External Trip Commands
Functional Description
Direct Trip Commands
Two desired trip signals from external protection or supervision units can be incorporated into the processing
of the differential protection 7UT6x. The signals are couples into the device via binary inputs. Like the internal
protection and supervision signals, they can be annunciated, delayed, transmitted to the output trip relays, or
blocked individually. This allows to include mechanical protective devices (e.g. pressure switch, Buchholz
protection) in the processing of the protection relay.
The minimum trip command duration set for all protective functions are also valid for these external trip
commands (TMin TRIP CMD, address 851).
The logic diagram illustrates these “direct couplings”. Two of these functions are available. The message
numbers are illustrated for external trip command 1.
[logikdia-direkteinkoppung-bsp1-121102-st, 1, en_GB]
Figure 2-114 Logic Diagram of External Trip Feature — illustrated for external trip 1 (simplified)
Transformer Messages
In addition to the external trip commands as described above, some typical messages from power trans-
formers can be incorporated into the processing of the 7UT6x via binary inputs. This prevents the user from
creating user-specified annunciations.
These messages are known as the Buchholz alarm, Buchholz trip and Buchholz tank alarm as well as gassing
alarm of the oil (see Table 2-10).
Table 2-10
Transformer messages
No. Information Type of Information Description
390
>Gas in oil
EM >Warning stage from gas in oil detector
391
>Buchh. Warn
EM >Warning stage from Buchholz protection
392
>Buchh. Trip
EM >Tripp. stage from Buchholz protection
393
>Buchh. Tank
EM >Tank supervision from Buchh. protect.
Blocking Signal for External Faults
For transformers so-called sudden pressure relays (SPR) are occasionally installed in the tank which are meant
to switch off the transformer in case of a sudden pressure increase. Not only transformer failures but also high
traversing fault currents originating from external faults can lead to a pressure increase.
External faults are quickly recognised by the 7UT6x (also refer to Section
[OptUnresolvedLink]funktionsweise[/
OptUnresolvedLink], under “Add-on Restraint during External Faults”). A blocking signal can be created by
means of a CFC logic in order to prevent from erroneous trip of the SPR.
2.18
2.18.1
Functions
2.18 External Trip Commands
SIPROTEC 4, 7UT6x, Manual 251
C53000-G1176-C230-5, Edition 09.2016
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