D—4

NELSON-MARLBOROUGH SECTION A. SYSTEM OPERATION AND LOAD DESPATCH 1. Load The maximum half-hourly demand on the system was 13,907 kW. on 16th June, .at 1730 hours. This was 10-5 per cent, higher than the previous year's peak of 12,586 kW. The increase in the units generated was 14-6 per cent. The maximum number of units generated in any one week was 1,600,241 for the week ended 19th June, 1949 (last year 1,394,769). The system annual load factor was 61 per cent. Units generated (compared with those for the previous year) were as follows :

Auxiliary and standby stations— Waihopai .. .. .. 1,883,417 2,749,936 Other miscellaneous .. .. 4,380,829 2 002,296 Total units generated and purchased 74,456,046 64,990,832 The units generated by the auxiliary and standby stations represent 8-3 per cent, ■of the total, compared with 7-3 per cent, during the previous year. 2. Eeliability op Supply A complete blockage of all turbine spears by rocks and gravel occurred at Cobb Power-station during the peak period on 19th May. As stones were thought to be in the pipe-line load was limited to 11,000 kW. until Sunday, 12th June, when the station was taken out of service for 11 hours to enable a screen to be fitted in the stone-trap. On 17th December the station was shut down for 18 hours 28 minutes, commencing at 2302 hours to change over from the old intake to the new. The following table gives a detailed analysis of faults. Pre-arranged shutdowns .are not included.

29

Year Ended 31st March, 1950. Year Ended 31st March, 1949. Station. Maximum Kilowatts. Unit? Generated. | I Annual Load 1 Factor. Maximum Kilowatts. Units Generated. Annual Load Factor. 'Cobb 12,900 68,191,800 Per Cent. 60 j 11,920 60,238,600 Per Cent. 58

i Y ear | Year Ended 31st March, 1950. Ended Description. | 31st March, Number. Duration. 1949. 1. 66 kV. lines : Defects 1 h. 0 m. 03 2. 66 kV. lines : External causes •• 1 0 25 3. 11 kV. lines : Defects 2 4 03 4. 11 kV. lines : External causes 2 3 7 15 5. Lightning 4 6. Storms 7. 6-6 kV. apparatus 8. 11 kV. or 33 kV. apparatus 4 1 0 38 9. 66 kV. apparatus 1 •*- 1 0 07 10. Turbines 3 2 40 11. Relays .. . . .. j [ 4 12. Control circuits and batteries 1 o' 39 13. Operation : Mistakes 14. Operation : Accidents 15. Faults and overloads on consumers' systems 15 3 0 48 16. Other causes 1 o 02 17. Causes unknown 3 4 0 24 Totals .. .. .. | 33 21 1 17 04