Page:Harnessing the Waihopai.pdf/10

Page Eight switchgear, 25 feet higher, this arrangement being necessary to keep them well above flood level. Portion of the floor space is allocated for office and telephone equipment, and adjacent to this is a space for carrying out minor repairs. Overhead, and running the full length of the building, is a Morris 4-ton traversing crane, supplied by Messrs. A. D. Riley & Co.

One result of the building of the dam is to create a lake of about 70 acres in extent, and, in order to beautify this, and at the same time provide the Board with poles and other necessary timber, the surrounding country has been acquired and is being planted with suitable trees.

In the construction of the headworks, but not including the road works, it has been necessary to excavate some 24,000 tons of earth and rock, and mix and place some 12,000 tons of reinforced concrete, requiring some 1600 tons of cement and 120 tons of steel.

So far as materials and plant are concerned, it has been the aim of the Board to utilise Now Zealand and British products to the fullest extent.

The power plant consists of two vertical shaft Gordon turbines, of the Francis type, with spiral easing (supplied by Messrs. John Chambers & Son), each driving a 500 k.w. 6600 volt generator, supplied by the British General Electric Company, Britain. The generators are raised some 22 feet above the turbines, so as to be protected from floods, the river in the neighborhood of the power house being in a narrow gorge and subject to a rise in level of some 25 feet during periods of high flood.

The switchgear is of the latest totally-enclosed armoued type, supplied by Messrs. Reyrolle, Ltd., Britain, and is designed to give the utmost safety and relinbility in the operation of the power units, and to control the supply to the transformer station, and to the local country feeder.

In designing the plant, provision has been made to shut down the generating sets automatically should any of the usual contingencies arise, such as the heating of bearings, shortage of water, over-speed or under-speed, or any electrical fault. The station will, therefore, be capable of running without continuous attendance, and will be the largest power station in New Zealand to be so arranged.

Special arrangements have been made to provide for the testing of the machinery and protective devices at any time without in any way affecting the supply to the Board’s area. The station is arranged so as to be readily extended and a third or fourth unit installed, should such be warranted by the increase in load.

The transformer station, which is of the outdoor type, is erected immediately above the power house, and has a capacity of from 1200 te 1500 k.w., with a stand-by transformer unit, and is used to step up the voltage from 6600 to 33,000 volts for transmission to Renwicktown, Blenheim, Seddon, and, at a later date, to Havelock and Picton. The transformers are of Ferranti make, supplied by Messrs. A. D. Riley & Co., Ltd., and the switchgear and lightning and other protective apparatus of G.E. make, supplied by the National Electrical and Engineering Co., Ltd.

The transformer station, as well as the sub-stations at Renwicktown, Blenheim, and Seddon, is built of steel designed and fabricated in New Zealand. Provision is made in all cases for inereasing the capacity of the station.

The main transmission line, from Waihopai to Blenheim, has a length of 23 miles, and is constructed for operation at 33,000 volts. The cable consists of steel-cored aluminium, supplied by the Northern Aluminium Company, Canada, through Messrs. Richardson, McCabe, & Co., and is carried on Ohio brass insulators, supplied by Messrs. Carrick, Wedderspoon, & Co. Ltd. The transmission line to Blenheim is carried on galvanised steel towers, supplied by the Canadian Bridge Company, Canada, through Messrs. Dansey & Company, Auckland, and is capable of transmitting some 4000 horse-power.

At the Renwicktown sub-station provision is made for the future extension of the transmission system, at 33,000 volts, to Havelock. From Blenheim the 33,000 volts transmission line continues on 40-foot concrete poles, to a switching tower erected on Vickerman Road, at which point the linee will branch northwards to Picton, and also to Seddon in the South.

The Seddon line is to be erected principally on 40-foot concrrte poles, with 101-foot sterl towers at the crossing over the Opawa River, to allow for navigation of same. The hilly seetion over the Redwood Pass will also be traversed on steel towers, to avoid the difficulties in transport and erection of concrrte poles on the steep hillsides.

The transmission line wires to Seddon will consist of No. 6 Copperweld, a conductor with a copper welded to a steel core; and the line is designed to carry a heavier conductor should it be required in the future owing to the éxtensive growth of load in the Awatere district and beyond.

At Renwicktown the principal country sub-station is located of a capacity of 375 k.w., with a stand-by provision. The transformers, which were supplied by Messrs. A. D. Riley & Co. hore break down the voltage to 11,000 volts for the supply of the reticulation system to Havelock, Mahakipawa, and Tua Marina.

At Blenheim the principal city sub-station is located, of a capacity of 750 k.w., with a stand-by provision.

The 33,000-v. apparatus in the case of both sub-stations is of G.E. make, supplied by the National Electrical and Engineering Company, Ltd., and the 11,000 or 6600 volt switchgear of Ferguson & Pailin make, supplied by Messrs. A. D. Riley & Co.

The sub-station at Seddon will be a duplicate of that at Renwiektown, and will have provision for a load of 375 k.w.

The reticulation system, so far, is designed to consist of three main zones—the Wairau-Havelock-Tua Marina area, supplied from Renwicktown at 11000 volts; the Blenheim area, including Blenheim and suburbs, supplied from Blenheim at 6600 volts ; and the Southern area, including Ward, Awatere, and the adjacent districts, supplied from Seddon at 11,000 volts. The lines throughout are being erected on concrete poles, made