ELECTRIC POWER

Evening Post, Volume CXII, Issue 135, 4 December 1926, Page 7

ELECTRIC POWER

FULL VOLTAGE IMPORTANT

DROP MEANS SHORT MEASURE

LETTER TO SUPPLY AUTHORITIES,

An interesting circular, addressed to the officials of public electrical supply undertakings in New Zealand, has been issued by the Chief Electrical Engineer, Public Works Department. It states:—

"With the.increasing number of electric lighting, cooking, and heating installations throughout the Dominion, the question of correct voltage of supply is becoming more important. ... In some cases the results of electric service are not always, satisfactory from the consumer's point of view. This can be attributed very largely to excessive voltage drop on distribution lines, or the inadequate size of wires installed on the premies causing too great a voltage drop between the supply systeni and the appartus in use.

"Electric lighting and heating appliances are particularly sensitive to low voltage, and if the distribution lines or interior wiring, as the case may be, are inadequate, the popularity and universal use of electricity for these purposes are likely to oe seriously jeopardised. Every current consuming appliance on the market to-day, whether it be an incandescent lamp, motor, range, or water heater, is designed to give its maximum efficiency at a specified voltage, and variation beyond the recognised voltage limits interferes with the efficient operation of the appliance. LIGHTWEIGHT GOODS. "A tradesman or firm selling any commodity which is 'light weight' incurs the penalty1 of the law for defrauding the customer, and low voltage can be deemed to be in the same category as 'light weight' goods. The consumer is paying for electrical supply at a specified voltage, and this supply should be up to the required standard. The 'quality" is directly dependent upon voltage regulation, and electrical energy loses its value as a commpdicy when variations in voltage exceed certain limits. These limits are already well know to every electric supply authority.

"In connection with the effect of voltage variation on incandescent lamps it can be shown that if the voltage drops 11 per cent., a 50 c.p. lamp will only give as. much light as a 32 c.p. lamp with its full rated voltage, and, furthermore, the 50 c.p. lamp will consume 27 per cent, more power thali the 32 c.p. lamp for the same amount of illumination. As regards the effects of low voltage on heating apparatus such as ranges, hot water systems, radiators, etc., the power consumption does not vary directly as the applied voltage, but as the square of the applied voltage, and the outstanding result of this makes itself very evident in the longer time taken to perform cooking duty. Curves have been prepared to co-ordinate the relationship between voltage variation and time taken in cooking, and these show the following results: — /

5 per cent, decrease in voltage increases the heating time by 10 per cent, and period of cooking by 12 per cent. 10 per cent, decrease in voltage increases the heating time by 25 per cent, and period of cooking by 30 per cent. 20. per cent, decrease in voltage increases the heating time by 55 per cent, and period of cooking by 70 per cent.

"As an example, consider the case o£ a 1500 watt element in a stove and the normal cooking time as 30 minutes. The energy consumption at full voltage would be 750 watt hours. AVith voltage 10 per; cent, low, the time is correspondingly increased to 39 minutes, and the energy consumption 789 watt hoursj which is clearly a case of the, consumer being illegally charged for extra energy due to the supply authority's voltage being below standard. PREJUDICE AGAINST THE ELECTRIC RANGE. "I wish to stress this factor of low voltage, especially where cooking apparatus is installed, as this helps to .explain prejudice that exists against the 'electric range as'compared with its gas competitor in length of time required for -cooking;. The old objection to the use of the electric range for cooking, namely, the time taken even at normal voltage, has been overcome by the adoption o£ high wattage elements, and consumers must be supplied at correct voltage if the maximum of satisfaction is to be atained by both suplier and usev. High voltage is also detrimental to electric supply, but its prevalence is not so great as to require more than this passing reference to.its effects. "The existing conditions as regards voltage of supply on consumers' premises appear to warrant some investigation, as instances are suspected wher.e low voltage is being supplied and it is felt that some licensees are not fully alive to this phase of the electric supply business.

"One of the fundamental conditions of all licenses is that a satisfactory supply must be given to consumers, and in the interests of electric supply in general, it is desired that supply authorities make it a practice to look carefully into the question of the suitability of the 'wiring on premises before connecting up heating loads, and if complaints are being received from consumers already wired up, it \% hoped that they will promptly ascertain and remove the cause.

"This Department is anxious to cooperate with all electric supply authorities in providing a commodity which will be in popular demand. . . . Increased demand most assuredly follows if a supply is maintained which fulfils1 its obligations, and this ultimately leads to a cheapening of the cost of electricity which is the aim of all those interested- in providing same.