INDUCTIVE COORDINATION 91 



In rural areas where both distribution services must ordinarily be 

 carried along the highways the opportunity for controlling the coupling 

 between the two classes of circuits by cooperative planning of routes is 

 much reduced. 



Some benefit may be gained, however, in the case of open-wire 

 construction particularly at joint-use separations, by arrangements of 

 the conductors on the pole so as to avoid excessive spacings. As 

 shown on Fig. 2 certain arrangements tend to minimize the amount of 

 noise induction arising from the power circuit voltages and currents. 

 This beneficial effect is, however, much less noticeable at roadway 

 separations. 



Summary and Conclusions 



Since about 1915 there has been a continued increase in the use of 

 the multi-grounded or common-neutral arrangement of power distri- 

 bution in this country. At the present time, approximately half of the 

 distribution is by 4000-volt multi-grounded or common-neutral cir- 

 cuits. A large part of the higher-voltage rural distribution is also 

 operating with this arrangement. 



In general it may be said that for the lower-voltage 2300/4000-volt 

 distribution circuits, the use of the multi-grounded or common-neutral 

 arrangement may be expected to increase the inductive influence of 

 the power circuits. Unless attention is given to cooperative planning 

 to secure features beneficial from the inductive coordination stand- 

 point, noise problems may result either in restricted or extensive areas. 

 With proper attention to the coordination features ^ such noise situa- 

 tions as develop are largely in the nature of isolated cases and can 

 usually be cared for by relatively minor changes or adjustments in 

 either or both plants. 



For the higher voltage (11-13 kv.) rural distribution circuits, there 

 seems to be little difference, from the noise induction standpoint, 

 between the uni-grounded four-wire system and the multi-grounded or 

 common-neutral arrangement. ^° Under many conditions the placing 

 of multiple grounds on the neutral will result in noise reductions due 

 to the effect, previously mentioned, of the multi-grounded neutral on 

 the line charging currents. It is interesting to note that experience 

 to date with the multi-grounded or common-neutral in rural areas has 

 shown that many of the measures of coordination applicable in urban 

 areas will prove similarly helpful in rural communities. 



The measures of coordination which investigations and operating 

 experience have shown to be practicable and effective include: 



1. Cooperative planning by both parties to avoid not only severe 

 exposure conditions but also types of equipment likely to 

 aggravate the possible noise induction situation. 



