If the fuse failure situation is present for more than 5 seconds and the setting parameter
SealIn
is
set to
Enabled
it will be sealed in as long as at least one phase voltage is below the set value
VSealInPU
. This will keep the BLKV and BLKZ signals activated as long as any phase voltage is
below the set value
VSealInPU
. If all three phase voltages drop below the set value
VSealInPU
and
the setting parameter
SealIn
is set to
Enabled
the output signal 3PH will also be activated. The
signals 3PH, BLKV and BLKZ signals will now be active as long as any phase voltage is below the
set value
VSealInPU
.
If
SealIn
is set to
Enabled
the fuse failure condition is stored in the non-volatile memory in the IED.
At start-up of the IED (due to auxiliary power interruption or re-start due to configuration change)
it uses the stored value in its non-volatile memory and re-establishes the conditions that were
present before the shut down. All phase voltages must be greater than
VSealInPU
before fuse
failure is de-activated and resets the signals BLKU, BLKZ and 3PH.
The output signal BLKV will also be active if all phase voltages have been above the setting
VSealInPU
for more than 60 seconds, the zero or negative sequence voltage has been above the
set value
3V0PU
and
3V2PU
for more than 5 seconds, all phase currents are below the setting
IDLDPU
(criteria for open phase detection) and the circuit breaker is closed (input 52a is
activated).
If a MCB is used then the input signal MCBOP is to be connected via a binary input to the N.C.
auxiliary contact of the miniature circuit breaker protecting the VT secondary circuit. The MCBOP
signal sets the output signals BLKV and BLKZ in order to block all the voltage related functions
when the MCB is open independent of the setting of
OpModeSel
or
OpDVDI
. An additional drop-
out timer of 150 ms prolongs the presence of MCBOP signal to prevent the unwanted operation of
voltage dependent function due to non simultaneous closing of the main contacts of the
miniature circuit breaker.
The input signal 89b is supposed to be connected via a terminal binary input to the N.C. auxiliary
contact of the line disconnector. The 89b signal sets the output signal BLKV in order to block the
voltage related functions when the line disconnector is open. The impedance protection function
does not have to be affected since there will be no line currents that can cause malfunction of the
distance protection.
Section 13 1MRK 502 066-UUS B
Secondary system supervision
740
Technical manual
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