518 



ELECTRICAL EQUIPMENT 



Figs. 323 and 324 give the connections for this type of relay 

 both for ungrounded and grounded three-phase circuits. Three 

 potential transformers to be used in the latter case if the volt- 

 ampere load is too great for only two. 



Interconnected Reverse Power Relays. For two or more parallel 



Fuse] 



Auxiliary Switch) 

 Trip CoU 3 



Source 

 2 1 



FIG. 323. Connections for Polyphase Induction-type Reverse-power Relay 

 for Ungrounded Three-phase Circuits. 



tie lines, over which energy may normally be fed in either direction, 

 reverse power relays with interconnected current coils may be 

 used at each end of the tie lines. The interconnection of the cur- 

 rent coils is such that the influence of each circuit on its relay will 

 be completely overcome by the other circuit so long as conditions 

 are normal. If a short should occur in one line, the unbalanced 



