ABB RELION Series Technical Manual page 473

1MRS758755 A
REC615 and RER615
Technical Manual
of the value to the start, retrip and backup trip logics. The parameter should be set low
enough so that breaker failure situations with small fault current or high load current
can be detected. The setting can be chosen in accordance with the most sensitive
protection function to start the breaker failure protection.
Level detector 2
The measured residual current is compared to the set Current value Res. If the
measured value exceeds the set Current value Res, the level detector reports the
exceeding of the value to the start and backup trip logics. In high-impedance earthed
systems, the residual current at phase-to-earth faults is normally much smaller than the
short circuit currents. To detect a breaker failure at single-phase earth faults in these
systems, it is necessary to measure the residual current separately. In effectively
earthed systems, also the setting of the earth-fault current protection can be chosen at
a relatively low current level. The current setting should be chosen in accordance with
the setting of the sensitive earth-fault protection.
Start logic
The start logic is used to manage the starting of the timer 1 and timer 2. It also resets
the function after the circuit breaker failure is handled. On the rising edge of the
START input, the enabling signal is send to the timer 1 and timer 2.
Function resetting is prevented during the next 150 ms. The 150 ms time elapse is
provided to prevent malfunctioning due to oscillation in the starting signal.
In case the setting Start latching mode is set to "Level sensitive", the CCBRBRF is
reset immediately after the START signal is deactivated. The recommended setting
value is "Rising edge".
The resetting of the function depends on the CB failure mode setting.
• If CB failure mode is set to "Current", the resetting logic further depends on the
CB failure trip mode setting.
• If CB failure trip mode is set to "1 out of 3", the resetting logic requires that
the values of all the phase currents drop below the Current value setting.
• If CB failure trip mode is set to "1 out of 4", the resetting logic requires that
the values of the phase currents and the residual current drops below the
Current value and Current value Res setting respectively.
• If CB failure trip mode is set to "2 out of 4", the resetting logic requires that
the values of all the phase currents and the residual current drop below the
Current value and Current value Res setting.
• If CB failure mode is set to the "Breaker status" mode, the resetting logic requires
that the circuit breaker is in the open condition.
• If the CB failure mode setting is set to "Both", the resetting logic requires that the
circuit breaker is in the open condition and the values of the phase currents and the
residual current drops below the Current value and Current value Res setting
respectively.
The activation of the BLOCK input resets the function.
Protection related functions
Section 5
467