Siemens 7SG164 Ohmega 400 Series Manual page 145

POR2
Title Permissive Overreach Scheme using Zone 2
Art No 2615S81151
Author Ken Nickerson
Clear the reach extension controls as that scheme is not in use.
FALSE
Generate the general trip output from the delayed distance protection elements
Z1D
Z2D
Z3D
We qualify signal receive w ith the Carrier Receive Guard input and stretch the resultant signal
CARRIERFAIL
SIGRECV1
Current Reversal Logic
If there is a fault on an adjacent (parallel) feeder, then w e may see it as a reverse fault, but our remote relay sees it as a forw ard fault and
sends us a signal. There is then a risk of a race betw een dropoff of the signal and pickup of our zone 1 w hich may result in a trip, unnecessarily
killing our feeder. Current reversal guard (CRG) prevents this by blocking operation of the local end for a selected period after dropoff of the
reverse fault if w e have seen Zone4 and signal recv and our breaker is closed. We also create a CB Closed matrix tag here.
Z4G
EXTSIGRECV1
CBCLOSED
Weak Infeed Logic
Under certain system conditions, such as on radial systems, or w here the source capacity at one end of a line is reduced for some reason,
then there may not be sufficient fault current flow ing for the relay to determine the fault impedance. Under these circumstances w e use w eak
infeed protection. This uses the fact that the relay at the remote (strong) end can see a fault and so sends us a signal, but w e cannot see a
fault. In addition, our CB must be closed. We use these criteria to say that there may be a fault in front of us that w e cannot see. This allow s
us to send a signal to the remote end to permit it to trip, and also optionally to trip the local end.
WILowV1
Z3G
EXTSIGRECV1
CBCLOSED
WITripping
©2011 Siemens Protection Devices Limited
Z1XEF
Z1XPF
1
SREXTEND
0 / 1
&
PORCurrentReversalTimer
&
1 / 200
&
7SG1641 Ohmega 402 60 Diagrams
SOLOTRIP
1 EXTSIGRECV1
PORCRGuard
NOCRG
&
PORWeakInf eed
PORWITRIP
Chapter 11 Page 16 of 18