The rivers of Sweden are inexhaustible sources of power which could be obtained otherwise only from imported fuel. The vast network of hydro-electric stations supplies electricity for the railways, industries and mines of the country
TROLLHÄTTAN POWER STATION is one of the largest in Sweden. The waters of the River Göta have been harnessed to drive thirteen great turbines. It was at Trollhättan that Dr. de Laval, at the end of nineteenth century, conducted his famous experiments in turbo-generation.
SWEDEN’S industries were, until recent years, carried on under considerable disadvantages. Except for one small coalfield in the province of Skane, in the toe of the Scandinavian peninsula, Sweden has no coal mines. Virtually the whole of her railway system was once dependent on imported coal. So were her great iron mines in the Bergslag (Central Sweden) and Norrbotten (Lapland) districts.
With the advance of electrical engineering during the twentieth century the Swedes have found that their country has compensation for her lack of coal. The compensation is found in “white coal” — namely, almost unlimited water power. A glance at a physical map of Sweden shows that the country has an unusual configuration. For the most part it is flat, but it is bounded on its western and northern frontiers by the long line of the great Scandinavian mountain chain. From this huge watershed numerous rivers flow down, right across Sweden, to find their outlets at the coast, chiefly on the Baltic Sea and the Gulf of Bothnia.
The rivers fall rapidly from the high hills, foaming down through the blue-green forest land that covers much of the country. Each of them contains an enormous amount of energy, waiting to be harnessed by the modern engineer. For uncounted ages those great streams have been pouring down from the distant snowfields, such rivers as the Great Luleå and the Angerman in the north, the Dal, which runs through the central mining district, the Klar and the Göta.
The Klar and the Gota are exceptions to the general rule of west-to-east flow. The Klar, or Klarälven, as it is called in Swedish, flows southwards from the mountain lakes in the Norwegian province of Hedmark, growing larger as it penetrates Swedish territory, and finally finding its mouth in Lake Vaner. The Göta, in its turn, flows out of the foot of Lake Väner, and runs to the Kattegat, an arm connecting the North Sea with the Baltic at Göteborg (Gothenburg). At Trollhättan, near Vänersborg, the Göta passes over a series of magnificent falls.
In addition to its great locomotive and machinery works, Trollhättan has one of the finest hydro-electric stations in the world. Sweden’s engineers have harnessed the Trollhätte Falls, and thus impounded the colossal energy of millions of tons of water which run continually out of Lake Väner on their way to the sea. Two other great power stations are situated in the relatively short valley of the Göta, one at Lilia. Edet, between Trollhättan and Göteborg, and the other, a recent installation, at Vargön, above Trollhättan and close to the town of Vänersborg.
The major hydro-electric stations of the British Isles, those on the River Shannon, in Galloway and in the Scottish Highlands, are easily enumerated. But in Sweden, whose national life has come to depend on this harnessing of natural energy, there are big power schemes all over the country.
Many of the Swedish State Railway’s main lines are now electrically operated and electric traction is still extending. Of the State Railways, which extend over the length and breadth of the country, more than 1,600 miles of route are electrically run. Among other railways, the Nordmark-Klarälven Railway has 101 miles of electrified route. On the State lines, it is possible to travel from Trälleborg, at the extreme southern extremity of the country, to Ånge, above the 62nd Parallel, by electric traction alone.
The Lapland Ore Railway is electrified and the Swedish Government is aiming at complete electrification from Trälleborg to Riksgränsen, on the Norwegian frontier over 100 miles north of the Arctic Circle.
Electrification has penetrated all the major industrial centres of Sweden. In the big Bergslags ironworks such as those at Grängesberg, Örebro and other places, in the great paper mills which use timber from Sweden’s vast forests, electricity reigns supreme.
Sweden is not merely one of the greatest producers of electricity and electrical machinery; she was also one of the pioneer nations. During the period 1880-90, Jonas Wenström, the first chief engineer of the Swedish General Electric Company, known as A.S.E.A. (Allmänna Svenska Elektriska Aktiebolaget), was rapidly developing the production of electrical energy and transforming and distributing current on the three-phase system. The company took over the patents in 1890, and Wenström continued to perfect and elaborate them. Wenström and his colleague Danielson produced, in 1893, so satisfactory a motor that in the same year the company contracted to build its first Swedish electric power transmission plant. This pioneer installation consisted of a generating station at Hellsjön, in the central iron district, with an output of 300 horse-power. Rather more than nine miles of transmission line conveyed current at a pressure of 9,500 volts to motors at Grängesberg. This plant was extraordinarily successful, and proof of Wenström’s skill lies in the fact that the original installation was still doing good work in 1937.
