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National Resources Planning Board 



them of very comprehensive importance. All the more 

 important of these, and many of the lesser companies, 

 carry on organized research, and important proportions 

 of their products are formed on the results of the 

 research. Many such concerns add to the range of 

 their own research by cooperating with university 

 laboratories or with special research institutions. 



Ever since John Hopkinson, some 50 years ago, 

 published the rational theory of the magnetization 

 cm'vo of the complex magnetic circuit of a dynamo, 

 designers and inventors have struggled by experimental 

 and mathematical research to find means for reducing 

 the various losses, reducing the weight, reducing the 

 bulk, and reducing the cost of electrical generators and 

 motors per unit of output, and for improving their 

 reliability. The features involved have related to 

 ferrous metallurgy; the qualities of insulating materials; 

 problems of heat flow and heat transfer for cooling 

 purposes; problems of air resistance; problems of 

 lubrication; problems of welding versus casting of 

 frames; problems of stamping, slotting, and securing 

 disks; and various other matters affecting the structure 

 of such machines and the materials entering into them, 

 besides the problems of adapting the machines to the 

 service needs of users. The improvement of the 

 product has been gradual and its extent is not fully 

 realized by present-day users; but comparisons of 

 generators and motors available 30 years ago with the 

 present-day product show results that notably justify 

 the intense work of innumerable able men and the 

 large research expenditiu^es. Space does not afford 

 opportunity here to examine the matter in detail, but 

 the fact stands forth that our present reliance on 

 electric power as a national resource rests strongly on 

 the improvements arising from this continuous re- 

 search. Further research promises to disclose still 

 further advantages. 



Equally intensive and continuous research has char- 

 acterized the field of circuits for the transmission and 

 distribution of the electric power and the equipment 

 associated with such circuits. Transmission voltages 

 have been raised and reliability improved by researches 

 in the field of insulation for both overhead and under- 

 ground lines. Reliability of transmission has been 

 secured by applying the residts of research relative to 

 transforming and switching devices, and the difficulties 

 relating to "stability" for power systems have been 

 greatly diminished by similarly intensive research. The 

 safety of circuits for the distribution of the electric 

 power on the premises of customers has been similarly 

 established. The present voltage considered the upper 

 limit for alternating-current power-transmission circuits 

 has not far exceeded 220,000 volts. It is, however, 

 contemplated using 287,000 volts on the lines from 

 Boulder Dam to Los Angeles. What research may 



accomplish in raising this for the purpose of mcrcasing 

 the economical distance over which power may be 

 transmitted, and what may be accomplished with 

 high-voltage direct currents, have not yet been disclosed 

 by the researches now under way. 



Methods of testing machines and circuits in situ have 

 been developed; and coordination of insulation is 

 studied for the purpose of improving reliability of the 

 power systems, which associates with studies for improv- 

 ing the details of the system structures. The preven- 

 tion of harmful effects of traveling electromagnetic 

 waves on high-voltage circuits has received adequate 

 attention, as have the problems of the most efficient 

 distribution of incremental loads between generators 

 and circuits. Many featm-es of the physical strength of 

 circuits and associated devices have required extended 

 research. The problems of corona caused by electronic 

 discharge between conductors have been grappled with 

 for the purpose of preventing deleterious effect on insula- 

 tors and insulating materials and avoiding excessive 

 power waste on transmission lines. Metallurgical and 

 mechanical problems relating to the electrical conduc- 

 tivity and the mechanical strength of the materials 

 available for line conductors have received their propor- 

 tion of research attention. Even the prevention of 

 vibration of costly conductors erected in long spans, 

 which vibration causes breakage from fatigue stresses, 

 has called for attention by men familiar with the theories 

 of vibrations and with vibration phenomena. 



Intense lightning effects are characteristic of many 

 zones in this country, and are natural to a greater or 

 less degree in most parts. These have been the cause of 

 much damage to high-voltage electric-power systems 

 and of interruptions to service. Elaborate researches 

 in the field of lightning phenomena, the characteristics 

 of lightning, and means for preventing damage to 

 electric systems by lightning strokes have enlarged, and 

 are still enlarging, our knowledge of these matters with 

 the result that lightning protection of power systems is 

 reasonably complete. 



Insulated electric cables for high-voltage power 

 systems are so important a factor that this subject is 

 here assigned the next section for itself. 



Insulated Electric Cables for 



Power Transmission and Distribution 



The increasing voltage needed for the delivery of 

 great bulks of power from urban power stations, and the 

 reluctance of city governments to permit heavy circuits 

 for high- voltage power to be established overhead in the 

 streets, brought the problems of underground cables 

 very much to the foreground. This imposed a major 

 problem of research on the cable manufacturers and the 

 power companies, which is related to the conductors and 

 their mutual arrangements; the insidating materials. 



