Functions
2.25 Function Control and Circuit Breaker Test
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
447
2.25.1.2 Detection of the Circuit Breaker Position
For Protection Purposes
Information regarding the circuit breaker position is required by various protection and supplementary functions
to ensure their optimal functionality. This is, for example, of assistance for
• The echo function in conjunction with the distance protection with teleprotection (refer to Section 2.7),
• The echo function in conjunction with directional earth fault comparison scheme (refer to Section 2.9),
• Weak infeed tripping (refer to Section 2.11.2),
• The high-current instantaneous tripping (refer to Section 2.14 ),
• The circuit breaker failure protection (refer to Section 2.22),
• Verification of the dropout condition for the trip command (see Section „Terminating the Trip Signal“).
The device is equipped with a circuit breaker position logic (Figure 2-222) which offers different options depend-
ing on the type of auxiliary contacts provided by the circuit breaker and on how they are connected to the
device.
In most cases it is sufficient to report the status of the circuit breaker with its auxiliary contacts to the device via
binary input. This always applies if the circuit breaker is only switched 3-pole. Then the NO auxiliary contact of
the circuit breaker is connected to a binary input which must be configured to the input function
„>CB 3p
Closed“
(No. 379). The other inputs are then not used and the logic is restricted in principle to simply forward-
ing the input information.
If the circuit breaker poles can be switched individually, and only a parallel connection of the NO individual pole
auxiliary contacts is available, the relevant binary input (BI) is allocated to the function
„>CB 3p Open“
(no.
380). The remaining inputs are not used in this case.
If the circuit breaker poles can be switched individually and if the individual auxiliary contacts are available, an
individual binary input should be used for each auxiliary contact if this is possible and if the device can and is
to trip 1-pole. With this configuration, the device can process the maximum amount of information. Three binary
inputs are used for this purpose:
•
„>CB Aux. L1“
(No. 351) for the auxiliary contact of pole L1,
•
„>CB Aux. L2“
(No. 352) for the auxiliary contact of pole L2,
•
„>CB Aux. L3“
(No. 353) for the auxiliary contact of pole L3.
The inputs No. 379 and No. 380 are not used in this case.
If the circuit breaker can be switched individually, two binary inputs are sufficient if both the parallel as well as
series connection of the auxiliary contacts of the three poles are available. In this case, the parallel connection
of the auxiliary contacts is routed to the input function
„>CB 3p Closed“
(No. 379) and the series connection
is routed to the input function
„>CB 3p Open“
(No. 380).
Please note that Figure 2-222 shows the complete logic for all connection alternatives. For each particular ap-
plication, only a portion of the inputs is used as described above.
The eight output signals of the circuit breaker position logic can be processed by the individual protection and
supplementary functions. The output signals are blocked if the signals transmitted from the circuit breaker are
not plausible: for example, the circuit breaker cannot be open and closed at the same time. Furthermore, no
current can flow over an open breaker contact.
The evaluation of the measuring quantities is according to the local conditions of the measuring points (see
Section 2.1.4.1 at margin heading „Circuit Breaker Status“).
The phase currents are available as measuring quantities. A flowing current excludes that the circuit breaker
is open (exception: A fault between current transformer and circuit breaker). If the circuit breaker is closed, it
may, however, still occur that no current is flowing. The decisive setting for the evaluation of the measuring
quantities is
PoleOpenCurrent
(address
1130
) for the presence of the currents.
