CABLE TESTING 683 



Two balancings are necessary, as indicated in Fig. 426. 

 From the first balancing, 



M Z + y 



N ' x 



From the second balancing, 



N' " x + y 

 Then 



.! 



(12) 



If a slide wire or its equivalent is used for the balance arms, 



M + N = M' + N f and 



x = (x + </) J (12a) 



When the resistance per unit length of conductor is uniform, 



f W* + i 



distance to fault = [ -^ | X (length of cable) (13) 



F + 1 



Corrections for Conductors of Different Diameters. -In the 



foregoing it has been assumed that the resistance per unit length 

 of cable is uniform. In some cases, however, the conductor may 

 be made up of a number of wires in series which have different 



U 



\ 



A 



" 



FIG. 427. Pertaining to the location of a ground in a non-uniform 



conductor. 



diameters. The lengths and sizes of the wires in the different 

 sections will be known from the office records. Let the lengths 

 be I, h I, . and let the corresponding resistances per u 



length be X,>* K,, . . . The resistances of the sections will 

 be as indicated in Fig. 427. 



