4
Earth-fault unit
The relay module features a circuit breaker
failure protection (CBFP) unit. The CBFP unit
generates a trip signal via TS1 after a set operate
time 0.1...1 s, following the main trip signal
TS2, if the fault has not been cleared before the
set operate time has elapsed. The output contact
of the CBFP unit is normally used for tripping
an upstream circuit breaker. The CBFP unit can
also be used for tripping via redundant trip
circuits of the same circuit breaker, if the circuit
breaker is provided with two trip coils. The
circuit breaker failure protection unit is alerted/
set out of operation with switch SGF1/4.
The relay can be given two sets of setting values,
the main settings and the second settings. Switch-
ing between main settings and second settings
can be done in three different ways, i) with a
command V150 via the serial port, ii) with a
command via the external control input BS or
manually by changing a parameter in submenu
4 of register A.
Circuit breaker
failure protection
unit
Remote setting
The non-directional earth-fault unit of the relay
module SPCJ 4D29 is a single-pole earth-fault
unit. It contains two earth-fault stages, i.e. a
low-set earth-fault stage I
0
> and a high-set earth-
fault stage I
0
>>.
The low-set or high-set earth-fault stage starts,
if the measured current exceeds the set start
current value. When the stage starts it generates
a start signal SS1 or TS1 and simultaneously the
digital display on the front panel indicates start-
ing. If the earth-fault situation lasts long enough
to exceed the set operate time, the stage operates
and generates a trip signal TS2. At the same time
the operation indicator TRIP is lit with red
light. The red operation indicator remains lit
although the stage resets. The indicator is reset
by pushing the RESET push-button. By proper
configuration of the output relay switchgroups
an additional auxiliary trip signal TS1 can be
obtained.
The operation of the low-set earth-fault stage
I
0
> or the high-set earth-fault stage I
0
>> can be
blocked by routing a blocking signal BS to the
earth-fault unit. The blocking configuration is
set with switchgroup SGB.
The operation of the low-set earth-fault stage
can be based on definite time or inverse time
characteristic. The operation characteristic is
selected with the SGF/6…8 switches. At defi-
nite time operation characteristic the operate
time t
0
> is directly set in seconds within the
range, 0.05...300 s. When the inverse time
operation characteristic (IDMT) is selected, four
internationally standardized and two comple-
mentary time/current curves are available. The
selector switches SGF1/ 6...8 are also used for
selecting the desired operation characteristic.
The setting range of the operate time t
0
>> of the
high-set earth-fault stage is 0.05…300 s.
Note!
The operation of the low-set stage based on
inverse time characteristic will be blocked by
starting of the high-set stage. Then the operate
time of the earth-fault unit is determined by the
set operate time of the high-set stage at heavy
fault currents.
The operate signal of the two earth-fault stages
is provided with a latching feature (switch SGB/7)
which means that the operate signal TS2 is kept
high after an operation, although the earth-fault
stage resets. The TS2 signal is reset by pushing
the RESET and PROGRAM push-buttons si-
multaneously or via the serial port using the
command V101, see chapter "Selector switches",
page 9.
The high-set earth-fault stage can be set out of
operation with switch SGF2/6. When the high-
set stage is set out of operation the display shows
"- - -", indicating that the start current setting is
infinite.
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