromagnetic induction is seemed to depend on the geological circumstances and the localities where the power and the communication lines pass,
(8) Considering the relations shown in (7). and from our test results the author proposes a new formula for a time being which would become to be modified in the future by the further experiments,
V=KfI∑l1/b1
where V=the induced voltage in the communication line, in volts,
f=the frequency of the current through the earth or the inducing current,
l1=the length of a portion of the power line, in meters,
b1=the distance between both the lines, in meters, when they are parallel. If they are not parallel, the arithmetic mean of the extreme two distances perpendicular to the power line, as shown in Fig. 13,
K=a constant depending on the geological conditions of the district where both the power and the communication lines pass, and it will be approximately as follows in our country,
i. Mountain district K=(0.5 to 0.8)×10-3
ii. Plain district K=(0.25 to 0.4)×10-3
but the magnitude of the induced voltage is seemed to be different according to the localities where the lines pass, in the numerical values of K shown above, 0.5 and 0.25 are the values in the mountain and the plain districts respectively in one locality, while the values 0.8 and 0.4 are those in another locality,
I=the short circuit current through the earth of the power line, in amperes,
(9) In Japan, we have not met with difficulties of the electromagnetic disturbances on the communication lines due to the power lines.
(This paper has the same contents as those in the "Report on the Electromagnetic Disturbance on the Communication Line due to an Accidental Ground of the Power Line" by S. Mayebare and E. Fukawo, presented to the Fourth Session of the International Congress of Extra High Tension Network, which will be held in Paris this year)View full abstractDownload PDF (1003K) -
Juichi OBATA1927 Volume 47 Issue 468 Pages 692-708
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSFrom the experience obtained in manipulating cathode-ray oscillographs of Johnson and Wood types a comparison is made of the three types of the oscillographs-Johnson, Wood and Dufour types-, which have been recently put on the market.
Among these cathode-ray oscillographs, the one which has high electrical sensitivity lacks in photographic sensitivity, while the one which exhibits very high photographic sensitivity is very insensitive electrically. Thus, none of these oscillographs cannot be said still to be ideal. Owing to the nature of cathode-ray, it is undoubtedly a matter of considerable difficulty to make both these sensitivity high enough at the same time, yet the cathode-ray oscillograph at its present state of development is far from being satisfactory, its use being limited to a certain kind of problems.
Finally, mention is made on a peculiar photographic phenomenon obtained with the Wood type oscillograph using Schumann plate sensitised with calcium tungstate.View full abstractDownload PDF (1478K) -
M. TAKATA1927 Volume 47 Issue 468 Pages 704-710
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSThe auther investigated the rather antique problem of "The Minimum Cost Transformer" from a new standpoint of view, and concluded that the problem exists scarcely any longer, when we design the transformer under conditions accustomed to be given by the orderer now-a-days.View full abstractDownload PDF (386K) -
Lead Covered Cables by the Dynamometer WattmeterH. NUMAKURA1927 Volume 47 Issue 468 Pages 711-719
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSIn Measuring total dielectric loss of the plain three phase lead covered cable, there may be two modes. One of them is to measure the dielectric loss under working conditions, that is, at three phase voltage. The other is to measure it between cores and sheath and among three cores at single phase voltage. The author has measured the dielectric losses of several plain three phase cables at various voltages by these two modes using the dynamometer wattmeter. He compares those results in this paper. Generally the values of dielectric losses measured at three phase voltage are a few per cent greater than those measured at single phase voltage.
The cause is thought to be owing to the rotating electrostatic field produced in the dielectric under three phase conditions.
Therefore, strictly speaking it is better to measure the dielectric loss at three phase voltage. But measurement made by the dynamometer wattmeter is expected to contain considerable errors, because very accurate compensation of pressure circuit is very difficult. For that reason, the author describes that in measuring dielectric losses of the three phase cables single phase voltage will suffice practically.View full abstractDownload PDF (541K) -
S. Kato1927 Volume 47 Issue 468 Pages 720-728
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSRotary converters, when started from a.c sides, have no fixed polarity in d. c. brush voltage, the residual magnetism being destroyed by the alternating magnetisation of armature reaction at starting. The author designed a converter of new opinion whose magnetic circuit (Yoke and poles) is made of magnetic materials of high coercive force, such as magnet steels, and shows, in this paper, that this machine, under a certain conditions, synchronizes automatically without field excitation, with a fixed d. c. polarity as in a d. c. generator, at induction starting.View full abstractDownload PDF (2586K) -
Takabumi KUMAZAWA1927 Volume 47 Issue 468 Pages 731-742
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSStudied experimentally the electro-magnetic effects caused by the hunting of the motor.
Conclusions obtained are as follows:-
(a) hunting increases the input current-
(b) it decreases the power.
(c) curve showing the relation between the mechanical amplitude of hunting and the increase of input current, is similar to the magnetisation curve.
(d) for three phase motors, there are three different mechanical amplitudes of hunting and coresponding input currents, even if the impressed emf and exciting current are kept constant.
(e) mechanical hunting is followed by the same phenomena in phase angles.
(f) several other phenomena are also observed in armature reaction.
The writer proposes a way to explain some of the above mentioned items, as the decrease of effective value of d.c. field owing to the hunting.View full abstractDownload PDF (700K) -
M. TAKAHASHI1927 Volume 47 Issue 468 Pages 743-774
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSA brief survey of the existing super-tension under-ground cable installations in Europe and America with a working pressure of over 30, 000 volts each, and comparisons between equipotential H type cables and normal type cables. In regard to aerial conductors the writer specially referred to the actual condition attending the use of copper wires, steel core aluminium cables, and hollow cables, for super-tension aerial lines.View full abstractDownload PDF (2672K) -
1927 Volume 47 Issue 468 Pages 774
Published: 1927
Released on J-STAGE: November 20, 2008
JOURNAL FREE ACCESSDownload PDF (62K)
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