ABB RELION REX640 Technical Manual page 1236

Section 6
Supervision functions
1230
fuse failure detection for that phase is not possible until the voltage returns above the
setting value.
Decision logic
If voltages are Wye-connected, it is recommended to scale the default
values of voltage-based settings with 1/sqrt(3) because the default
setting values apply for Delta-connected settings.
The fuse failure detection outputs FUSEF_U and FUSEF_3PH are controlled
according to the detection criteria or external signals.
Table 1158: Fuse failure output control
Fuse failure detection criterion
Negative-sequence criterion
Current and voltage delta function criterion
External fuse failure detection
Conditions and function response
If a fuse failure is detected based on the negative
sequence criterion, the FUSEF_U output is
activated.
If the fuse failure detection is active for more than
five seconds and at the same time all the phase
voltage values are below the set value of the
in voltage setting with Enable seal in turned to
"True", the function activates the FUSE_3PH
output signal.
The FUSEF_U output signal is also activated if all
the phase voltages are above the
setting for more than 60 seconds and at the same
time the negative sequence voltage is above
Seq voltage Lev for more than 5 seconds, all the
phase currents are below the
setting and the circuit breaker is closed, that
is,CB_CLOSED is TRUE.
If the current and voltage delta criterion detects a
fuse failure condition, but all the voltages are not
Seal in voltage setting, only the
below the
FUSEF_U output is activated.
If the fuse failure detection is active for more than
five seconds and at the same time all the phase
voltage values are below the set value of the
in voltage setting with Enable seal in turned to
"True", the function activates the FUSE_3PH
output signal.
The MINCB_OPEN input signal is supposed to be
connected through a protection relay binary input
to the N.C. auxiliary contact of the miniature circuit
breaker protecting the VT secondary circuit. The
MINCB_OPEN signal sets the FUSEF_U output
signal to block all the voltage-related functions
when MCB is in the open state.
The DISCON_OPEN input signal is supposed to be
connected through a protection relay binary input
to the N.C. auxiliary contact of the line
disconnector. The DISCON_OPEN signal sets the
FUSEF_U output signal to block the voltage-
related functions when the line disconnector is in
the open state.
1MRS759142 C
Seal
Seal in voltage
Neg
Current dead Lin Val
Seal
REX640
Technical Manual