520 



ELECTRICAL EQUIPMENT 



Consider, for example, that one of the two lines is shorted at 

 S, near Station A. The dotted arrows then indicate the changes 

 that take place. Power flows out from Station B over both lines. 

 The weaker influence of line No. 1 tends to prevent any action 

 of these relays but it may be sufficiently overpowered by the heav- 

 ier current in line No. 2, in which case the relay 26 will operate. 



Station "A" 



i 



Oil Circuit Breaker 



Current 

 Transformer 



Tie Lineal 



Direction of Current 

 to Operate Relay 



' 



Direcfion of Current 

 to Operate Relay 



| | Oil Circuit Breake* 



Station U B" 



FIG. 325. Simplified Connection Diagram of Interconnected Reverse-power 



Relays. 



At the same time any force exerted in the relay 16 will simply 

 oppose the closing of its contacts. The same is true of relay la. 

 Consequently neither oil switch of line No. 1 will be disturbed. 



The effect in relay 2a, however, is very different. Here the 

 currents are both in the proper direction to operate the relay. 

 This relay, therefore, trips its oil switch immediately, and, return- 



