LIGHT FOR STRATFORD.

Taranaki Daily News, Volume LVII, Issue 289, 15 May 1915, Page 3

LIGHT FOR STRATFORD.

PROPOSED MUNICIPAL ELECTRIC SUPPLY. EXGIXEKR3' REPORT. At a recent mooting of the Stratford Borough Council the question of entering upon municipal enterprise in the matter of the electric light supply was discussed, and it was decided to request Messrs 11. W. Cliniie and Son, engineers, to report upon the most suitable standardised plant for generating electrical energy to suit the Stratford borough requirements and an estimate of the cost of the same The report received deals only with an entirely new installation, independent of existing operations.

Referring to the motive power, the report says:- —We consider that a prime mover with a normal output of 200 horse-power would meet the requirements of your district for some time. Two units each of this power, however, should be installed, and provision made in the station building for installing a third set of the same power as soon as the demand exceeds the overload capacity of one of them. Continuity of supply would then be independent of a break-down in any of the generating sets.

Oil fuel could he used to greatest advantage in Diesel engines. The only water-powers worth considering within practicable distance of your town are those on the Patea river. We have carefully investigated several of the most promising, and find that the best is that occurring in the four miles of rapids above the Mangaehu stream, where a fall of some RT feet can to obtained. Although the volume of water is considerably increased by the Mangaehu stream, the water-powers below the junction are neither so great nor so easily developed. The main feature in the development of this water-power would he a tunnel some 56 chains long through the hills from the intake to the'turbines installed in a power-house about half-a-mile bc'ow the Mangaehu stream. From measurements of the flow made higher up the river in one of your recent dry seasons we estimate that a minimum flow at the proposed in-take of not less than 70 cubic feet per second could be ridied on. This amount of water under the fall available would produce some 540 brake-horse-power, equivalent to 500 horsepower if generated in the town, or ton timc3 more than derivable from the company's present water-power station in j dry seasons. This amount of power we > consider would be ample for many years, and if ever necessary it could be considerably increased by building ;) storage . reservoir, which at the same tin'? would : increase the fall. We think that the ) development of this power should he I seriously considered. The power station would, in a direct line, be some 0y 2 > miles from town, though about 13 miles I by the. route the transmission line would I have to take. This would probably be I via the Robson, Bird, Skinner and War- I wicK roads, and across country where found desirable. The relative merits of water, steam and Diesel engines as a ' motive power should be determined not of course by their initial cost, but from considerations as to the annual charges required to meet operating expenses, interest and depreciation. The annual charges would be at least on the waterpower, and most on the steam plant, though (luring the first years of the undertaking (when the annual output would be about 150,000 units) the difference in favor of water power over Diesel engines would not be great. The cost of fuel and the more skilled attention required for the Diesel plant more than counter-balances the heavier capital charges on the water-power scheme. The steam power station would be burdened with heavier interest charges on the greater capital sunk in larger station buildings, smoke stack, etc. The choice of a motor power therefore lies between water-power and Diesel engines. The annual saving in favor of the hydro-elec-tric scheme will increase with the annual demand, and this consideration outweighs) we think, any objections that can be raised against it. The revenue derived will certainly not be less.

COST OF THE SCHEME. Regarding tlie electrical system, the engineers point out that an alternating current system wonM have to be installed and that the three-phase system Would be the cheapest and best to adopt, with a frequency of oO cycles -per second. In the hydro-electric scheme current should be generated at 3300 volts, stepped up to 11,0U0 volts for transmission and then stepped down in a sub-station in the town to 3300 volts for distribution in the borough.

l'"or distribution the town should be divided into several areas and each fed by a separate high-tension circuit, supplying a number of pole transformers in each area with three-phase current at 3300 volts. 'From the transformers lowtension would be distributed on the four-

wire three-phase system at 230 vo'ts for lighting and 400 volts for power. As the outside edge of 'practically all footpaths on both sides of the streets are already occupied by other overhead lines, it will lie necessary to place the new poles along the fence line and adopt a side-arm construction. This method of supporting the lines could not be carried out in the business area, so it would be necessary to carry the cables underground in Broadway from Celia to Seyton streets. The extra expense of this construction over that usually adopted, we estimate will be £I2OO. The street lighting can be most efficiently carried out by supplying the lamps with low-tension current supplied

from three single-phase transformers, each fed by a separate high-tension circuit controlled from the sub-station. The number of lights supplied by each transformer should be approximately equal. We suggest that before your Council definitely decide on a change of voltage all private installations be re-tested and the number required to be improved or replaced determined. We estimate it would not cost more than £SCO for the Council to replace all lamps and heating apparatus connected to 'private installations. The actual number of candle-power, etc., could be determined at the same time as the house wiring is being re-tested. Unless much of the wiring i s faulty, and provided the present house service meters are not acquired, we estimate there would be a saving at the present time of about .tIOOO by changing over to 230 volts, with increasing economy with every extension to the distributing system. ' Throughout the wliole undertaking we have estimated for work of a substantial nature. The station buildings and substation would be of ferro-concrete, and

office accommodation for manager and clerical stair has been included. The estimated total capital cost of the various schemes arc:— Hydro-electric scheme, £32,140; with extra (third) generating set, an additional £4B(io. Expense of replacing all apparatus connected with present company's mains, £I2OO. Diesel engine scheme, £23,440; third generating set, £3850. Steam engine scheme, £28,346; third' generating set, £sllO. Replacing ap-, paratus connected with 'present com-' pany's mains, £I2OO. The estimated annual charges on generating and transmission system are: — For an output of 150,000 units 'per annum Hydro - electric plant, £2002; Diesel engine plant, £2757; steam engine plant, £3125. For an output of 200,000 units per annum plant, .C 2682; Diesel engine plant, £21)08; steam engine plant, £3270. For an'output of 300,000 units per annum Hydro-electric plant £3277; Diesel engine plant £3743; steam engine plant, £4253. Management, operating expenses and capital charges on the distribution system, common to all schemes, are not included in these figures.