D.—i:

(6) Power-stations. Arapuni. Construction work at Arapuni during the year included the completion of No. 4 unit, and of the two auxiliary units (each consisting of one 550 h.p. turbine, one 450 kv.a. A.C. generator, and one 120 kw. D.C. generator, with an exciter for the A.C. generator mounted on the same shaft), the installation of one set of 50 kv. potential transformers for synchronizing, and of a 50 kv. neutral earthing transformer for the 110/50 kv. transformer-bank. Of these, No. 4 unit was placed in service on 16th May, No. 1 auxiliary set in June, and No. 2in August. Improvements were made to the outdoor station earth. Horahora. Improvements were carried out by the Arapuni Office to the concrete work below the weir, to repair the results of erosion and prevent further erosion. New 50 kv. line protection equipment was installed. (c) Transmission-lines. 110.000-volt Arapuni-Stratford Line.— This line will be about 123J miles long, with conductors of 19/-101 copper cable, carried on wood-pole structures for 78| miles from Arapuni to Tatu, thence for 40| miles on steel towers from Tatu to Toko, through the rough country near Tangarakau and Whangamomona, and to about four miles from Stratford substation, where, owing to the more level nature of the country, the wood-pole type of construction is again used. A telephone line parallels the transmission-line for its whole length. The erection work was commenced on the 15th October, 1931, but owing to the financial position it has not been possible or necessary to push it urgently, and the proposed date of completion now is April, 1934. At the end of the year the position was as follows :— Arapuni-Tatu Wood-pole Section : Of a total of 543 pole structures on this section, 518 have been erected and 494 wired. The telephone line (1,305 25 ft. poles) is complete. Tatu - Toko Steel Tower Section : Of a total of 191 towers on this section, 14 have been completed, the stubs and bottom sections of an additional 26, and the special " rock " stubs of 13 others, have been erected. Of a total of 582 telephone poles, 114 have been erected and 112 have been wired. Work has not yet been commenced on the Toko-Stratford section. Bush-felling and Track Construction : The bush-felling and burning required for the line has been done, and a total length of 8 miles 78J chains of 6 ft. track for cartage of material by tractor, and 1 mile 22| chains of 4 ft. track in the Tangarakau district has been completed. (d) Substations. Bombay.— -The original layout of this substation included only one 50/11 kv. transformer-bank of 1.500 kv.a. capacity, and when the load on this bank was exceeded a second bank was put into service in a temporary position, and the steelwork for it in its permanent position was erected lastyear. Hamilton No. 2.-- This substation, as well as Arapuni, Penrose, and Bombay, will be a point of transformation from 110 kv. to 50 kv., and for that purpose a 10,000 kv.a. bank of transformers (3 single-phase and 1 spare) is being installed, together with the necessary steelwork and switchgear, including 110 kv. potential transformers and 110 kv. line protective equipment. Wcdimo.—Two boosting-transformers for boosting the 11 kv. voltage were installed and are adjusted so that the synchronous condenser can automatically maintain constant voltage. New protective equipment was installed on the two line 0.C.8.'5. Takapuna— The new 2,250 kv.a. transformer-bank, steel structure, and bus-work was completed and put into service. Kerepeehi, Waihou, Matamata.—A new 50 kv. line 0.C.8. and new_sokv. line-protective equipment were installed and put into service at each of these three substations. 4. Operation and Maintenance. (a) Power-stations. Ara/puni (Generators, 60,000 kw. capacity ; transformers, 11/110 kv. 72,000 kv.a., and 110/50 kv. 12 000 kv a.).—After completion of repairs to the headrace, and of work in the overflow-channel and falls, a start was made to fill the lake on the 24th March, and water flowed over the spillway on the 6th April, 1932. Nos. 1, 2, and 3 units were started up on the 3rd April, and, after the necessary drying-out, the station took load again on the 10th April. Maintenance work during the year was as follows : — Turbines : A considerable amount of erosion was found on the runner-blades and shroud ring of Nos. 2 and 3 units, caused by cavitation. The governor drive-gears have given a good deal of trouble during the year. Arrangements are being made to substitute electrical drive for this gear drive. Under conditions of varying load and varying vacuum in the draft-tube it was found that in the water-catcher over the labyrinth there was sometimes pressure and sometimes a partial vacuum. Pressure tended to force water into the oil-catcher, and vacuum tended to draw oil down the drafttube. A great improvement was made by providing vents (1 in. holes) in the water-catcher, so that the interior would always be at atmospheric pressure, thus preventing both of the above troubles. Alterations were found necessary to the roller thrust bearings of the auxiliary units. Generators : The leads from the exciter and to the generator field were originally taken through a pipe through the thrust-bearing housing, and a very slight leak of oil into this pipe caused the insulation on these leads to perish. The leads were replaced with new leads, taken up outside the bearing housing. To minimize suction of oil down around the shaft above the rotor, air-hole vents were drilled below the upper oil-catcher on No. 1 unit.

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