Functions
168
7SS52 V4 Manual
C53000-G1176-C182-3
5.9.3
Operating States "Bay Out of Service", "Maintenance Mode"
The parameter
(
XX12/CU
) is used to select the operating status of the
bay unit.
Bay out of service /
in service
The allocation of a feeder current to a selective measuring system (= bus zone) takes
place due to the disconnector image ("isolator replica"). The service function "bay out
of service" causes that this allocation is generally cancelled. In 2-bay couplers, this
status is automatically assumed for both coupler bay units. Therefore the disconnec-
tors of the affected bay unit in the internal disconnector image are processed as open.
Further the disconnector supervision of the bay and resulting messages are blocked.
Even if all disconnectors of a feeder are open, the allocation of the feeder to the check
zone (=disconnector-independent measuring system) remains however, as long as
the bay unit is switched on.
The service function "bay out of service" can naturally be used, if for the test of the
feeder protection, which uses the same transducer core, a test current will be injected.
If for example a busside isolator remains closed and only the circuit breaker and the
line side isolator (without beeing monitored by the bus bar protection) are open, a test
current would be assigned to a measuring system.
With "bay out of service" a processing of this test current (by the selective measuring
systems) and thereby a possible false tripping is prevented. That test current remains
in the check zone measuring system and may lead to a pick up of the "differential cur-
rent supervision of the check zone". Therefore it is recommended to set the reaction
on a pick up of the "differential current supervision of the check zone" to "alarm only".
Additionally, the binary inputs for the breaker failure protection are no longer proc-
essed. An inadvertent tripping of a busbar, e.g. in the operating mode "
external
",
(
XX15
/
CU
), is thus prevented.
"Bay out of service" represents thus a precautionary measure for the bus bar protec-
tion with secondary work in the bay and no test function of the bus bar protection, par-
ticularly the bay unit.
A bay unit in condition "bay out of service" is to be left switched on if possible. The
safety function of the check zone is thus still available. Switching off is only necessary
with defect of the bay unit or the optical fiber connection. The bay is thus taken out of
the protection completely and resulting annunciations or blockings prevented. As
preparation the feeder has to be switched off primary and be faded out by "bay out of
service" from the bus bar protection. If the switching off happens without previous "bay
out of service", a blocking according to the selected settings of the bus bar protection
takes place.
Caution!
Switching a bay unit into the condition "bay out of service" requires that the feeder is
actually primary out of operation, i.e. no current flow can take place in the feeder.
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