D—4

Maximum load on generators for year, 21,000 kW ; load factor, 62. Extensive repairs to the concrete apron of the tail : race outside the power-station were carried out. The generator-running times were as follows :

2. Substations At most substations the operators were required to work a large amount of overtime on load-restriction switching. Where possible, automatic devices were installed to overcome this. Some unusual operating-conditions occurred causing outages when excess current was exported northward through Bunnythorpe from Waikaremoana. Regular inspection of, and minor maintenance to, all apparatus was carriedoourt r and, in addition, progress was made with the systematic periodical overhaul of transformers and bushings. A critical examination of substation earthing-systems, where these have been exposed, has shown that, in general, the bolted connections are unsatisfactory, and as occasion offers the systems are being redesigned. Maintenance to buildings has been done as found necessary. {a) 110 IV. Penrose. —The jumpers on lines 3 and 4 were removed, and No. 3 now functions as a separate line. The installation of distance impedance relay protection on all incoming transmission-lines was completed. The new control-room was brought into full use. Following recommendations by the Fire Inspector, additional fire-fighting equipment has been installed. RosJcill. —A complete new 110 v. control battery was installed. The installation of non-bouncing contacts in transfer switches and new selector-switch arm assemblies was completed. Lightning caused breakdown between turns on two adjacent transformer units, and these units also flashed over externally, the fault being cleared by relays with very little and easily repaired damage. Henderson. —The shop work for the modernization of the 110 kV. control-board is well under way. The dust-proofing of the switch-room was completed. Lightning caused a flashover across contacts on the 110 kV. off-load tapping-switches in two adjacent units in the 30,000 kV. bank, the fault being cleared by the simultaneous opening of a line 0.C.8. The relays gave the alarm, but did not trip due to a fault in the tripping circuits. Hamilton. —An outage of a 110/50 kV. transformer bank was caused on Ist May, 1946, by a breakdown of the pyrotenax cable in the relay circuit, and two outages of another 110/50 kV. bank were caused on 4th January, 1947, and 6th January, 1947, by water in a junction-box of the pyrotenax cable. Ongarue.—A 110 kV. fuse at Ongarue gave trouble on 4th September, 1946, following which all three fuses were removed. Waihou was changed over to 110 kV. supply on 6th March, 1947. Masterton. —New metering C.T.s were fitted.

10

Generator No. Time on Load. Time Idle. Time under Repair. Percentage Availability for Service. Hours. Percentage. Hours. Percentage. Not in Demand (Hours). In Demand (Hours). 1 8,236 94-0 471 5-4 53 99-4 2 8,273 94-4 429 4-9 25 33 99-3 3 8,298 94-7 417 4-6 40 5 99-5 4 8,315 94-9 414 4-7 31 99-6 5 8,157 93-1 421 4-8 93 89 97-9