ABB RER620, Technical Manual

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1MAC309294-MB F
Section 6
Condition monitoring functions
RER620 379
Technical Manual
Table 331: Fuse failure output control
The activation of the
BLOCK
input deactivates both
FUSEF_U
and
FUSEF_3PH
outputs.
6.2.5 Application
Some protection functions operate on the basis of the measured voltage value in the relay
point. These functions can fail if there is a fault in the measuring circuits between the
voltage transformers and the relay.
A fault in the voltage measuring circuit is referred to as a fuse failure. This term is
misleading since a blown fuse is just one of the many possible reasons for a broken circuit.
Fuse-failure detection criterion Conditions and function response
Negative phase sequence criterion If a fuse failure is detected based on the negative
phase-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
Seal in
voltage setting with Enable seal in turned to “ Yes ” ,
the function activates the
FUSE_3PH
output signal.
The
FUSEF_U
output signal is also activated if all the
phase voltages are above the
Seal in voltage
setting
for more than 60 seconds and at the same time the
negative sequence voltage is above
Neg Seq
voltage Lev
for more than 5 seconds, all the phase
currents are below the
Current dead Lin Val
setting
and the circuit breaker is closed, that is,
CB_CLOSED
is TRUE.
Current and voltage delta function criterion If the current and voltage delta criterion detects a
fuse failure condition, but all the voltages are not
below the Seal in voltage setting, only 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
Seal in
voltage setting with Enable seal in turned to “ Yes ” ,
the function activates the
FUSE_3PH
output signal.
External fuse-failure detection The
MINCB_OPEN
input signal is supposed to be
connected through a 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 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.
It is recommended to always set Enable seal in to “Yes”. This secures that
the blocked protection functions remain blocked until normal voltage
conditions are restored if the fuse-failure has been active for 5 seconds, that
is, the fuse failure outputs are deactivated when the normal voltage
conditions are restored.