92 BELL SYSTEM TECHNICAL JOURNAL 



2. A reasonable degree of balance of the loads between the three 



phases of the power circuit. In the higher- voltage rural 

 circuits this also includes the lengths of branches consisting 

 of one or two phase wires and neutral. 



3. The avoidance of unnecessarily heavily loaded branches consist- 



ing of one or two phase wires and neutral. 



4. The prevention of excessive over-excitation of transformers. 



5. The grounding, where necessary, of aerial telephone cables at 



or near both ends of an exposure to obtain the benefits of 

 magnetic shielding. 



6. The use of adequately coordinated telephone transpositions on 



open-wire extensions and the avoidance of severe unbalances 

 in the open-wire conductors. 



7. The correction of badly distorted voltage or current wave shape 



on the power system. 



8. The connection of the neutral point of three-phase wye-delta 



load banks to the system neutral conductor. 



9. The use of telephone station apparatus, on party-line service, of 



lower susceptiveness. 

 10. Occasionally the use of arrangements or apparatus to minimize 

 the effects from unbalances in central office equipment. 



It is, of course, essential in successfully coordinating the power 

 distribution and telephone circuits that, as in other coordination 

 situations, the power and telephone people view the matter as a mutual 

 responsibility and fully cooperate in the application of the tools 

 available. Experience over a period of years has now shown that 

 where this is done adequate overall coordination can be readily 

 secured. ^^ 



The authors wish to acknowledge their indebtedness to their many 

 coworkers who aided in carrying on the various investigations on which 

 this paper is based. 



Bibliography 



1. "Improvement in Distribution Methods," S. B. Hood — p. 1038 of 1925 Trans. 



A.I.E.E. 



2. "Interconnection of Primary Lightning Arrester Ground and the Grounded 



Neutral of the Secondary Main," C. F. Harding and C. S. Sprague — p. 234 of 

 1932 Trans. A.I.E.E. 



3. "Lightning Protection for Distribution Transformers," K. B. McEachron and L. 



Saxon— p. 239 of 1932 Trans. A.I.E.E. 



4. "Lightning Protection for Distribution Transformers," A. M. Opsahl, A. S. 



Brooks and R. N. Southgate— p. 245 of 1932 Trans. A.I.E.E. 



5. "Studies of Lightning Protection on 4000-volt Circuits — III," D. W. Roper — p. 



252 of 1932 Trans. A.I.E.E. 



6. "Lightning Protection for Distribution Transformers," T. H. Haines & C. A. 



Corney— p. 259 of 1932 Trans. A.I.E.E. 



