Siemens 7SG12 DAD-N - Page 62

7SG12 DAD N Applications Guide
A Check Zone relay is also sometimes installed on single busbar systems of high importance.
The outputs of the relays protecting each Busbar zone are then connected in series with the Check Zone
relay’s outputs. Only when both operate will a trip be issued.
106
104
186
184
Main
1
Res
206
204
286
284
Main
2
106
104
186
184
206
204
286
284
RESERVE
MAIN 1 MAIN 2
Check
180 280205105
Figure 8 – Check Zone Relay
©2010 Siemens Protection Devices Limited Chapter 5 Page 8 of 16