Siemens 6MD85, Manual

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Figure 7-14 Pickup/Dropout of the Circuit-Breaker Failure Protection Function (1/3-Pole Circuit Breaker)
Delay/Tripping
In a first step, tripping at the local circuit breaker can be repeated. Tripping is repeated after expiration of the
settable delay T1. With the 1/3-pole circuit breaker, you can set various T1 times for a 1-pole and multi-pole
start. In case of a 1-pole start, tripping can be repeated in a 1-pole or 3-pole way depending on the setting.
If the local CB was not yet tripped, for example, in the event of an external start of the circuit-breaker failure
protection, the trip logic of the circuit breaker itself is activated when the time delay T1 elapses.
Time delay T2 (backup tripping) can commence in parallel either with the start of time T1 or after expiration of
time T1.
With the 1/3-pole circuit breaker, you can set various T2 times for a 1-pole and multi-pole start.
If, with the 1/3-pole circuit breaker, the assigned 1-pole time is initially started by due to a 1-pole start and a
multiphase short circuit and multi-pole start occur subsequently, the corresponding multi-pole time is also
started so that the both times run in parallel. Tripping is determined by the time that expires first. If there is a
1-pole start with 3-pole trip repeat, the 3-pole T2 time is started.
If time delay T2 expires without a dropout of the function, a circuit-breaker failure is assumed and the backup
tripping signal
Tripping T2
is output. If the device is equipped with a protection interface, a transfer trip
signal can be sent to the opposite end if needed.
If the
>CB defect
input signal is valid, any repetition of the trip signal is suppressed, and the backup tripping
signal T2 is generated immediately (without delay). The binary input of the
>CB defect
input signal must be
activated for at least 20 ms before the signal becomes valid.
With help of the
CB failure pole
indication, you can determine the phase currents that are above the
threshold value at the tripping time T2.
Protection and Automation Functions
7.1 Circuit-Breaker Failure Protection
526 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017