D.—l.

A detailed survey of the Maungatapere-Kaikohe section was carried out, and a general route was selected for the line from Kaikohe to Kaitaia. Horahora-Hamilton 50 kV. Line. —A deviation to avoid the aerodrome at Rukuhia was completed in December. Ongarue-Taumarunui 11 kV. Line. —Pole sites were pegged and material ordered, but construction work has not yet commenced. Hamilton-Frankton 11 kV. Line. —A deviation was made at Nortons Road in December to suit the Department of Housing Construction. (2) Operation and Maintenance. (a) POWER-STATIONS. Arapuni.—A total interruption to 110 kV. supply occurred in April, when a workman made accidental contact with a 110 kV. lead at the outdoor station. Two 11 kV. bus faults were caused by rats, one in August, which tripped out No. 1 generator, and the other in October, which tripped out No. 2 generator, but station supply was not interrupted. Owing to low river-level the whole of the river flow was taken by the turbines during certain periods in October. Horahora.—New chains and pins were fitted to the sealing-pipes, and six new rollers were fitted to the roller-trains on the non-automatic gate in the weir. Penrose Diesels. —The plant was given a short maintenance run each week. (6) SUBSTATIONS. Penrose. —To enable the existing transformers of the 22/50 kV. bank to be interchangeable with the new transformers, the 22 kV. cable boxes attached to the bushings on the old transformers were removed, and the cables were terminated on a new cable structure adjacent to the 22 kV. bushings. New 22 kV. and 50 kV. leads and new Merz Price bushing type C.T.'s were fitted to the transformers. Two 110 kV. bushings were replaced, on account of causing excessive radio interference. Bombay. —An 11 kV. C.T. on a Power Board feeder 0.C.8. broke down in August, and a 50 kV. bushing on the Kerepeehi line 0.0.8. broke down in January. The tap-changing switch on one of the 50/11 kV. transformers was damaged in December by arcing caused by a defective contact. Hamilton. —Two 11 kV. C.T. failures occurred in January. Two more failures occurred in February, and another in March. The old C.T.'s were replaced by tested C.T.'s from stock, and an undamaged but corroded coil was submitted to the Dominion Analyst for examination. It was found that the corrosion was due to nitric acid formed by the hydrolysis of nitrocellulose in the varnish used on the coil by the manufacturers, the action being accelerated by the warm, humid conditions which prevailed at the time of the C.T. failures. Henderson. —Four defective 50 kV. insulators were replaced. Tahekeroa.—A 1,000 kVA. 3-phase transformer was transferred from Huntly in February for use as a spare. Mareretu. —A temporary 11 kV. local service transformer was damaged by lightning in May, and flashovers on a 50 kV. transformer bushing and a 50 kV. insulator were caused by lightning in September. Maungatapere. —The 50/11 kV. transformer bank was livened on 15th July to give supply to a local service transformer during construction. Supply was not required by the Power Board until 26th September. Kerepeehi.—Two 11 kV. C.T. failures occurred on a Power Board feeder 0.C.8., one in June and the other in November. Lightning caused a flashover in the 11 kV. sealing bell of one of the 50/11 kV. transformers in February, but no material damage was done. Waikino. —-An 11 kV. C.T. broke down in November, and Power Board supply was interrupted by a rat on the 11 kV. bus in March. Waihou. —An 11 kV. single core, outdoor cable-box on the incoming feeder broke down in November, and a flashover was caused in December by the cap of an insulator on a 50 kY. A.B.S. breaking off when the switch was opened. Matamata.—An 11 kV. C.T. failure occurred on a Power Board feeder 0.C.8. in June. Te Awamutu.—A 50 kV. bushing broke down in January and damaged three other bushings. Hangatiki.—A cracked 50 kV. transformer bushing was replaced. Ngongotaha.—Three cracked 50 kV. bushings were replaced. Rotoiti. —The 100 kVA. 47-5/6-6 kV. transformer broke down during a thunderstorm on 17th February. A spare transformer was installed, and new coils were ordered for the damaged transformer. Edgecumbe and Waiotahi. —The 11 kV. earthing reactors, which were taken out of service when the 750 kVA. transformer banks were replaced by 1,500 kVA. banks from Hamilton, are being reconditioned in readiness for service at Ngongotaha. Huntly, Takapuna and 11 kV. Substations.—No trouble was experienced at any of these substations. General.—New forty-hour-week rosters were adopted for substation operators in January. This has necessitated the provision of additional quarters for relieving operators at twelve substations. (c) TRANSMISSION AND DISTRIBUTION LINES. (i) 110 kV. Arapuni-Penrose.—No trouble was experienced on either the wood-pole or tower-line circuits. The work of removing the earth wire from the wood-pole line was carried out as opportunity permitted, but the work is not yet completed. Earthing points were installed at seventeen poles.

84