TEANSACTIONS OF SECTION G. 873 



As it is sometimes necessary to put repeaters in on the Englisli side of the 

 cable on some lines which nominally work direct to the Continent, the resistance 

 blocks on several of the instruments are wound to 1,000 ohms, and fitted with a 

 switch which enables either 100 ohms or 1,000 ohms to be inserted in the battery 

 circuit, and thus the current is kept constant. In addition to the independent 

 three-ampere fuses main fuses to break at ten amperes are placed on each group 

 of circuits in the accumulator room. 



All the coils are kept well charged, and the E.M.F. is not allowed to fall 

 T)eIow 1-95 volt per cell. Where spare or reserve sets are provided the charging 

 is carried on at any convenient time, and on those where no spare is in use the 

 charging is done at night, when the minimum disturbance is caused by the slight 

 increase of E.M.F. which is inseparable from simultaneous charging and working. 



Accumulators are also used for working the Paris telephone circuits. Their 

 E.M.F. is so constant that they are found to be eminently adapted for the 

 purpose. 



4. Power Transmission hij Alternating Current. Bij Gisbert Kapp. 



Some two years ago the municipal authoritier. of Cassel, in Germany,determined 

 to become purveyors of electric light, and to place the generating station on the 

 site of the waterworks pumping station, which is situated on the river Fulda, about 

 four miles from the town. The object in choosing this site was partly to bring 

 both undertakings under the same management, and so reduce administrative 

 expenses, but chiefly to utilise an existing turbine plant. 



Owing to the great distance between the generating station and the town, it 

 was necessary to work at high pressure and to use some system of transformation 

 in the town, whilst to make the best use possible of the existing power plant it was 

 necessary to combine with the supply some system of storage. This problem was 

 solved in a very successful manner by a German engineer, Herr Oskar von Miller, 

 who had been called in by the municipality to carry out the work. The plan 

 adopted by von Miller was briefly this. He determined to transmit power by 

 single phase alternating current from the generating station to a sub-station or 

 rather to two sub-stations in Cassel, and to use this power for the supply of direct 

 current on the three-wire system. At one of the sub-stations he established a 

 battery which is charged during the hours of light load, and assists the dynamos 

 during the hours of heavy load, so that the maximum power available shall suflice 

 for ;3,500-60-C.P. lamps wired. 



At the generating station are two 60 K.W. alternators, which can be used 

 singly or in parallel, and the current is transmitted through an underground con- 

 centric cable over a distance of about four miles to the sub-stations. The alterna- 

 tors are designed for a terminal pressure of from 2,000 to 2,200 volts, and the 

 loss of pressure in transmission, when both are working full power, is under 10 per 

 cent. 



Each sub-station contains an alternating continuous current transformer, con- 

 sisting of a 60 K.W. alternator, coupled with two continuous current dynamos, one 

 on either side. The latter machines are connected with each other and with the 

 mains in the usual way adopted in three-wire distribution. At one of the sub- 

 stations there is a battery, also arranged on the three-wire system. The mains 

 throughout the district are coupled so that the battery sub-station can supply 

 current to the other sub-station through the town mahis. To start any one of the 

 two transformers it is only necessary to switch on the two dynamos which begin to 

 work as motors, and, alter observing by a synchroniser that the speed of the 

 alternator has reached the required amount, to close the high pressure alternating 

 current switch, when the alternator works as a motor supplying power to the two 

 dynamos which are directly coupled to it. It will thus be seen that not only are 

 the two alternators at the generating station worked in parallel, but also the two 

 sub-station alternators erected in different parts of the town are worked iu parallel. 

 The dynamos are Brown's design and the alternators are my design, both made by 

 the Oerlikon Engineering Works, but I must distinctly state that I can claim no 