Wenström died in 1893, and Danielson carried on the work with A. Lindström. Through these men the great industry of A.S.E.A. became world-famous, and the three-phase system was brought to perfection. The success at Hellsjön caused a demand for the new type of electrical equipment, and before long the company was building generators in standard sizes with outputs varying from 3 kVA to 125 kVA at an approximate speed of 600 revolutions and 50 cycles. These early generators, similarly to those in the great modern power stations of Sweden, had rotating armatures and stationary fields, this arrangement having been inaugurated in the Hellsjön works.
RIVERS AND RAILWAYS OF SWEDEN
Porjus Power Station, in Norrbotten, and the peculiarities of power production in the subarctic regions are described in the chapter “Lapland’s Arctic Railway”. A more typical example of a great Swedish hydro-electric station is that at Trollhättan, on the Göta River. It was here in the eighteen-nineties that Dr. de Laval conducted his famous experiments in turbo-generation, which are an all-important milestone in the early progress of hydro-electrification. For de Laval, A.S.E.A. built one vertical generator in 1896, having an output of 850 kVA at 250 revolutions and 12.5 cycles, supplying current at a pressure of 300 volts. During 1897 de Laval continued his experiments at Trollhattan, and another similar generator was delivered to him.
After de Laval’s experimental station came the present installation, which has been extended in the course of the years, and which is owned by the Swedish Government. The original installation and equipment date from the first decade of the present century, and in 1909 four three-phase generator sets were installed, each having a continuous output of 11,000 kVA. Each alternator had a stationary armature winding within the stator casing (the huge cast-iron shell of the alternator) and a rotating field on a horizontal shaft directly coupled to the shaft of the accompanying water turbine. These initial alternators at Trollhättan were the first completely enclosed A.S.E.A. generators; in other ways also they were the prototypes of modern generators built by the same works for installations all over the world. When built they were among the largest water turbine-driven three-phase alternators in existence.
Between 1909 and 1918 nine more turbo-alternators of similar design, working at 25 cycles, were installed at Trollhättan, bringing the total number up to thirteen. In 1920 and 1921, a pair working at 50 cycles was installed in the station. Trollhättan supplies energy for traction and industrial purposes over a wide area of south-western Sweden, and a submarine transmission line carries current across the Kattegat for use in Denmark also, that country being deficient in water-power as well as in coalfields.
The whole aspect of the place is striking. Trollhättan differs in many ways from the typical mountain power station, where one of the most remarkable external features is the long line of flumes coming down from an adit set at a much higher level.
At Trollhättan the water for driving the turbines is led in from above the falls through a masonry forebay to the intake building, whence it is passed through to the thirteen great turbines. Huge sluices control the return of surplus water to the river and over the falls, which roar down their rocky gorge on the western side of the station. The machinery hall is a long stone building, of attractive appearance, set at right angles to the river. Inside, it is impressive to a degree. The rows of alternators and turbines extend down the long hall, alternators on one side and turbines on the other. Between them are the couplings and on the outside of the row of alternators are the exciters.
Turbines and alternators alike are covered by huge round casings, painted green. The alternator casings are, without exception, of cast iron. The designers chose this material for a number of reasons. Of stout box-section construction, giving great rigidity, the iron stator casings allow the hot air to pass away from the inside of each alternator with a minimum of trouble. The hot air is conducted out through ducts leading from the bottom of each casing. The use of cast iron makes possible a better fit, rendering the casings completely airtight and therefore soundproof.
Visitors to Trollhättan are often astonished at the relative silence of the machinery hall. There is no roaring or whistling, nothing but a steady and continuous hum. The impression which it conveys of tremendous energy under control is stimulating.
ELECTRIFICATION of the Swedish State Railways is one of the effects of the development of water power in Sweden. The Iron Ore Railway from Lulea to Narvik (Norway) was electrified by 1923. Four years later the main line from Stockholm to Goteborg (Gothenburg) was electrified. More than 1,600 route miles had been electrified by 1937 and the work continues.
Cleaning and inspection of the alternators do not, however, necessitate the taking down of the entire iron side shield. This contains small doors through which the electricians and engineers in charge can gain easy access to the interior. Even for thorough overhaul or repair it is not necessary to dismantle the whole machine. Once the end shields are removed the stator can
be moved out on slides; the engineers can thus examine and repair the coils in stator and in rotor without removing the rotor from its bearings.
