Pacific service magazine . isreached and costs begin to increase due tothe fact that the cost of losses increasesmore rapidly than the cost of fixed chargesdecreases. For a typical 110 kv. line 50miles in length the minimum cost is reachedat 45,000 kw. per circuit. {See Fig. 5 onfollowing page). This determination of minimum cost issimply an application of Kelvins law. Inusing this law the cost curve should bedrawn rather than solving the equation forthe minimum because the curve is oftenquite flat near the minimum. Not infre-quently large savings of first cost are pos-sible with a small incre
Pacific service magazine . isreached and costs begin to increase due tothe fact that the cost of losses increasesmore rapidly than the cost of fixed chargesdecreases. For a typical 110 kv. line 50miles in length the minimum cost is reachedat 45,000 kw. per circuit. {See Fig. 5 onfollowing page). This determination of minimum cost issimply an application of Kelvins law. Inusing this law the cost curve should bedrawn rather than solving the equation forthe minimum because the curve is oftenquite flat near the minimum. Not infre-quently large savings of first cost are pos-sible with a small increase in annual engineer must realize that the rais-ing of funds for a project is quite as mucha problem as are the technical problems andthat a slightly higher operating cost is oftento be preferred to very high fixed a given transmission line it may bebetter to increase the load beyond the eco-nomical point than to incur the large ex-penditure of capital for a second line. Pacific Service Magazine 293. *0 60 80 100 120 THOUSANDS OF KILOWATTS PER CIRCUIT Operation The problems of operation must be con-sidered in the design of a transmission sys-tem. Aside from isolated cases of directcurrent^ supply in the business districts oflarge cities protected by storage batteries,electrical energy must be generated, trans-mitted and distributed continuously and inprecisely the amounts required by the cus-tomers. No other business is quite so ex-acting. Water may be stored in reservoirs eventhough the distributing pipes should alwaysbe full. Gas may be stored in holders suf-ficient for several hours supply. Electric-ity must be generated as used. Additionalgenerators must be brought up to the exactspeed and voltage of the system before theymay be synchronized. Absolute continuity of service is impos-sible on any high voltage transmission failures may occur due to light-ning or other causes. Testing, cleaningand ultimate replacement of insulators isneces
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