ELEMENTS OF A TRANSMISSION LINE 5 



and it has an important bearing on the electrical charac- 

 teristics of the line. 



An alternating magnetic field is formed around, and in- 

 side of, conductors carrying alternating currents. This 

 field generates a voltage along the conductors which is 

 proportional to the current, like the voltage drop due to 

 resistance, but which is 90 out of phase with the current. 

 This voltage is called the reactance drop. Tables of re- 

 actance of transmission lines will be found in Part III. 



Since the voltage drop in a transmission line is due to 

 resistance and reactance, a simple line may be considered 

 to be made up of the elements shown in Fig. i. If R is 



Reactance 



' ffece/y- 

 E er or 

 Reactance Load. 



qnfflHRnnp *- 



Fig. i. 



the total resistance, the voltage drop in phase with the 

 current / will be IR, and if X is the total reactance, the 

 voltage drop in quad- 

 rature with the current 

 will be IX. 



The vector diagram of 

 the above quantities will 

 be as in Fig. 2. The cur- 

 rent is in general not in 

 phase with the voltage Flg * 2> 



E, but lags behind it by an angle 6, according to the 

 power factor, cos 0, of the load. The resistance drop IR 

 will therefore not be added directly to , but must be 

 added vectorially, along with the reactance drop IX, as in 



