480 



ELECTRICAL EQUIPMENT 



current in any part of the sytsem can be read by means of an 

 ammeter. 



For a more complete description of this calculating table, the 

 reader is referred to the " General Electric Review " for October, 

 1916. 



Fig. 297 shows a complicated network in which a number of 

 generators feed a common bus at points separated by bus-bar 



A ^K Kv-a. 



-* 111,000 Kv-a. 



tlll.OOO 

 Kv-a. 



10* 



301,000 

 Kv-a. 



8.1* 



192,000 

 Kv-a. 



VW, 

 ATA 1 



-* 23,000 Kv-a. 



^nr?r&> 



o 



1 104,000 

 Kv-a. 



3-7,000 K\ 



TSlfSir^- 



260,000 

 Kv-a. 



3.W 



116,000 

 Kv-a. 



52,000 Kv-a. 



'145,000 



O 



14.1!? 



157,000 

 Kv-a. 



> 13,000 Kv-a. 



O 



20.7 



18,000 

 Kv-a. 



6,000 



* 



83,000 



6 Kv ' a ' 



FIG. 297. Short-circuit Current Calculations. 



reactors. The percentages of reactance given are based on 45,000 

 Kv.A. The short-circuit occurs at the point A. The solution of 

 this problem is rather involved, and it has been accomplished in 

 this case by means of the calculating table described, with the 

 results indicated on the figure. 



Single-phase Short-circuit Currents. Heretofore, we have 

 dealt with three-phase or balanced currents. Of late years the 

 tendency has been more and more toward the operation of systems 

 with transformers connected in Y and neutral grounded on the 

 high-voltage side. When a ground occurs on the line a three- 

 phase short circuit does not result but rather a single-phase short- 

 circuit. A brief outline of the method used in handling such 

 problems is given in the following, and for a more detailed study of 



