TABLE III 103 



For single-phase lines use 2 R and 2 X in place of R and 

 Xj and use >2 F in place of Y 



(14) Allowance for Extra Impedance. 



Only a very slight error is introduced, for practical 

 power-transmission lines, by adding the resistance and 

 reactance of the transformers and protective reactance 

 coils, referred to high tension, to the line resistance and 

 reactance, when convergent series are used as in the pre- 

 ceding paragraphs. The exact solution would involve 

 treating the impedances at the ends as separate sections 

 of the line, each section to be calculated by itself. This 

 method is long, and does not lend itself to the direct 

 solution of the problems considered above. Such ex- 

 actness of calculation also would not seem to be re- 

 quired for the usual accuracy of engineering problems 

 in connection with power transmission. 



