MUTUAL IMPEDANCES OF GROUND-RETURN CIRCUITS 631 



current in the disturbing line, the open circuit induced voltage in each 

 of the short ground-return circuits, and the phase angle between these 

 two quantities were measured. The mutual impedances were derived 

 from the ratio of the induced voltage to the inducing current, in ac- 

 cordance with the definition. The results of these tests are given on 

 Figs. 2, 3, and 4. Fig. 2 shows the resistance components, Fig. 3 the 

 reactance components, and Fig. 4 the magnitudes of the mutual im- 

 pedances. 



0.7 



0.5 

 0.4 



0.3 



^- 0.2 



UJ 

 UJ 



u. 



o 



o 



S 0,1 



Q. 

 W 



2 0.07 



I 

 O 



O 0.04 



z 



< 



3 0.03 

 a. 



2 



< 



H 

 =) 

 2 



0.02 



0.01 



0.007 



0.005 



20 30 50 100 200 300 500 



HORIZONTAL SEPARATION IN FEET 



Fig. 4 — Cross Keys tests — mutual impedance. 



1000 



The measurements described above were made with the object of 

 investigating the mutual impedances of ground-return circuits in which 

 the ground connections on the disturbing line are sufficiently removed 

 from those on the disturbed circuit so that effects due to proximity of the 

 grounds may be ignored. The results presented above were supple- 

 mented by observations demonstrating that the induced voltage in a 



