Lauffen-Frankfort Line and Oil Insulators

THE LAUFFEN-FRANKFORT TRANSMISSION

The electrical even par excellence of the year 1891, was undoubtedly the successful accomplishment of the transmission of power by alternating currents of high potential between Lauffen and Frankfort, a distance of some 112 miles. The special committee appointed to test this installation have not yet made their official report, but the interest with which the large body of electrical engineers has followed these experiments is such as to warrant us in bringing forward a preliminary statement of the results obtained at Frankfort, as they appear in an article in the Schweizerische Bauzeitung by Mr. Emil Huber, director of the celebrated Oerlikon Works. According to Mr. Huber, the average potential used in the experiment was 16,000 volts, and only towards the end of the experiment was it increased to 30,000. The fears at first expressed that the oil insulators would not stand this pressure proved groundless, for as an actual fact only a single insulator broke down, and that under a strain of 30,000 volts.

Two other disturbances were caused by the breaking of a wire and by a defective insulator, due to a fault in the manufacture, respectively. It is interesting to note that the cost of the installation per effective horse-power - on the assumption that 300 h. p. was delivered to the line at Lauffen, and that the whole amount of this energy was available in Frankfort - was $300, of which the line itself involved a cost of $210!

But the next most interesting question from the electrical engineer's standpoint is that of the efficiency of transmission obtained in the Lauffen-Frankfort installation.

During the experiments, regular readings were taken at both ends of the line, and voltmeter readings were taken between one conductor and the neutral point in each of the three circuits, which averaged 54 volts, the currents reading 500, 490 and 500 amperes respectively in the primary circuits. Leaving out of consideration the lag between the current strengths and the potentials, the mean electric power delivered to the line was 80,500 watts. At the same time, the Frankfort end of the line delivered current for 1060 incandescent lamps of 16 c. p., which absorbed 58,000 watts. According to this estimate, therefore, the installation showed an efficiency of 72 per cent. Mr. Huber, however, points out that in reality the efficiency was actually higher, due to this lag, and he estimates it to be about 5 per cent.

Regarding the doubts which at one time expressed as to the influence of rain and foggy weather, it was shown that these phenomena had no material influence on the working of the line, no direct leakage to earth having been observed, the instruments showing the same indications both in wet and dry weather; so that, if there actually was such a loss, it was negligible. The losses due to condenser action of the insulators were also found to be but very small. In general it is claimed that no abnormal phenomena were developed in this transmission which could not be calculated and allowed for in advance for any similar installation to be made in the future, and that the losses are similar to those occurring in low-tension systems and which can be determined by Ohm's law.

In the absence of the official report of this installation, the results, as stated above, coming as they do from an interesting party, must still be considered of a tentative nature, but if they should be substantiated by the official report of the commission, the Lauffen-Frankfort transmission may well claim a high place among modern feats of engineering.