Functions
114
7SS52 V4 Manual
C53000-G1176-C182-3
5.3 Circuit Breaker Failure Protection
The circuit breaker failure protection (CBF) function in the SIPROTEC 7SS52 V4 dis-
tributed busbar and breaker failure protection detects a failure of the circuit breaker
either in the event of a feeder short-circuit or a busbar short-circuit.
• In the event of a feeder short-circuit, a breaker failure leads to selective isolation of
the bus zone to which the feeder with the defective breaker is allocated. In addition
a transfer trip (intertrip) signal is issued in order to trip the remote feeder terminal,
too. The available operating modes are described in Chapter 5.3.5.2, page 119.
Each mode can be set selectively for each bay. Thus the function can be matched
optimally to existing conditions (type of bay, short-circuit currents etc.).
• In the event of a circuit breaker failure with a busbar short-circuit, the infeed from
the remote feeder terminal has to be interrupted. For this purpose the 7SS52 V4
issues a transfer trip signal.
5.3.1 Characteristics for the Circuit Breaker Failure Protection
Standard
characteristic
The unbalanced mode has two separate parameter sets, one for 1-pole high-resist-
ance earth faults and the other for multi-pole faults. Figure 5-16, page 114, shows the
characteristics and the setting parameters.
Earth fault charac-
teristic
For the detection of high-resistance earth faults, tripping characteristics with increased
sensitivity for breaker failure are provided. For these more sensitive characteristics the
parameters
I> BF-EF (XX19/CU) and Is< BF - EF (6202A/CU) apply. The stabilizing factor is
identical with the standard characteristic. The marshallable binary input ">EF char-
act." (FNo. 10478/CU) in the central unit allows to switch over between character-
istics, provided that the parameter EF charact. (6320A/CU) is set to released.
Figure 5-16, page 114, shows the characteristics and the setting parameters.
Figure 5-16 Characteristics of the breaker failure protection
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