POWER SUPPLY OF AGRICULTURAL AREAS FROM HIGH-VOLTAGE NETWORKS

V. K. Shcherbakov

1. The electrification of the agricultural areas of the USSR is a most important task in the overall plan for the construction of socialism in our country. In the coming years, a large part of the regions of the USSR will be areas of complete electrification. The mechanization of agriculture increases, from year to year, the specific and absolute consumption of electric power in electrified agricultural areas. The enlargement of collective farms and the construction of new large villages and agro-towns impose additional and greater demands on electric power.

As a rule, the production of electric energy in agricultural areas is conceived on the basis of the use of local energy resources. The energy of small rivers must be used for the construction of a wide network of hydroelectric power stations. Many hydroelectric power stations for the power supply of agricultural areas of the USSR have already been built; each succeeding day brings news of the commissioning of new hydroelectric stations, but the degree of utilization of the hydropower of small rivers is still far from sufficient. Local fuel resources, and especially peat, are still little used. The possibilities here are great.

Enlarged collective farms build power stations of considerable capacity, and the radius over which consumers are covered by such power stations (with capacities of several hundred kilowatts) in individual cases reaches many tens of kilometers. Sometimes, according to the geographic and economic conditions of the area, district collective-farm power stations are built, supplying an entire district and even several districts within a radius of up to one hundred kilometers. In these cases, electric power is distributed by high-voltage networks, with voltages of up to 35 kilovolts.

2. District power stations have a whole series of advantages over small stations with respect to the utilization of equipment installed at the power station, efficiency, the standard of operation of the equipment, reliability of operation, etc. They make it possible to use large mechanisms on individual collective farms and at local enterprises.

The cost of electric power at a large power station is usually lower than at small power stations. If the construction of a district power station is carried out using local materials and labor supplied by collective farms, and if the operation of the district power station is ensured by local energy resources, then preference should always be given to the construction of an enlarged power station—of several hundred or even a thousand kilowatts—since the above-mentioned advantages of large power stations are obvious, and these advantages offset certain additional expenditures for the construction of high-voltage networks connecting consumers with the district power station.

In many cases, when the presence of energy resources on collective farms (small rivers, peat, wood waste, resins, etc.) creates unquestionably

favorable conditions for the construction of small kolkhoz power stations, it is advisable to combine the power stations of individual kolkhozes for parallel operation, for the purpose of mutual reserve and of increasing the effectiveness of the use of the installed capacity at the power stations. The operation of such a small system will be incomparably more reliable if there is in the system at least one larger power station in the district. If the advisability of combining kolkhoz power stations, especially thermal ones, with hydroelectric power stations in one case or another is beyond doubt, and, consequently, high-voltage connections arise for this reason, then the construction of a district power station (a base station) will in most cases certainly be advisable. A base district power station of several hundred kilowatts will make it possible to create stable parallel operation of kolkhoz power stations, whose capacity often amounts to only a few kilowatts or tens of kilowatts. It will take up possible overloads of kolkhoz power stations when the capacity of the latter is insufficient for the production and other needs of the kolkhoz, and in other cases the district system will be able to absorb any surplus capacity of one or another kolkhoz power station.

3. The question of the power-supply system of steppe districts that lack their own energy resources arises in an entirely different way. There are such extensive steppe districts, of great national-economic significance from the point of view of the production of agricultural products (for example, Kulunda in Western Siberia), where there are almost no small rivers, no peat, no forests, and no deposits of local coals and shales. In this case it is necessary, of necessity, either to bring in fuel from afar for electrification purposes, or to obtain electric power from a large thermal or hydraulic power station located at a considerable distance from the consumers.

If it is an indisputable fact that the electrification of some area, for example Kulunda, can be carried out only on imported fuel, the question arises of the most expedient use of this imported and, consequently, expensive fuel.

There can be two solutions to the question: 1) the construction of comparatively small thermal power stations for the needs of individual kolkhozes or groups of kolkhozes, and 2) the construction of large district power stations serving districts within a radius of several hundred kilometers. It seems to us that the second path—the path of constructing large district power stations—is the more correct one.

A large power station, with a capacity of ten thousand kilowatts and more, has an incomparably higher efficiency, and provides an electricity cost considerably lower (often several times lower) than small power stations.

