D—4

B. OPERATION AND MAINTENANCE 1. Power-stations Cobb.—The peak load carried by the Cobb generators was 12,900 kW. at 1200 hours on 15th June. To reduce the possibility of flood damage the level of Lake Halley was lowered at various periods. During February and March water storage fell. Pumping water from Lake Sylvester with a jet-pump commenced on 27th March, which added another 960 kW. to Cobb Station. The rainfall was 74-17 in., compared with 76-64 in. for 1948-49. The spears, nozzles, and turbine buckets of all machines were repaired, and the main valves were also overhauled.

Machine-running Times

Stoke Diesel Station. —The Diesel house was extended and four Diesel-operated alternators of 360 kW. capacity (continuous) were installed and commenced operation on 11th March. The station generated 979,700 units, which was 580 per cent, of last year's generation. The machine-running times were : No. 1 machine, 508 hours ; No. 2 machine, 674 hours ; No. 3 machine, 516 hours ; No. 4 machine, 355 hours ; No. 5 machine, 499 hours ; No. 6 machine, 379 hours. 2. Substations 66 kV. All Buchholz relays were replaced at Blenheim and Motupipi owing to oil leaks in the castings. The Nelson City Council cable-box on the terminal structure at Stoke failed on 19th October. 3. Transmission and Distribution (a) 66 kV. Two poles struck by lightning on the Upper Takaka - Motupipi line were replaced(b) 11 kV. The Motupipi—Tarakohe line was deviated for approximately one mile at the Tarakohe end to allow the Grolden Bay Cement Co. to extend its quarry. 4. Communications Faults were mostly due to high winds, and branches falling on the line in the bush areas. Daily radio communication was used between Nelson, Cobb, and Lake Sylvester for lake-levels during the dry period and to arrange supplies during lake-control work. 5. Testing New apparatus was tested and usual routine duties carried out. 6. Plant and Motor-vehicles Transport relies on a fleet of vehicles most of which are over ten years old and have seen hard service in both the Department and the Army. During the year two 15 cwt... one 18 cwt., and one 3-ton chassis were received for work on transmission-line construction. Two cars were received, one of which was a replacement.

30

Generator. Time on Load. Time Idle. Time Under Repair. Percentage Availability for Service. Hours. Percentage. Hours. | Percentage. . Not in Demand (Hours). In Demand (Hours). 1 7,442 85-0 1,183 13-5 115 20 98-5 2 7,436 84-8 1,213 13-8 91 19 98-7 3 .! 7,513 85-8 1,079 12-3 152 15 98-1 4 7,495 85-6 1,167 13-3 76 21 98-9