ELECTRICITY SUPPLY

Evening Post, Volume CIII, Issue 46, 24 February 1922, Page 7

ELECTRICITY SUPPLY

SOME PROBLEMS DISCUSSED

DOMESTIC COOKING AND STAND-

BY PLANTS.

Some interesting aspects of the problem of electricity supply were discusses! by Mr. F. Black, M.1.E.E., in a paper read at the annual meeting of the Society of Civil Engineers. Sir. Black endorsed the policy or establishing full stand-by plants, and made a plea for the encouragement of domestic cooking by electricity. A main essential to success in electricity supply, he said, was to secure a combined demand of the greatest possible diversity of application. Although not liiuch could be done to control or alter the inherent diversity value of the various classes of demand, a great deal could be accomplished in improving the load-line by some effort directed towards educating the potential consumer in new fields.

"An important class of demand,' which in this country is more backward than in some other parts of the world, is that of domestic cooking," said Mr. Black. "Having a diversity value of about 7 and gifing an almost entirely daytime load with its maximum value hear, or at rioon, it is capable of considerably improving outputs from generating plants the size of which have been based on power and lighting demands. The v desirability of encouraging adoption of electric cooking— not merely for the odds and ends of culinary work, but for the main operations— is not sufficiently recognised, in the writer's opinion, even by some supply engineers. The reason for this is probably that the apparatus required by the consumer has been, and to some extent still is, iindergoing a process of evolution. There are now manufactured, however, quite a number of kitchen outfits which are proving both reliable and economical in hard service.

SECONDARY POSITION OF

LIGHTING.

■"We have passed the stage when domestic supply meant only lighting, and undertakings must recognise that reticulations designed for a lighting business cannot serve indefinitely in a wider sphere. As the cooking demand does not come on. the evenings peak, it is entitled to the same charging rates as power, and will then .yield an average revenue of from £15 to £20' per equipped house per annum, of, roughly, five times the revenue from tie lighting. There is some reason, therefore, for a substantial investment in mains over and above what is required for lighting supply. The foregoing classes of demand* are those which there is every reason to believe will within the next few'years form the main business, of public electricity supply. Lighting is already in a secondary position, and is fast being rendered, in comparison, quite a minor activity by the growth of the various power and heating demands. The loadline in the past has always improved as defnand widened, and in large cities, at any rate, it will yet become such as to largely, reduce the disparity in the total cost of production at different periods in the 24 hours."-

CONTINUITY OF SUPPLY.

Discussing the important question of maintaining continuity of supply, Mr. Black stated that in ono sense the main-. tenance of. a continuoun supply of electrioity by an undertaking might not be regarded as related to demand. That was to say, the employment of certain means to that-end was a matter not necessarily affected in a technical way "by the' use being made of current by the consumer. In a wider view, however, there was a relationship of importance. Every year saw the undertaking in any district assuming greater responsibilities to the community. As time went on almost every activity of city life and a number ixi rural areas would be dependent in greater or less degree' upon electricity supply from some undertaking, if only the service given was reliable and maintained a good standard of continuity. The days of the isolated, purely local undertaking were commencing to pass away in several countries; it would be one of the tasks in the new order of things to reach as excellent a record in that respect as most of those undertak--1 ing's possessed. The demand of the hear future would represent such widespread interest that failitre of supply, even for brief periods, could only be described as pulling up suddenly and then holding helpless an entire community. In the sense, therefore, that relianc* on Continuity of supply should be well founded as an essential to the full development of demand, the two matters had an intimate connection. . ■

FULL STAND-BY^ PLANTS.

It was a feature of all long-distance transmission systems (whether the energy comes from water or fuel) that interruptions were more frequent and complete, and gave, less warning of their imminence* than was the case with well designed and maintained local undertakings; The latter had developed a means <jf protecting their consumers—duplicate and sectiohalised 'bus bars, duplicate circuit breakers, ring mains, split mains, and so on—but the former were seldom able to do anything to safeguard their vulnerable part, the Tine, other than by adopting a good class of construction, which, while in itself important, did not give immunity against breakdowns. Duplicate lines, whether on common poles or along separate routes, were fery costly, and gave only partial protection. As long distance transmission was becoming more and moro employed, for the connecting up of individual undertakings, the position being reached was that the safeguards against interruption of supply (apart from the use of the best type of plant) could only consist of: First, the supply of current from one generating source to.any other linked to it (when the link is not involved in the trouble); and, second, local stand-by plant;- Mr. Black expressed the opinion that in New Zealand, owing to the wide separation of the few cities and the sparsely populated nature of the country, the comparatively limited number of main transmission lines would not in the majority of instances be suitable for linking up. Here and there a few suitable instances might be found, but no general linking-up in each of the two islands would be commercially practicable Or technically useful until-such time as the country war much more closely settled and carrying a greater inland population than at present. In a word, successful linking-up was a matter of breadth as well as length. In Mr. Black's opinion fuel stand-by plants in the more important of the towns were indicated as the method most generally suitable for the country's condition. It would be outside the scope of the paper to discuss the nature of those, but it might be pointed out that so long as peak loads of any magnitude remain a feature of supply, stand-by plants will have a second use of great financial importance, inasmuch as they will be employed to reduce the maximum demands of the local load upon the .main supply.