Siemens siprotec 7SA522, Руководство пользователя

Страница: 265 / 628

Functions
6-117
7SA522 Manual
C53000-G1176-C119-2
Via the setting parameter
/LQH&RQILJ
(address ), the device is informed as
to whether it has one or two opposite line ends.
If the unblock frequency fu is received without interference, it is — in the case of three
terminal lines both receive signals combined by
AND — used to release tripping. If the
transmitted signal does not reach the other line end because the short circuit on the
protected feeder causes too much attenuation or reflection of the transmitted signal,
the unblock logic takes effect: neither the unblock signal “
>
()8%XE
” nor the mon-
itoring signal “
>
() 8%EO
” are received. In this event, the release state in the logic
is set after a security margin of 20 ms. With the timer stage 100/100 ms this release
is however removed after a further 100 ms. If the interference signal disappears again
the quiescent state is reached again after a further 100 ms (reset delay of the timer
100/100 ms). On three terminal lines, the unblock logic can be controlled via both re-
ceive channels.
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” (refer to Sub-section 6.6.1.4).
On lines where there is only a single sided infeed or where the starpoint is only earthed
behind one line end, the line end without zero sequence current cannot generate a
permissive signal, as fault detection does not take place there. To also ensure tripping
by the directional comparison in this case the device has special features. This “Weak
Infeed Function” is referred to in Sub-section 6.6.1.5. It is activated when a signal is
received from the opposite line end — on three terminal lines, from at least one of the
opposite ends — without the device recognizing an earth fault.
The circuit breaker can also be tripped at the line end with no or only weak infeed. This
“Weak-Infeed Tripping” is referred to in Section 6.7.
Figure 6-68 Logic diagram of the unblocking scheme (one line end)
EF Pickup
&
EF forward
6HQG3URORQJ
T 0
&
≥
1
&
Trip command
&
Transient blocking
&
≥
1
&
≥
1
≥
1
100 100 0 20
ms ms
>EF UB ub 1
&
&
&
&
Two terminals
Three terminals
Two terminals
Three terminals
„1“
/LQH&RQILJ
Two terminals
Three terminals
≥
1
≥
1
&
&
≥
1
≥
1
EF Telep. off
1313 >EF TeleprotBLK
1320
>EF UB bl 1 1321
>EF UB bl 2 1323
>EF UB ub 2
1322
EF Telep. OFF 1381
EF Tele SEND 1384
Echo function
section 6.6.1.5
weak infeed trip
section 6.7
EF Enable Trip