A district power station can be built near a railway, whereas small power stations, scattered over a large territory, make it extremely difficult to deliver fuel from the railway to the power stations. Many other advantages of producing electric power at a large power station over producing electric power at small power stations may also be indicated: convenience in planning and using electric power, reliability of operation of large units equipped with all means of protection and control, a sharp reduction in fuel losses during transportation, etc.

4. But the larger the power station, the farther it is from the consumers, and the more complex and expensive is the electrical network connecting the power station with the consumers. Assuming that the power station of an enlarged kolkhoz should have a capacity on the order of 100 kilowatts, one should compare the cost of electric power in two cases: 1) electric power is produced at a kolkhoz power station with a capacity of 100 kilowatts; 2) electric power

is produced at a large district power station and delivered to the collective farm over a distance on the order of 200 kilometers.

The cost of producing one kilowatt-hour at a small thermal power station operating on transported fuel is many times lower than the cost of producing one kilowatt-hour at a large power station (with a capacity of more than 10,000 kilowatts). The transmission of one kilowatt-hour over a distance of 100 kilometers, along a 110-kilovolt line with a capacity of 5,000 kilowatts, and the further delivery of one kilowatt-hour to the collective farm can probably be accomplished at a cost of 50% of the cost of a kilowatt-hour. Thus, there is complete confidence that the cost of one kilowatt-hour for the consumer on a collective farm, with centralized production of electric power, will be lower than in the case of supplying the collective farm from a small power station. In considering the present question, it is also necessary to take into account, on the one hand, the additional expenditure of nonferrous and other metal for the construction of the high-voltage distribution network under centralized power supply and, on the other hand, the resources and effort required to transport, over tens and hundreds of kilometers—obviously by motor transport—fuel to small collective-farm power stations, plus all the difficulties and inconveniences of supplying consumers from a low-capacity station (lack of reserve, limitation of motor power, etc.).¹ When comparing, say, one 10,000-kilowatt power station with a hundred small power stations, one must bear in mind the consumption of gasoline for transporting fuel from the railroad to the collective-farm power stations in an amount of about a thousand tons per year.

Undoubtedly, the advantages of supplying agricultural consumers with electricity from high-voltage networks will increase still more if the electric power is obtained through the use of hydro resources.

Fig. 1

A single large hydroelectric station, or a cascade of hydroelectric stations built in the vicinity of the area to be electrified, can eliminate the need to obtain electric power from transported fuel. Electric power from a large hydroelectric station is usually several times cheaper than electric power obtained at a thermal power station. Therefore the radius of coverage by electrification from high-voltage networks fed by a hydroelectric station can be increased, say, to 300 kilometers.

Thus, the electrification of agricultural districts that are of great importance to the national economy and lack local energy resources should evidently be carried out from large district power stations, using high-voltage networks of considerable length. In this connection it is important to foresee in advance the necessity of changing over to voltages higher than 10 kilovolts. Figs. 1 and 2 show, approximately, the zones of transmission voltages for the conditions indicated in the figures, depending on the transmitted powers and the length of the lines.

Fig. 2

Fig. 2 emphasizes the necessity of changing over to a nominal voltage of 110 kilovolts in the power supply of agricultural districts from high-voltage networks with a radius of coverage of 100 or more kilometers.

Practice has established that the use of three-phase transmission lines operating according to the “two wires—earth” system, at voltages up to 35 kilovolts, gives significant economic advantages. It is probable that networks with a nominal voltage of 110 kilovolts should also be built with one grounded phase. The proposal by engineer Andreev (“E-vo,” No. 3, 1952) on the use of double “DPE” lines eliminates the substantial drawback of lines with a grounded phase—the current in the earth.

The question remains unclear as to the possibility of using 110-kilovolt transformers of ordinary design in a grounded-phase operating mode without special reinforcement of these transformers. The same applies to line insulation, although some data on this question are already available¹.

The use in agricultural districts of networks with a nominal voltage of 110 kilovolts cannot be restricted because of the absence of transformers for this voltage with capacities of one thousand or fewer kilovolt-amperes. Such transformers should be manufactured by the electrical industry, since the need for them is evident.

1. V. K. Shcherbakov, “Lines Using the Conductor of One of the Phases Also as Protection against Lightning Strikes,” Proceedings of the Tomsk Polytechnic Institute, vol. 59, 1940. ↩↩