I)— 4

2. Reliability of Supply Although 242 faults were experienced, there was only one general interruption to the whole system when a bird caused a fLashover on the Waitaki-Glenavy 110 kV. line. Some faults caused disturbances or interruptions to one or more supply authorities, but the periods of interruption to consumers were generally shorter than the period of outage of the line or equipment concerned. The following analysis does not include prearranged shutdowns :

B. OPERATION AND MAINTENANCE 1. Power Stations Coleridge.—The year's rainfall was 42-4 in. at the Harper and 27-53 in. at the powerhouse (previous year 47-01 and 36-07 in.). The lake reached overflow level, 1673*5 ft. in August and J'anuary, but was reduced to 1670-38 ft. on 31st March, 1950. A new record maximum half-hourly demand of 43,380 kW. was recorded from. 11.30 a.m. to noon on 27th June, 1949. This was an overload of 25-7 per cent, on the station rated capacity of 34,500 kW. At the Harper intake, further extensive groyne work was carried out. Steel plates were laid on the intake gate spillways to provide a more permanent surface and reduce maintenance. Major overhauls were carried out on Nos. 1, 2, 3, 7, and 9 generating-units, and reconditioning of valves was effected on Nos. 4 and 6.

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Year Ended 31st March, 1950. Year Ended Description. 31st March, 1949. Number. Duration. h. m. 1. 110 kV. lines : Defects 2 1 4 06 2. 110 kV. lines : External causes.. 5 8 2 38 3. 66 kV. and 33 kV. lines : Defects 12 12 8 14 4. 66 kV. and 33 kV. lines : External causes 8 4 7 14 5. 11 kV. lines : Defects* 79 72 75 18. 6. 11 kV. lines : External causes* 42 34 25 00 7. Lightning 8. Storms : Nature of trouble not found* 7 14 10 47 22 36 51 369. 110 kV. equipment .. .. 1 4 9 44 10. 66 kV. and 33 kY. equipment 8 10 5 56. 11. 33 kV., 11 kV., or 6-6 kV. equipment 20 10 15 41 12. Generators 1 13. Turbines 14. Fires : Scrub 1 1 01 15. Relays 1 0 07 16. Control circuits and batteries 1 1 12: 17. Operation : Mistakes 5 1 0 07 18. Operation : Accidents . . 3 0 07' 19. Faults and overloads on consumers' system 2 6 1 37 20. ■ Other causes 4 0 24 21. Causes unknown* 8 20 16 09 Totals 222' 242 236 58 1 * Includes Southland Electric-power Supply retail distribution.