Siemens SIPROTEC 4 7UT6 Series, Руководство пользователя

Страница: 273 / 684

Disconnection of Measuring Locations
Functional Description
During maintenance work, or when parts of the system are shut down during operation, it is sometimes
necessary to suspend the processing of individual measuring locations by the differential protection system.
For maintenance work on the circuit breaker CBC in
Figure 2-126 , for instance, the breaker would be isolated
by opening the adjacent isolators.
The main protected object transformer is in this example fed on side S1 through measuring locations M1 and
M2, on side S2 lies the measuring location M3. Assuming the measuring location M2 should now be
suspended due to the maintenance work on the circuit breaker. If this information is sent to the device
through a binary input — in this case
>disconnect M2
–, the measuring location will no longer be included
in the formation of the differential protection values. The measuring location is disconnected, i.e. any kind of
work can be performed there without affecting any operating function of the sides, for example, the differen-
tial protection.
[anord-mit-einhalb-ls-270503-st, 1, en_GB]
Figure 2-126
Arrangement with 1 1 /
2
circuit breakers (3 breakers for 2 transformer feeders)
Any measuring location can be disconnected by means of an appropriate binary input. In 1-phase busbar
protection, such a binary input can be used for each feeder.
The disconnection works only in the specified frequency range of the protection, i.e at f
N
= 50/60 Hz from 10
to 66 Hz and at f
N
= 16.7 Hz (only 7UT613/63x) from 10 to 22 Hz. If the current criterion is disabled via binary
input
>disconn. I>=0
, the specified frequency range is also not applicable. The activation is thus not
suited for blocking the protection during startup of a machine. Instead, the blocking features provided in the
protection functions must be used.
The isolation becomes effective only if no current is flowing through the measuring location to be isolated at
the moment the disconnection is started. This is ensured by checking whether the current arriving from the
measuring location has dropped below the threshold
PoleOpenCurr.M1
,
PoleOpenCurr.M2
to
PoleO-
penCurr.M5
of the measuring location. Once the disconnection has become effective, this fact is reported by
a binary output, e.g. with the indication
M2 disconnected
. The current threshold is no longer checked from
then on.
The disconnection ends when the binary input is deactivated. This requires, that no current is flowing at the
moment the disconnection is ended.
One can evade the condition that the disconnection mode can only be started or ended when no current is
flowing via the measuring location. If you wish to start and end the disconnection mode even in case of
current flow, you have to activate — together with the corresponding binary input (
“>disconnect Mx”
) —
the input
>disconn. I>=0
(FNo 30361). This can be done by means of a logical CFC-combination. To
ensure an effective change from connection to disconnection, the input
>disconn. I>=0
should be activate
before the input
“>disconnect Mx”
.
2.21
2.21.1
Functions
2.21 Disconnection of Measuring Locations
SIPROTEC 4, 7UT6x, Manual 273
C53000-G1176-C230-5, Edition 09.2016