The exciters mounted in conjunction with the alternators are operated on direct current supplied from a central source at a pressure of 220 volts. Each alternator weighs 191 tons complete, distributed as follows: stator and casing, 102 tons; rotor, 67 tons; bearings and bedplate, 22 tons.
The Trollhättan hydro-electric station enjoys a fine situation, and it is difficult to admit that the works spoil this in any way. Rather, the great efforts of man and Nature, side by side, tend to enhance one another. The buildings are architecturally good and the light stone of the masonry blends finely with the dazzling white foam of the falls, the grey of the rocks in the gorge and the dark green of the woods above. These great falls have their legends, originating in the misty past, and on the great dam is a sculptured face of the “Water Spirit”, which looks out over the scene from beneath rocky eyebrows, while its carved granite beard seems to flow down to mingle with the flashing foam below. A privately owned hydro-electric works of considerable interest is that at Bullerforsen, in central Sweden. It belongs to a mining organization known as the Stora Kopparberg Bergslags A.-B. (Great Copper-Mountain Mining Company), which is not only one of the biggest concerns of its kind, but also among the oldest joint-stock companies in the world. The company’s hydro-electric station at Bullerforsen derives its energy from the Dal River, from which the province of Dalarna receives it name.
Electric Rolling Mills
The Stora Kopparberg Company placed its first contract for the supply of electrical equipment for the works at Bullerforsen in 1908. In the spring of 1910 there were installed three three-phase alternators, each having a continuous output of 3,500 kVA at 7,000 volts, 60 cycles, running at 180 revolutions a minute. In 1912 the company decided to augment the plant, and installed another generator, the output being increased to 3,800 kVA. This output was made possible because the engineers found that they had. tapped a better water supply than they had at first anticipated. In 1912 two more generators were ordered, this bringing the number up to six altogether.
The design of the original generators was on a liberal scale, allowing for a margin of overload which permitted the increasing of their continuous output. The six generators, unlike those at Trollhättan, for instance, are of the open type without side shields, the whole of each rotor “spider”, or rotor centre, being visible. The stator casings are of cast iron, divided horizontally for removal when necessary and provided with ventilating holes on the periphery. The armatures are stationary, the fields being rotary. The appearance of these great open type generators is impressive, whether they are at rest with the eight great spokes visible, or in motion, when it is possible to see through the machine. Each generator weighs 61½ tons, of which 28 tons and 23 tons are contributed by the stator and rotor respectively, the remainder being made up by the bedplate and bearings.
THE “SPIDERS” OR ROTOR CENTRES of the generators at Bullerforsen Power Station are not enclosed in any form of shield. There are six generators of this type at Bullerforsen, each weighing 61½ tons, of which 28 tons are accounted for by the stator.
Most of the power produced at Bullerforsen goes to the Stora Kopparberg’s works at Domnarvet, where the great rolling mills are electrically operated. A portion is used for electro-metallurgy, operating the electric furnaces. Though now over a quarter of a century old, these works at Bullerforsen and the electrical power equipment at Domnarvet form one of the finest and most perfectly arranged installations in Sweden.
Another exceedingly interesting piece of industrial electrification in Sweden is that of the Uddeholm Company at Hagfors, on the River Klar in the province of Värmland. The Uddeholm Company was one of the first of the great iron companies in Sweden to produce large quantities of pig iron with electric blast furnaces, and as long ago as 1906 it decided to harness the energy of the River Klar for this and for other purposes.
The estimated water horse-power available at Forhultsforsen on the Klar was 21,000, and the engineers built their dam and power station on a scale intended to make full use of this source of energy. At first, however, only part of the potential supply of power was to be used, when three three-phase generators were ordered in 1910. These were erected early in 1911. Two years later two more were installed and the works was brought up to full capacity in 1916. In its final form, the station contained seven of these three-phase generators, providing a continuous output of 2,600 kVA at 12,000 volts and 187.5 revolutions a minute.
The war of 1914-18 caused a great and sustained demand for Swedish iron, and the Forhultsforsen station had been completed only a year when the owning company realized that the provision of yet more energy was essential. The river was working to full capacity there, and there was no alternative but to build an additional hydro-electric power station, higher up the valley, at the falls of Krakerud.
At this place, the generators are of the same general type as those at the slightly older station; they are of the open type with rotating fields and stationary armatures. There are three generators, two large ones designed for a continuous output of 4,300 kVA at 150 revolutions and 25 cycles, and one smaller generator with an output of 2,100 kVA, current being supplied by them at 12,000 volts.
