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Fuse failure supervision (FFRW)
The delta current and delta voltage algorithm, detects a fuse failure if a sufficient neg-
ative change in voltage amplitude without a sufficient change in current amplitude is
detected in each phase separately. This check is performed if the circuit breaker is
closed (200 ms delay). Information about the circuit breaker position is brought to the
function input CBCLOSED through a binary input of the terminal.
The signal STDUDI is set to 1, if the measured voltage change exceeds its set value
∆ U> and if the measured current change does not exceed its pre-set value ∆ I<. If the
voltage is low in any phase (STULnN), the STDUDI signal is sealed in.
STDUDIL1
&
IL1>
STDUDIL2
&
IL2>
≥1
&
FFRW-CBCLOSED
FFRW-MCB
FFRW-DISC
)LJXUH 6LPSOLILHG ORJLF GLDJUDP IRU IXVH IDLOXUH VXSHUYLVLRQ IXQFWLRQ GXGW EDVHG
/RJLF
Signals STULnN are related to phase to earth voltages and become 1 when the respec-
tive phase voltage is lower than the set value.
The fuse failure supervision function is disabled (blocked) if:
•
The terminal is in TEST status (TEST-ACTIVE is high) and the function has been
blocked from the HMI (BlockFFRW=Yes)
•
The input signal FFRW-BLOCK is high
The FFRW-BLOCK signal is a general purpose blocking signal of the fuse failure su-
pervision function. It can be connected to a binary input of the terminal in order to re-
ceive a block command from external devices or can be software connected to other
STUL1N
>1
STUL2N
&
STDUDI
&
&
&
TEST
TEST-ACTIVE
&
BlockFFRW= Yes
6HFRQGDU\ V\VWHP VXSHUYLVLRQ
Tr‡ÃGh‡pu
150 ms
t
>1
&KDSWHU
FFRW-VTSU
>1
FFRW-VTSZ
>1
en02000645.vsd
159
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