468 



ELECTRICAL EQUIPMENT 



mit this emergency connection, each generator in operation is 

 permanently connected to a common synchronizing bus through 

 2 per cent reactors which keep the generators in step and also 

 serve the purpose of bus-tie reactors. When this scheme is em- 

 ployed with a bus divided into several sections the voltage regula- 

 tion is much better when there is current exchange than when 



Feeders 



o5 Per cent 



o 



o 



.5 Per cent 



J 



O+* 



! 



On 



s 



I Generator j < 



* 2 Per cent 



> 2 Per cent 



^Synchronizing Bus 

 FIG. 293. Stott System of Reactor Arrangement. 



ordinary bus-tie reactors are used. This is obvious from the fact 

 that to get the same protection as here obtained, 5 per cent bus- 

 tie reactors would have to be used and the energy exchanged 

 between two non-adjacent sections would suffer a large voltage 

 drop. If it is not considered necessary to protect the generators 

 themselves against current surges, the 5 per cent reactors may be 

 omitted. 



Number of Reactors. The following is considered the best 

 practice for locating reactors in various circuits: 



(a) For single-phase circuits a single reactor in one side of the 

 line. 



(b) For two-phase, four-wire circuits two reactors, one in one 

 side of the line of each phase. 



(c) For two-phase, three-wire circuits one reactor in each of the 

 outside lines (as distinguished from the neutral or common wire). 



(d) For three-phase circuits one reactor in each line. 



Size of Reactor. The selection of proper reactors for a system 

 requires, first of all, a complete investigation of the possible short 



