D—£

2. Reliability of Supply There was a total of 232 faults. Of these, 4 were general system outages for periods of up to 10, 17, 14, and 23 minutes respectively, affecting a majority of consumers. The duration given refers generally to the period of outage of the line or equipment concerned ; the periods of interruption to consumers were usually shorter.

The following analysis does not include prearranged shutdowns.

B. OPERATION AND MAINTENANCE 1. Power-stations There were no serious defects or failures of permanent equipment. Two interruptions to supply from Waitaki were caused by failure of switchgear temporarily in service during alterations. Below average rainfalls were experienced until June. Rainfalls for the whole year were below those of the previous year. Coleridge.—Owing to prolonged dry weather, and in particular the absence of north-west rain, the lake-level fell rapidly from 1,669-82 ft. at 31st March to 1,662-45 ft. on 7th June. Rationing of power and subsequent wet weather retrieved the position. The lake was filled to overflow level (1,673-5 ft.) by 9th November, remained full until the middle of February, and stood at 1,671-07 ft. at the 31st March, 1948. Comprehensive overhauls of Nos. 2 and 3 generating-units were carried out, the work done including the welding of cavitated runners and the fitting of new sets of fabricated guide-vanes. A general overhaul of No. 4 unit was completed.

21

Year ending 31st March, 1948. Year ending Description. 31st March, 1947. Distributing Number. Duration. Authorities affected. 1 h. m. 1. 110 kV. lines : Defects 2 8 38 15 20' 2. 110 kV. lines : External causes .. 3 7 1 17 7 3. 66 kV. lines : Defects 8 27 19 00 84. 66 kV. lines : External causes 1 8 18 48 165. 11 kV. lines : Defects 69 74 45 56 3i 6. 11 kV. lines : External causes 41 38 27 22 T 7. Lightning 30 9 5 05 8. 8. Storms : Nature of trouble unknown 8 18 12 38 1 9. 110 kV. equipment 2 5 25 53 5 10. 66 kV. equipment 11. 33 kV., 11 kV., or 6-6 kV. equipment 3 8 45 & 4 9 6 51 1 12. Generators 13. Turbines i 14. Diesel-oil engines 15. Relays 16. Control circuits and batteries i , . 17. Operation: Mistakes I 0 40 5 18. Operation: Accidents 6 19. Faults and overloads on consumers' system 24 2 0 35 1 20. Other causes 8 21. Cause unknown 24 17 721 *3 Totals 236 232 218 26 90