D.—l

88

General. The operation of the whole system throughout the year has been satisfactory, many of the difficulties of the earlier years of operation having been overcome. With the growth of load on the system, particularly since the inception of operation of the Waikaremoana Station, the purchase of additional equipment at substations becomes necessary, and at the present time additional oil circuit-breakers are being installed at Napier, Waipukurau, Dannevirke, Woodville, and Bunnythorpe Substations. Again good results have been obtained with the buzz-stick method of testing insulators on live lines, and the third series of tests is now nearing completion. Linesmen have been brought to the power-house for a " refresher " course in this work immediately prior to the commencement of the annual tests on the lines. The results of tests this year confirm those obtained in previous years, two makes of insulator standing out as much better than other makes at present in use. Apart from the testing of insulators, on only two occasions has it been necessary to work on transmission-lines under live-line conditions. At pole 177, near Ashhurst, a parallel-groove clamp was tightened, and on the Dannevirke-Waipukurau section a cotter-pin was replaced in a tie-down clamp while the line was still in service. Trouble is still occasionally experienced with A.C.S.R. cable, broken strands resulting from vibration. Between power - house and Bunnythorpe eight broken strands have been detected, all being in the spans adjacent to the Manawatu River crossing. Repairs have been effected and investigation made as to means of overcoming this trouble. Similar trouble has been experienced in other parts of the world, and various types of damping-devices have been tried, some with marked success. Similar devices will be tried on our lines during the coming year. Tail-race. —Additional groynes have been built in the tail-race, existing groynes extended, and fascining carried out at many places. The tail-race is now in good order, and protective works are standing up well. Design Work. During the year the electrical design office prepared plans and issued drawings for the staff dining-room and for the single men's quarters in connection with Mangaore Village Settlement. With the advent of power from Waikaremoana it became necessary to prepare fresh layout plans and drawings in connection with Napier, Waipukurau, Dannevirke, Woodville, and Bunnythorpe Substations, to provide for the additional steelwork and switch-gear. Construction. Khandallah Substation. —'During the year erection of the 10,000 kv.a. synchronous condenser and its control equipment was completed, and this plant is now operating satisfactorily as required. A current-limiting resistance has been installed in connection with the 250 kv. testing transformer. Earth-leakage and definite time-limit relays have been fitted to the Petone Railway and the Wellington Meat Export Co.'s feeder panels, and put into service. New printometers have been installed and tested, and are now operating satisfactorily. New ironclad switch-gear has been erected for the control of additional feeders to Wellington City and put into service. Bunnythorpe Substation. —The 110 kv. oil circuit-breaker used as a tie-switch has been re-erected on a steel framework, which permits switch-tanks to be lowered for inspection of contacts when required. New 0.C.8.s have been purchased for this station, and have recently come to hand. Their erection will be put in hand during the coming year. Meantime the necessary concrete foundations have been put down. Wanganui Substation. —A well has been sunk in the substation grounds for a permanent watersupply for the station and cottages. New leakage-relays have been installed on the main 11 kv. switch. Marton Siibstation. —Erection of this station is now proceeding to give a second point of supply to the Wanganui-Rangitikei Power Board. This Board closed down its steam plant as from the 31st March, 1929, and now takes the whole of its supply from the Department. A 1,500 kv.a. transformer has been transferred from Dannevirke and installed at Marton on a concrete foundation. A four-pole structure has been erected and an air-break switch assembled thereon. The necessary 11 kv. switch-gear and metering equipment is on order, but until it comes to hand a temporary supply will be given without metering equipment. Woodville Switching-station. —The garage and workshop, which were destroyed by fire, have been rebuilt, and a shelter-fence has been erected round the cottages. A new 0.C.8. has been purchased for this station, and has recently come to hand. Erection of same will be put in hand at an early date. Mangamaire Substation.- —A 1,500 kv.a. synchronous condenser and the necessary control gear have been erected at this station, and are operating satisfactorily as required. A battery-house has been erected and 110-volt battery installed for supply to condenser and 0.C.8. controls. The solenoid coils on the 0.C.8.s have been changed for 110-volt supply. A battery-charging motor-generator set has been installed in conjunction with the new battery. A spare 1,500 kv.a. transformer has been purchased for this station, and has been dried out ready for service when required. Owing to the high voltage at Mangamaire when Waikaremoana is supplying power to the system, it has been necessary to install an auto-transformer to reduce the L.T. voltage to a normal value. A 2,200-gallon outdoor oil-storage tank has been installed and oil-piping connected thereto.