An example of a more recent installation is Vargön Power Station, near Vänersborg, on the Göta River. Vargön is the nearest of the three Gota power stations to Lake Väner and, with those at Trollhättan and Lilia Edet, it belongs to the Swedish Government.
The power station serves two purposes: the supply of power, and the regulation of the flow of water out of the lake. It has been estimated that the average flow of the Göta River at this point is approximately 650 cubic yards a second.
The height of the natural fall here is about 12 feet, but alterations are being made in the river bed above the station to increase this height to 14 feet. The station itself is unusual in layout, as well as being notable for the fact that it contains what are probably the largest generating sets in the world. There are two main three-phase generators, each of the vertical type and each having a continuous output of 12,000 kVA at a pressure of 11,000 volts and a speed of 46.9 revolutions. These are driven by enormous spiral turbines, each using 431 cubic yards of water a second.
SLUICE GATES control the flow of the water into the turbines at Trollhattan from the River Gota. Above the power house the water is led to the intake building through a masonry forebay.
The designers of Vargön have adopted a unique arrangement, for there is no machinery hall here at all. The gigantic generators are mounted in the roof of the building, above their respective turbines, sheet metal housings covering the top of each. The control room lies between the two generator sets, on a level with the turbine regulators. The passages carrying the water through the turbines are designed on the siphon principle, with the gate valves high up. This allowed for a reduction in the blasting of the river bed during construction. The turbine runners are easy of access for examination. On top of the building, which is of concrete, are rails on which runs an immense gantry crane, having a lift capacity of 200 tons. This crane, which can travel up and down the whole length of the station roof, as well as out towards the left bank on two extension girders over a barge basin, has two swinging jibs, one on the upstream and the other on the downstream side. The metal housings covering the tops of the generators, which are straddled by the legs of the gantry, are removable.
On the eastern side of the station, the dam is pierced by four spillways, one closed by a simple straight sluice and the other three by sector gates. The two sector gates nearest to the generator house are remote-controlled from the Trollhättan station, lying farther down the river.
It is the slow speed of the Vargön generators which necessitates their being of so great a size. The exterior diameter of each stator casing is no less than 37 ft. 6 in. and the vertical height 6 ft. 3 in. The Vargön station forms an addition to the existing power system at Trollhättan, for which it acts as a regulator. For this reason it is arranged to be remotely controlled from Trollhättan, which station controls almost all the oil circuit breakers. This system of remote control is a wonderful installation. If Trollhättan is in control, and this duty is to be changed over to the control room at Vargön, a signal lamp lights up at Vargön, and Trollhättan also gives an audible signal. When Trollhättan once again takes over from Vargön, the process is reversed. It is not possible for the changeover to be made until these signals have been received in the station which is not originating the changeover. Those in control at Vargön may take over from Trollhättan in all conditions, but Trollhättan may take over only after Vargön’s engineers have transferred the duty on their own initiative.
Surplus Energy for Industry
In an emergency, Vargön Power Station can take over control of the circuit breakers without having to obtain the permission of Trollhättan. The Vargön station can, if necessary, block any one circuit breaker control by means of a switch inside the instrument panel, or even cut out the whole of the remote control system operated from Trollhätten through the manipulation of a knife-switch on this same panel.
One of the latest developments is the opening of the hydro-electric works at Krångede, in Jämtland. The works are designed to equal in output those of Trollhättan. Krångede inaugurates a new policy of tapping the surplus energy of the wild northern districts and transmitting it to industrial users in the south or middle-south of Sweden. The Krångede Works are situated, almost on the sixty-third parallel, on a natural fall of the Indal River, which flows down from a chain of lakes extending to the Norwegian frontier. A high-tension transmission line runs southwards to a substation at Horndal, in Dalarna, whence energy is transmitted to various industrial undertakings in the Bergslag district. Krångede also supplies energy for the northern trunk railway line.
It is difficult to convey in a short description the sense of unhurried efficiency characterizing any one of these great installations which are contributing so strikingly to Sweden’s prosperity and self-sufficiency.
In the whole wide field of modern engineering there can surely be few things more romantic than a system whereby the driving force for the machinery of a great nation is drawn more and more from the inexhaustible natural resources of the country. And nowhere, perhaps, can we see this happening to a greater or more complete extent than in the ancient kingdom of “the Swedes, the Goths and the Wends”.
TURBINES AND ALTERNATORS in Trollhättan Power Station are covered in huge casings painted green. The alternator casings are made of cast iron. Each alternator weighs 191 tons; the stator and its casing alone weighing 102 tons.