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line from the other end onto a fault could lead to an improper operation of 60 with an open
breaker. If this is considered to be an important disadvantage, the
CB_CLOSED
input is to
be connected to FALSE. In this way only the second criterion can activate the delta
function.
The second condition requires the delta criterion to be fulfilled in one phase together with
a high current for the same phase. The measured phase current is used to reduce the risk
of a false fuse failure detection. If the current on the protected line is low, a voltage drop
in the system (not caused by the fuse failure) is not followed by a current change and a false
fuse failure can occur. To prevent this, the minimum phase current criterion is checked.
The fuse failure detection is active until the voltages return above the
Min Op voltage delta
setting. If a voltage in a phase is below the
Min Op voltage delta
setting, a new 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_V
and
FUSEF_3PH
are controlled according
to the detection criteria or external signals.
Table 768:
Fuse failure output control
Fuse failure detection criterion
Conditions and function response
Negative-sequence criterion
If a fuse failure is detected based on the negative
sequence criterion, the
FUSEF_V
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 "True", the
function activates the
FUSE_3PH
output signal.
The
FUSEF_V
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.
Table continues on next page
1MAC059074-MB A
Section 6
Supervision functions
615 series ANSI
869
Technical Manual
Summary of Contents for Relion 615 series
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