As soon as any fuse failure situation is detected, signals FuseFailDetZeroSeq,
FuseFailDetNegSeq or FuseFailDetDUDI, and the specific functionality is released,
the function will activate the output signal BLKU. The output signal BLKZ will be
activated as well if the internal dead phase detection, DeadLineDet1Ph, is not
activated at the same time. The output BLKU can be used for blocking voltage related
measuring functions (under voltage protection, energizing check, and so on). The
output BLKZ shall be used to block the impedance protection functions.
If the fuse failure situation is present for more than 5 seconds and the setting parameter
SealIn is set to On it will be sealed in as long as at least one phase voltages is below
the set value USealIn<. This will keep the BLKU and BLKZ signals activated as long
as any phase voltage is below the set value USealIn<. If all three phase voltages drop
below the set value USealIn< and the setting parameter SealIn is set to On the output
signal 3PH will also be activated. The signals 3PH, BLKU and BLKZ will now be
active as long as any phase voltage is below the set value USealIn<.
If SealIn is set to On the fuse failure condition lasting more then 5 seconds 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 restored above USealIn< before fuse failure is de-
activated and resets the signals BLKU, BLKZ and 3PH.
The output signal BLKU will also be active if all phase voltages have been above the
setting USealIn< for more than 60 seconds, the zero or negative sequence voltage has
been above the set value 3U0> and 3U2> for more than 5 seconds, all phase currents
are below the setting IDLD< (criteria for open phase detection) and the circuit breaker
is closed (input CBCLOSED 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 BLKU and BLKZ in
order to block all the voltage related functions when the MCB is open independent of
the setting of OpMode or OpDUDI. 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 DISCPOS is supposed to be connected via a terminal binary input to
the N.C. auxiliary contact of the line disconnector. The DISCPOS signal sets the
output signal BLKU 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.
1MRK502052-UEN B Section 13
Secondary system supervision
617
Technical manual
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