ABB Relion REC615, Техническое руководство

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TRRET
BLOCK
CB_FAULT
TRBU
Back-up
trip
logic
POSCLOSE
START
Io
Retrip
logic
Level
detector
2
Level
detector
1
I_A
I_B
I_C
t
Timer 2
t
Timer 3
CB_FAULT_AL
Start
logic
t
Timer 1
Figure 237: Functional module diagram
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.
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.
Protection related functions 1MRS758755 C
482 REC615 & RER615
Technical Manual