﻿caused by a Break in an Overhead Wire. 201 



W being the weight of the half span. Differentiating the 

 last equation and using the first, 



dT __ dc _ ds _ dc _ dT 



T ~ C s ~ c X ' 



Differentiate the equation 



. . x 

 s=csinn -, 



and put for e/,s and dc their valnes in terms of cZT. We arrive 

 at the equation 





orra 



Writing/ as before for ' ., ., we have 

 increase of tension /■' 



. _ ^r •' -t ' gj|y 



increase of horizontal span „ 2/# ' J ' 



1+ x 



If the constant f is replaced by this decreased value, the 

 remainder of the analysis holds. 



Taking the actual numerical values used before, viz., six 

 wires each weighing '42 lb. to a foot, tension of each 1000 lbs. 

 and span 100 yards, we found for / for the whole set, the 

 value 1 5120. Assume for X the value 2*8 x 10° (for one wire) 

 and we find 



/ ,s =ToJt= 1190 °- 



In arriving at this value of X for 000 wire we use the figures 

 given for 00 wire by Mr. A. P. Trotter (' Electrical Times/ 

 10th May, 1906). 



The modified values of the constants a and b are 



a= 2~27 instead of 2*21, 

 b= -50 „ 0-40. 



The maximum deflexion caused by breakage of all the 

 wires in a bay works out to *752 feet instead of the former 

 value '696 feet ; i. <?., a difference of about finch in the per- 

 missible deflexion of the top of the pole. 



