HYDRO-ELECTRIC SUPPLY.

Shannon News, 27 May 1927, Page 4

HYDRO-ELECTRIC SUPPLY.

THE MANGAHAO SCHEME. Some particulars of a great " ■ SYSTEM. An interesting description of hydroelectric .work in New'Zealand, with special reference to the Mangahao scheme, was given at a gathering of the Levin Chamber of Commerce Lunch Club, in the Oxford Tea romps on Friday, by Mr I. R. Robinson, chief electrical engineer at Mangahao. Rev. J. D. McArthur presided, and said he was pleased to welcome Messrs J; W. Rimmer, C. Blenkhorn, P, H. Harper, K. E. Adams and G. L. Adkin. Apologies for absence were received from Messrs J. W. Gibson, P. W. Goldsmith, J. 1 W. Bishop, C. 11. Martin, J. A. ' McQueen, and F. H. Hudson. The chairman extended a hearty welcome to Mr. Robinson, and said that his remarks should be followed with great interest. At the outset Mr. Robinson said the electric scheme was a very big one, and he would attempt not to weary his hearers with technical details. In New Zealand the Government had taken up the work of electrical power development and had laid out a scheme for the whole of the North Island. There was a plan to inter-connect the big power stations for mutual assistance. The Government put up the new power houses and transmission lines; they, then sold the power to the Power Boards, who retailed it to the consumers. This system, so far as he knew, was unique in the world, as in other countries companies were interested in the distribution of electric current. The system adopted by our Government had suited New Zealand conditions best, and the smaller townships and country places had been reticulated in a manner which had not been surpassed elsewhere in the world. The Mangahao River flowed on the I- eastern side of the ranges; and to develop the scheme two dams and tunnels were built in the hills above Shanfibn, with a surge chamber to compensate for changes of load. There were 'five pipes entering the power house. Each of the three large pipes supplied an 8000 h.p. generator, and each of the two smaller pipes a 4000 h.p. generator, providing in all 32,000 horse-power. The Mangahao was a very ‘(flashy” river—it was subject to very sudden and big floods. It was intended to put in a third dam, up the river, to provide additional storage. The load already was greater than it was intended to be when the station should be fully developed; and the position was analogous to that of an engineer who had laid out a water-supply for a town of 16,000, to find that the population had suddenly risen to 20,000. At the present rate of growth of . the load it looked as if they would have, to call on the other hydro-electric systems for assistance. The generators produced 11,000 volts.. This was the voltage supplied to the Horowhenua Power Board; but most of the current was transformed from 11,000 to 110,000 volts. For the Wellington load two lines were carried on wooden poles as far as Paekakariki, and from there they were carried on steel towers to the; Khandallah substation. There were two lines : to Bunnythorpe, another to Wanganui, and another over the Ruahines to Woodville sub-station, which was a, switching station. l>ne line went north from Woodville to Napier, and another went south to Masterton. The power at Khandallah was broken down from 110,000 to 11,000 volts, and was, supplied to • various large users, such as the City Corporation and the Railway Department; and at the other substations supplies were sent out through various power boards. The total length of 110,000-volt 'lines was 352' miles; 1054 miles of cable were used, and there were 4400 poles, 150 steels towers, and 93,000 insulators. The Department had its own independent telephone lines running to Masterton,. Bunnythorpe, Wanganui, and down to Khandallah. By means of this service the staff at the power house and the sub-stations were kept informed of faults, and information was received two or three times a day as to the weather over this large area. In the power-house t,here were three men on duty all the time—one attending to the switchboard, one running the machines, and the third man greasing and cleaning. In addition there were" the power-house superintendent and the chief engineer; they did not take a shift, but attended to repairs

and; inspection, and acted as executive officers 5 on that section. In all about IS men were required to operate the power house. At Khandallah there were six men, including the superintendent.- At each cf the . other sub-stations there were two men, whose.duties were to attend to the sub-stations, answer telephones, and carry out repairs on th<? lines if required. Two or three linesmen were' at the power station to look after that section of line. There was one. engineer at the power-house for lines, and another at Dannevirke. In addition there was the clerical staff, and another engineer for general administration. The head-quarters of the system at present were at Shannon. The station had a huge amount of stores, and five or six people were employed for handling them.' At each sub-station there was a car or lorry for quick mea.ns of transport in ease of break-downs. 'Altogether the system had 31 motor vehicles, and with such a large fleet there were always some repairs to be done. Mr. Robinson added that the Mangahao scheme had had to encounter a considerable number of troubles. This was the first system at 110,000 volts to operate in New Zealand. There were certain devices put on the transmission lines for the purpose of cutting off the current, in the event of troubles occurring. These used to cut out the lines when it was not desired; but the staff had now got over that trouble. From Woodville to Norsewood was tbe windiest . section of country he knew of. On the wooden poles, in addition to three power-lines, there was a fourth line as a guard against lightning. This lighter wire used to be blown against the heaviey lines. One day a workman saw a severe ' flash, , indicating the cause of the trouble; and as a result of the discovery it was possible to take steps to remedy it. Lightning did not cause any serious damage in this country; but at Onge Onge a good deal of expense was incurred when the substation had been , burnt through this cause. As the result of the visit of an engineer lent by the Canadian Government, it was now possible to test the insulators on the lines, so that any bad ones could be removed before the line broke down.

Other troubles experienced by the Department had been due to the growth of the load. Instruments were only effective for measuring a certain range of load. To the end of March, 1926, the capital outlay on the system was £2,022,000. Of that amount £520,000 represented capital that was not in operation —for example . that spent on the upper dam. The revenue for the year was £76,859; the working expenses, £21,865; and balance, £54,993, available for capital charges, such as interest. The systejn actually earned 3.65 per cent, on the capital in operation, which was not a bad achievement. Actually they showed a loss in the balance-sheets, because under the law each; of the schemes had to earn 5.4 per cent, interest on all the money invested. They had also to put away 2 per cent, for depreciation reserve. During the past year the revenue had been very much more than in the. previous year. A very dry summer had been experienced, and without’the services of the third dam, the position was an unfortunate one, as they had to pay a considerable amount to purchase power from the Wellington City Corporation, the Rangitikei Power Board, and 'the

Palmerston North Borough. In the initial stages of the scheme, each of the Boards was asked to guarantee a certain load. Practically all of them had greatly exceeded that guarantee. For the year just ended, the Horowhenua Board guaranteed to take £5200 worth of current; but actually they paid for £14,000 .worth. There were other Boards which had paid for twice as much current as they had guaranteed to take. The difficulty was that, while the growth of the load had been so quick, the Department, had not yet been able to get the third dam built, and the load was going to be bigger than the system was devised to take. In reply to a question as to whether Waikaremoana would be able to make Up any deficiency in the Mangahao system, Mr. Robinson stated that the local system was installed with a 32,000 capacity and Waikaremoana would have have an initial installation of 40,000, and the latter could be extended and more ower obtained very easily and cheaply. Asked who was going to serve Taranaki with electricity, Mr. Robinson said that this was “in the lap of the gods” at present. The President of the Chamber (Mr. ■ T. F. Gibson) said that it was some-’ what surprising to learn the extent of country alrea’dy covered by the Mangahao electric scheme, and those present were much indebted to Mr. Robinson for his interesting and instructive address.