CURRENT-LIMITING REACTORS 465 



Both b and t include the thickness of insulation or, if the turns are 

 air insulated, are equal to the pitch of the winding times the num- 

 ber of turns. If there is only one turn, the values are equal to the 

 diameter of the wire. 



N = total number of turns in coil; 



F' and F" are correction factors depending on the coil shape; 



F' = 



106+10.7*+ 1.4r' 



The reactance, X, is equal to 2irfL ohms. 



Location. Reactors may be located in the system in such a 

 way that they will not only reduce the mechanical strains due to 

 short circuit, but will also practically localize its effect to the cir- 

 cuit or section where it occurs. They may thus be placed in the 

 generator leads, between the bus-sections, in the low-tension trans- 

 former leads or in outgoing low-tension feeders. Which one of the 

 above locations or combinations thereof is preferable depends upon 

 a number of conditions, each location having its advantages and 

 disadvantages. 



Generator Reactors. With reactors in the generator leads 

 (Fig. 289) the current flowing in the armature winding of the 

 generator is limited, and this 

 method, therefore, gives protec- 

 tion to the generator itself. It //^^ ?VKA 



necessarily also limits the cur- 1 . , 1 



rent that can flow into any 

 short-circuit beyond the react- 

 ors, inasmuch as the amount of 

 current which can flow is limited 



to what the generators can sup- ~ IQ 289 ._G enerator Reactors, 

 ply. An objection to generator 

 reactors is the fact that a short-circuit on or near the busbars 

 will cause a voltage drop on all the lines or feeders connected 

 thereto. If the short is severe, the voltage may drop to zero 

 and this, of course, will cause all the synchronous apparatus con- 

 nected to the system to drop out of step. It is, therefore, evi- 



i 

 I 



