The first attempts to transfer electricity over a distance. Part 1

Vienna International Exhibition of 1873

The first experiments on the transmission of electrical energy over a distance date back to the very beginning of the 1970s. In 1873, at the Vienna International Exhibition, the French electrician I. Fontaine demonstrated the reversibility of electric cars.

One of the machines Gram worked in the generator mode, and the same second - in the engine mode. The last machine operated an artificial waterfall water pump.

Wanting to reduce the engine power a little (so that the water did not break out of the pool), Fontaine decided to increase the resistance of the wires connecting the two cars. To do this, he switched on between the machines a drum with a cable a little more than 1 km long.

Thus, the possibility of transmitting electric power to a distance that was more or less significant by the representations of that time was shown. At the same time, Fontaine himself was not convinced of the economic feasibility of electricity transmission.

Since when connecting the connecting cable, it received a significant reduction in engine power, which indicated a large loss of power in the cable.

If we assume that it is required to transfer a certain power to a distance, then from the Joule-Lenz law it is seen that the losses in the line depend on the voltage, the resistivity of the wire and its cross section. Reducing the resistivity of wires is practically impossible, since copper, which has become the main material for the manufacture of wires, has an extremely low resistivity. Consequently, there were only two ways to reduce the losses in the line: an increase in the cross-section of the wires or an increase in voltage.

In the 1970s, the first path was investigated, since the increase in the cross section of conductors seemed to be an exercise, apparently more natural and technically more feasible in comparison with an increase in voltage.

Experiments on the transfer of electrical energy Pirotsky

In 1874 the Russian military engineer FA Pirotsky came to the conclusion that it was economically expedient to produce electric power in places where it could be cheaply obtained by the availability of fuel or hydraulic energy and transferring it along the line to a more or less distant place of consumption .

In the same year, he began experiments on the transfer of energy at the artillery range of the Volkov field (near St. Petersburg), using the electric machine Gramm. The transmission range in the experiments of Pyrotsky was first more than 200 m, and then was increased to about 1 km.

To reduce losses in the line, Pyrotsky proposed using railroad rails as conductors, the cross section of which was more than 600 times the cross section of an ordinary telegraph wire.

In an attempt to verify his conclusions, in late 1875 he experimented with the transfer of electricity along the rails of the inactive branch of the Sestroretsk railway about 3.4 km in length. Both rails were isolated from the ground, one of which served as a straight line, the second as a return wire. The electric current was coming from a small generator of Grams to an electric motor, remote at a distance of about 1 km.

It should be noted that Pirotsky was not the only electrician who had taken the path of increasing the cross-section of wires. For example, V.Siemens, having visited Niagara Falls in 1876, was able to correctly assess the energy possibilities of its use, but argued that to transfer the energy of the waterfall to a distance 50 km will require a conductor with a diameter of 75 mm. Similar conclusions were a clear expression of the level of knowledge in the field of electrical engineering in the 70s of the XIX century.

Despite the irrationality of the practical direction chosen by Pirotsky, his experiments drew attention to issues of electricity transmission in general, led to a number of new studies that led to the identification of the correct way to solve this problem.

Pyrotsky's proposal to use railroads for the transmission of electrical energy for a distance found its application already in the development of the first projects of urban electric railways.

Transmission by increasing voltage

Another way to solve the problem of electric power transmission, based on increasing the voltage of the transmission line, is the progressive path, was elected by the French academician M. DePre and DA Lachinov, a professor of physics at the Petersburg Forest Institute .

In March 1880, in the protocols of the Paris Academy of Sciences, a report was published by M. Despres on the efficiency of electric motors and on the measurement of the amount of energy in an electrical circuit, in which he mathematically proved that the efficiency of an installation consisting of Electric motor and transmission line, does not depend on the resistance of the line itself.

Such a conclusion seemed to be paradoxical to Dépre, as he initially failed to establish that an increase in line resistance does not affect the efficiency of power transmission only under a certain condition, namely, with increasing transmission voltage. These conditions were first indicated by prof. DA Lachinov in the article "Electromechanical work", published in June 1880 in the first issue of the journal "Electricity".

On the basis of mathematical calculations, Lachinov showed that in power transmission, "useful action does not depend on distance" only if the speed of rotation of the generator is increased (that is, with increasing line voltage, since the emf developed by the generator is proportional to the rotational speed ).

M.Deprea is a great merit in the practical solution of the problems of energy transfer by direct current over considerable distances. Proceeding from the previously developed principles, Desprex in 1882 is building the first Miesbach-Munich transmission line with a length of 57 km.

At one end of the experimental line in Misbah, a steam engine was installed, which activated a constant-current generator with a capacity of 3 liters. With., Giving a current of 1.5-2 kV. The energy was transmitted via steel telegraph wires 4.5 mm in diameter to the exhibition site in Munich, where a similar machine was installed that operated in the electric motor mode and activated the pump for an artificial waterfall. This power transmission worked intermittently (4 days out of 12) due to various network failures; Its efficiency did not exceed 0.25.

Although this first experience did not give sufficiently favorable technical results, its significance could not be underestimated: the Miesbach-Munich power transmission was the starting point for further work on the development of methods and means of transferring energy over a distance.