D—4

2. Reliability of Supply There has been a total of 236 faults, of which 229 caused interruptions to supply. Included in this total are 24 secondary interruptions caused by faults in consumers* systems. A detailed analysis of interruptions is shown on the following table. These do not include prearranged shutdowns :

B. OPERATION AND MAINTENANCE 1. Power-stations All the generating-plant at the main stations was run satisfactorily and there were no major breakdowns. The loading of each station required constant and careful consideration in anticipation of high peak loads expected during the winter of 1947. The storage of water soon became a matter of major, and then of vital, importance. The increase in the number of units purchased from 216,481 in 1946 to 5,869,146 in 1947 gives ample evidence that steps were taken early to counteract any shortage of water. Of the 5,869,146 units purchased, 4,617,752 were generated by auxiliary stations operated by steam power. Coleridge.—The lake-level, which stood at 1,673*2 ft. at Ist April, 1946, declined to 1,665-67 ft. at 23rd July. Wet weather then set in and recovery was rapid. The lake was again full at the beginning of March. The continued lack of north-west rain and heavy demands on the station due to Highbank being shut down and Waitaki and Arnold outputs reduced resulted, however, in a rapid fall to 1,669*82 ft. at 31st March, 1947. The rainfall for the year 1946 was 35*16 in. For the first time in at least forty years a snowfall of 2 in. was recorded as lying at the power-house in February. A general overhaul of Nos. 1, 2, 7, and 8 units was carried out. No. 3 was repaired following the breakage of three guide vanes; the shaft alignment was tested, and middle bearing moved slightly, there being, however, little reduction

21

Year ending 31st March, 1947. Description. Distributing Number. Duration. Authorities affected. h. m. 1. 110 kV. lines : Defects 2 7 52 10 2. 110 kV. lines : External causes 3 1 58£ 7 3. 66 kV. lines : Defects 8 2 15 1 4. 66 kV. lines : External causes 1 0 08 5. 11 kV. lines : Defects 69 52 22\ 3 6. 11 kV. lines : External causes 41 19 36£ 2 7. Lightning .. .. .. .. 30 62 42 7 8. Storms : Nature of trouble unknown 8 10 01 3 9. 110 kV. equipment 2 2 02 1 10. 66 kV. equipment 3 4 57 3 11. 33 kV., 11 kV., or 6-6 kV. equipment 4 3 44£ 12. Generators 13. Turbines i 0 01 2 14. Diesel-oil engines 15. Relays 16. Control circuits and batteries i 23 35 17. Operation: Mistakes I 0 06 9 18. Operation: Accidents 6 0 56£ 9 19. Faults and overloads on consumers' system 24 29 12 4 20. Other causes 8 4 44£ 8 21. Cause unknown 24 14 58£ 5 Totals 236 1 241 12i 74