INDUCTIVE COORDINATION 93 



7. "Distribution System Lightning Studies by Philadelphia Electric Company," 



H. A. Dambly, H. N. Ekvall, and H. S. Phelps— p. 265 of 1932 Trans. A.I.E.E. 



8. Engineering Reports 6, 9, 13 and 15 — Vols. I and II of Engineering Reports of 



Joint Subcommittee on Development and Research of National Electric Light 

 Association and Bell Telephone System. 



9. Common-Neutral Practice Confirmed in California — p. 980 — ^June 4, 1932 issue 



of Electrical World — (See also May 15, 1932 issue of Electrical West.) 



10. Provisional Report No. 18 of Joint Subcommittee on Development and Research 



of Edison Electrical Institute and Bell Telephone System. 



11. "Measurement of Telephone Noise and Power Wave Shape," J. M. Barstow, P. 



W. Blye and H. E. Kent— p. 1307 of 1935 Trans. A.I.E.E. 



12. Reports of Joint General Committee of National Electric Light Association and 



Bell Telephone Systems on Physical Relations between Electrical Supply and 

 Signal Systems — Edition of Dec. 9, 1922. 



Appendix 



For the sake of brevity, the detailed calculations and some of the 

 minor assumptions for the following examples have been omitted. 



Illustrative Example 1 



The purpose of this example is to show, for average power 

 system wave shapes: 



1. The noise induction problem that might be created by the 



exposure of a reasonably long aerial telephone cable 

 in an urban area with a heavily loaded single-phase 

 feeder. It features: 



a. The relative importance of triple and non-triple har- 



monic induction, and 



b. The extent to which planning of routes, grounding of 



cable sheaths, etc. might improve the situation. 



2. The changes in the noise magnitudes for the same situation 



with the various single-phase loads well distributed 

 among all three phases. Under this condition, 

 attention is directed to: 



a. The change in the relative importance of the triple and 



non-triple harmonic induction. 



b. The amount of reduction obtained by the same remedial 



measures tried in \-b above. 



Figure 3 shows a possible method of supplying the single-phase loads 

 •n a rather extensive part of an urban area. The general layout shown 

 on Fig. 3 is such that all of the current for the feeder area traverses a 

 considerable part of the exposure. Under this quite extreme condition 

 — essentially single-phase supply for a relatively large area — the noise 

 at location C under heavy load conditions would be about as shown on 

 Table I. 



