

WORKING METHODS OF CALCULATION 83 



them, the efficiency, power-factor, etc., can be directly 

 calculated. 



Although the term Y for the admittance of the line 

 may include the conductance between wires due to insu- 

 lator leakage and corona loss, it is not usual to include 

 the effect of leakage and corona when calculating the 

 line characteristics, but to take Y as equal to only the 

 capacity susceptance. The reason for this is that insu- 

 lator leakage under ordinary conditions is generally 

 negligible compared with other line losses, and corona 

 loss ought to be quite negligible under normal conditions. 

 When corona loss once starts, it increases at a very rapid 

 rate as the voltage goes up. If corona loss is at all ap- 

 preciable under normal conditions, then the energy loss 

 during unfavorable weather conditions of any kind be- 

 comes very serious. Accordingly, it has been found best 

 to operate lines well below their corona point. For this 

 reason Table V has been inserted. This was published 

 in The General Electric Review of December, 1912, by 

 Mr. F. W. Peek, Jr., who has made the most authori- 

 tative determination of the laws of corona loss of trans- 

 mission lines. From this table, the voltage may be 

 found at which corona loss begins to be appreciable for 

 any given line under normal conditions; it is generally 

 not desirable to operate above these voltages. 



Example I 



Find the line efficiency, the generator P. F., and the 

 reactive Kva. required from synchronous phase modi- 

 fiers, for the four-mile, constant-voltage line, Example 

 IV, Chapter X. 



