Siemens siprotec 7SD5 User Manual page 189

100 ms (drop-off delay of the timer stage 100/100 ms) the quiescent state is reached
again, i.e. the direct release path to the signal „Unblock L1" and thereby the usual
release is possible.
If none of the signals is received for a period of more than 10 s the alarm „Dis.T.UB
Fail1" is generated.
During disturbance of the signal transmission path, the overreaching zone Z1B may
be activated by an automatic reclosure (internal or external) via the binary input
„>Enable ARzones".
The occurrence of erroneous signals resulting from transients during clearance of ex-
ternal faults or from direction reversal resulting during the clearance of faults on par-
allel lines, is neutralized by the „Transient Blocking".
On feeders with single-sided infeed, the line end with no infeed cannot generate a
release signal, as no fault detection occurs there. To achieve tripping by the permis-
sive overreach transfer scheme even in this case, the device contains a special func-
tion. This „Weak Infeed Function" (echo function) is referred to in Section „Measures
for Weak and Zero Infeed". It is activated when a signal is received from the opposite
line end — in the case of three terminal lines from at least one of the opposite line ends
— without the device having detected a fault.
7SD5 Manual
C53000-G1176-C169-1
2.7 Teleprotection for Distance Protection (optional)
189