Engineering.

Progress, Volume VI, Issue 4, 1 February 1911, Page 546

Engineering.

Notes on Two Hydro - Electric Plants in Sweden. Paper read before the Canterbury College Engineering Society by W. Lancelot Moore. (Continued.) Automatic Governors. The governor proper consists of a pendulum distributing valve, servomotor, double return gear and hand regulating mechanism. The whole is contained in a compact cast-iron easing so constructed as to enable ready inspection. The speed of the turbine can be altered while the plant is running by means of a small hand wheel on the governor, or by a small motor, which is operated from the switchboard. This arrangement is very useful for coupling alternators in parallel as the switchboard attendant has all the machines under his control. The hand regulation device deserves special mention, as it is very simple, and effective. It is put in gear by simply pulling over a small lever, which at the same time cuts out the automatic gear. The pressure oil is supplied by a separate pump of the rotary type, which is connected to a large air vessel, which stores enough oil for 6 complete strokes of the servomotor. The pressure used is 1701 b per cubic inch. The y rav 2 of the generator is 980,000 kgm. The tests gave results shown by the table below and by diagrams taken by recording tachographs. These instruments are very sensitive, and the readings are correct within. a fraction of one per cent. The changes of load were effected by changing a -water resistance.

Electric Equipment. There are 3 3-phase generators of 3500 k.v.a., and 3 of 3950 k.v.a.; the pressure is 5000 volts, and the periodicity 50 cycles per sec. The full load efft. on test was 96 per cent., with a power factor 0.8. There are 2 exciters, each developing 225 b.h.p. at 600 r.p.m. The voltage is 220. Each sot is sufficient for the whole station, including lighting. The bulk of the power is transformed to 40,000 volts in 3-phase transformers, each of 3500 k.v.a. capacity. These are star connected on both the high and low pressure sides; they are of the usual water cooled oil type. Signalling thermometers are arranged to give alarm at the switchboard should the temperature rise unduly. The efft. on test was 98 per cent., with a p.f. 0.8.

The switchboard is arranged so that the generators may be connected directly to a transformer, or to a low pressure bus-

bar. The transformers arc connected in parallel on high pressure bus-bars, but these are divided in sections by switches. A view of the inside of the power-house was shown in our last issue. A certain amount of power is used in the immediate neighbourhood, hence the l.p. bus-bars. The switchboard proper is placed in a gallery overlooking the generators, but only- contains the necessary instruments, and operating handles all being worked at a harmless voltage. The 5000 volt system of bus-bars, switches, small transformers, etc., are placed in a small two-storied building outside the powerhouse proper. The main transformers, as well as the whole of the 40,000 volt system, are placed in two stories above the machine room. The separate phases of all bus-bars, cables and apparatus are separated by partitions of fireproof material. The distance between the 40,000 volt leads and earth is nowhere less than 10in., and between two phases nowhere less than 20 in. All switches consist of three single-pole switches of the oil type, which are separated by fireproof partitions. These switches are operated electrically from the switchboard, and are fitted with automatic tripping gear for overload or back surges. The oil switches may be cut out of the circuit by means of disconnecting switches operated by an insulating handle, should it be necessary to inspect or repair them. The generators and transformers are connected by steel armoured cables, the bus bars and all h.p. wiring are of bare copper. Each outgoing line is protected by two horn lightning arresters with a water resistance coupled in parallel with one of the spark gaps, and also by roller lightning arresters of the Gr.E.C. type, as well as water jet apparatus. About one-third of the power is consumed in the neighbourhood, the rest is sent out on two lines, one of which is 56 miles long, and the other branches out six miles from the station into two lines, one of which is 49 miles, and the other 42 miles long. The overhead lines are not duplicated; they are of bare copper, and are carried on wooden poles about 75yds. apart.

The whole of the work, from the very start, was completed within two years, which is very good, considering the severe winters in Sweden, and the fact that the work was never forced. The number of labourers varied from 120 to 800, and on an average 400 hands were employed. The minimum payment for unskilled labour was 4s. 6d. per day for earth work, and ss. 9d. per day for stone. Skilled labour was paid at from 9s. upwards. Approximately 110,000 cubic yards of stone were blasted out. The total cost, excluding only the transmission lines, and including the purchase of the water power, offices and housing, amounts to £252,000, which works out at Worn? = £9 per B.H.P.

Producer Gas from Refuse. During recent years many attempts have been made to produce gas for power purposes from waste factory products, and last month a successful trial was made in Sydney, scrap leather being used for this purpose. The method adopted was to treat the leather scrap by a special process which converts it into suitable fuel for gas producers.. The gas produced had a higher calorific value than that obtainable from charcoal or coke fuels, and the result of the experiment is regarded as highly satisfactory. Further trials are to be made this month, when a 50 h.p. gas engine and suction plant will be run for a week on the fuel mentioned.

Load on generator K.W. ... 3700 0 3250 1050 2450 Change of load K.W. ... -3700 + 3250 - 2200 + 1400 -1180 Change of load in % -100 + 100 -08 + 57 -50 Change of speed in % 118 G'8 5-8 3 2-8