Siemens 7SG164 Ohmega 400 Series Manual page 144

CB Echo
If the Circuit Breaker at this end is open, and w e see SigRx but no fault, then w e reflect the signal straight back to the other end to
allow it to trip.
To avoid a lockup situation w here CB Echoes at each end reinforce each other and prevent SigSend from dropping off w e limit the
duration of the CB Echo signal and keep the CB Echo Required signal asserted until the trigger condition has been absent for one
second.
CBCLOSED
EXTSIGRECV1
Z1G
PORECHOPulseGen
PORCBEchoReqd
This is the echo pulse monostable. This stretches the single period pulse generated above into one of user
specified w idth (default 250ms).
POREchoPulse
Sig Send Logic
We generate a signal to send to the remote relay if w e have Zone 1 picked up but no current reversal guard, or w e have an
echo pulse, or w e have a w eak infeed condition.
Z1G
NOCRG
POREcho
PORWeakInf eed
Aided Trip Logic
Z1G
EXTSIGRECV1
NOCRG
PORWITRIP
©2011 Siemens Protection Devices Limited
PORAntiPingPongTimer
&
1 / 1000
&
PORCBEchoPulseWidth
1 / 250
&
SSEXTEND
1
&
7SG1641 Ohmega 402 60 Diagrams
1 PORCBEchoReqd
POREchoPulse
PORECHOPulseGen
1 POREcho
1 / 1
1 SIGSEND1
1 AIDEDTRIP
Chapter 11 Page 15 of 18