432 SUBMAKINE CABLE LAYING AND REPAIRING. 



the steps in its solution in order that those using the test may 

 easily follow the reasoning. 



The following example will show the manner of working out 

 the test : — 



Ohmic balance not necessary to record. 



Cable charge D = (198 x 100) = 19,800 



Line mid break resistance R = 11,500 ohms 

 Condenser charge f^=(265xl0)= 2,650 



The numbers 100 and 10 are multiplying powers of shunts 

 used for the throws D and cl respectively. 

 The other known data were — 



K (Condenser capacity) = 20 mfds. 

 r (Cable CR per naut)==3 ohms 

 Jc (Cable capacity per naut) = 0'34 mfd. 



By (7) L=^ ^ '' 



Q d ' K ■ l 



19,800x20x2x3 ^ ^^ 



ni =0"2o 



2,650x11,500x0-34 



By (9) w = l- Vi-0-23 = 0-1225 



By (10) Distance of break = 11,500x0-1225 = 1,410 units. 



It is important that the cable CK and capacity per naut 

 should be as exact as possible. Breaks are generally in shoal 

 water, where the temperature is comparatively high and there- 

 fore if there is a deep water section it is not quite correct to 

 take the mean CR or capacity per naut of the whole cable. 

 When the appoximate position of the break has been found a 

 temperature correction for the CR per naut can generally be 

 made where records of the sea temperature for the summer and 

 winter seasons are available. Also if it is known from the 

 Splice List that in this particular locality the capacity per naut 

 is different from the mean over the whole line, this value should 

 be used in the formula. In short, every care should be taken 



r 

 that the ratio t is set down as accurately as it can be ascer- 

 tained in respect of the section of cable up to the break. 



The latest revision of this test has been publisted in the 

 Electrical Eeview of July 24 and 31, and Aug. 7 and 14, 



