60 ELECTRICAL EQUIPMENT 



potential will be the sum of the incoming and reflected waves, 

 while the current will be represented by the difference of the two 

 waves since they travel in opposite direction. If we thus denote 

 the voltage and current of the reflected wave by e 2 and i 2 and of 

 the transmitted wave by ei and ii, we get the following relation 

 at the transition point. 



but 



fc-; 



The amplitude of the transmitted voltage wave is, therefore, 



2Z 2 



and of the reflected voltage wave 



JL 



Similarly we get for the current 



2Z 2 . 



/l j 



Zi+Z 2 

 and 



If, therefore, Z% has a higher value than Z\, it follows that the 

 voltage of the traveling wave is transmitted to the second circuit 

 at an increased amplitude and vice versa. A traveling wave 

 originating in an underground cable will, therefore, enter an over- 

 head circuit with an increase in voltage, while a wave originating 

 in an overhead circuit will pass into a cable system with a lower 

 voltage. 



These relations between the reflected and transmitted waves to 

 the incoming wave are, however, only applicable to cases where 



