Together with the synopsis the conclusion of the lecture is given herewith.
The lecture is not an anouncement of the result of researches conducted, but a brief report of those which impressed the speaker most in relation to the question of the Power Transmission Line while he was recently travel-ling over Europe and North America.
The United States of America.
Since a report in details was made here a short time ago upon various electrical activities of the country, only a syllabus of the Super Power Zone is given, as an illustration of most recent and striking feature of the trasmission problem of that country.
However the scheme is still an idea upon paper c my and nothing yet has been carried out in reality (See Fig. I). In that country there is the experience of the transmission line up to 150, 000 volts for a reasonably long period.
France.
The transmission problem of France has been brought about by dual. purposes, namely electrification of her railway system and reclaimation of the desolated region caused by the Great War. The network of the power trasmission lines of the country are illustrated by Fig. II. The lines above 100, 000 volts no power has yet been transmitted through; they appear still as a plan.
Sweden.
In Sweden as shown in Fig. III, the transmission line of 130, 000 volts has been planned in an attempt to unite hydrolie powers of the Middle Section to that of the Southern Section of the country. There is no transmission line above 100, 000 volts in actual operation.
Germany.
There is 110, 000 volt transmission network in the vicinity of Berlin, as illustrated in Fig. V. In Bavaria, (Fig. IV.) an extensive scheme at same voltage is now under construction Indeed, Germany has good expe-rience in high tension transmission lines.
Switzerland.
Although, as shown in Fig. VI. 120, 000, volt transmission system has. been planned, she has still no experience of operating transmiting power of 100, 000 volts and upward.

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First the author briefly describes the main causes of abnormal voltage in transmission systems and discusses some of the defects of lightning arre-sters now in general use. Next the author criticises the recent trend in European practice in connection with the protection against abnormal voltages in high voltage transmission systems, and a short account is given about the prominent features of Petersen coil and similar devices.
The author is of opinion that it is almost impossible to adopt dead ground system for high voltage system in our country owing to considerable ind-uction effect on the communication circuits, and recommends the coil-ground system because of its favourable features of suppressing arcing ground and its least induction effect on the weak current circuits in comparison with the other systems.

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When the neutral of the transmission circuit is grounded through a reac-tance, there is a danger of abnormal voltage caused by the unbalance of each phase. In the case of the Petersen coil, since the iron core is used, the reactances changes its magnitude with the intensity of the current. In such a case, the voltage across tho Petersen coil, namely the voltage be-tween the neutral and the earth, is theoretically equal to the terminal voltage of the reactance of the equivalent circuit shown in Fig (2). Therefore the study of the equivalent circuit mentioned above is sufficient for the discu-ssion of the resonance problem in the actual transmission circuit.
If the volt-ampero curve and the phase difference of the reactance coil is given, the voltage across the reactance in the equivalent circuit is obta-ined graphically, though the process is slightly cumbersome. The voltage across the reactance expressed as a function of the impressed voltage is shown in Fig (3), there is certain unstable region which is represented with the dotted line. It is known from this graphical analysis, since there is certain loss (ohmic loss aud iron loss), if the impressed voltage is less than the critical voltage, there is no danger of abnormal voltage.
According to several expermients performed by the author, the actual obse-rved terminal voltage of the reactance agrees fairly well with that obtanied by the graphical analysis.
The author concludes that in ordinary transmission circuit the residual voltage will be sufficiently small, less than the critical voltage, therefore there will be no danger of abnormal voltage caused by the resonance, when the Petersen Coil is used.

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In discussing the performance and determining the capacity of the Pete-rsen earth coil, the calculations are first of all necessitated. In this paper the earthing current of a 150 kilovolt 140 mile transmission line is compu-tated, to find out that this current is not more different than 10%, accor-ding to the variation of the positions of the earthed point. The necessary capacity of the Petersen Coil for this line is found to be 90 K. V. 115 amp. per circuit. Next the abnormal voltage due to resonance of the coil was calculated, and the value was found to be limited by inserting 50 to 100 ohm resistance in series with the coil. Finally the estimation was made how the transposition of the overhead lines effects on the unsymmetric voltage of neutral point, which proved that two complete turns & more along the whole length of the line are sufficient for practical purpose.

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This paper is a detailed description of the method mentioned already in the author's previous paper to calculate the electromagnetically induced voltage on the weak current line by the accidental grounding of the power line. The assumptions upon which the autor's calculation is based are as follows:-
1. The current distribution within the earth crust is always determin-ated, independent of the nature of current, power current or charging current.
2. The electromagnetically induced voltage per unit length of the weak current line at any point is proportional to the magnitude of the current at the opposite point on the power line.
First the auther explained the current distribution when one line of the isolated 3-phase system is accidentally grounded, assuming that the line is free from impedance. Fig. 2 is the case when the ground occurs at the sending end, Fig. 3 the case when the ground occurs at the receiving end, Fig. 4 that for the intermediate point.
Based upon the prescribed assumptions, the electromagnetically induced voltage of the weak current line, of equal length with the inducing power line, as a function of the distance x of the ground from the sending end, is shown in Fig. 5. Thus when the ground occurs at the middle point, the total electromagnetically induced voltage becomes null.
If the neutral is ground with the Petersen earth coil, the total induced voltage becomes independent of the position of grounl as shown in Fig. 7.
If the neutral is ground with a non-inductive resistance having the same ohmicity with the Petersen earth coil, the total induced voltage increases greatly as shown in Fig. 8. x represents the position of ground on the power line from the sending end.
Finally the author calculated for the case, when the induced line is of the quarter length near the receiving end. In this case when the ground occurs at the receiving end with isolated neutral the total induced voltage becomes 7/16 E0, with the Peterson earth coil 1/16 E0, with non-inductive resistance 10.7/16E0.
As the remedy for the electromagnetic inductive interference, which constitutes a serious complaint in Japan, the Petersen earth coil seems to be very promising.

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A bifiler non-reactive coil usually gives a condensive reactance at high frequency. In the present paper this frequency error is absorved at audio-frequency range. The impedance characteristic is shown which resembles to that of an electric cable. From this experimental fact, a cable theory of a bifiler non-reactive coil is deduced. Employing an experimental cons-tant, which the authors call apparent dielectric constant, a method for des-igning a bifiler coil is given by this theory. A practical example of the design of a 100, 000 ohm coil, which gives a phase angle less than 5° at frequency of 5000, is given, assuming the apparent dielectrie constant to be fine.

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