ABB RED615 Technical Manual page 549

1YHT530004D05 D
615 series
Technical Manual
Level detector 1
The measured phase currents are compared phasewise to the set Current value. If
the measured value exceeds the set Current value, the level detector reports the
exceeding 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.
Once the timer 1 and timer 2 are activated, CCBRBRF can be reset only after the
timers have reached the value set with the Retrip time and CB failure delay settings
respectively and the 150ms time elapse after the timer 1 and timer 2 has been
activated. The 150ms 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
either the values of the phase currents or 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 respectively.
Protection related functions
Section 5
543