ABB IEMMU21 Bailey Controller Base Rack
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 I0> and a high-set earth fault stage I0>>.
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
I0> or the high-set earth-fault stage I0>> 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 t0> 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 t0>> 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 blocked1) 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.
1)From program version 183 B and later this
function can be switched off with switch 2 of
the extended switchgroup, SGX. By default
this function is switched off.
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.