4
Filter characteristics
of the measuring
inputs
A low-pass filter suppresses the harmonics of the
phase currents and the earth-fault current meas-
ured by the module. Figure 1 shows the signal
suppression as a function of the frequency.
dB 10
0
-10
-20
-30
-40
0 1 2 3 4 5 6 7
f / f n
Fig. 1. Filter characteristics of the measuring
inputs of the module SPCJ 4D28
Phase discontinuity
protection unit
The overcurrent and earth-fault relay module
SPCJ 4D28 is provided with a phase disconti-
nuity protection unit which monitors the mini-
mum and maximum phase currents. The differ-
ence between these currents is calculated from
the expression
∆
I = (I
max
-I
min
)/I
max
x 100%. The
phase discontinuity protection is not in use
when the measured currents fall below 0.1 x I
n
.
The phase discontinuity protection stage starts,
if the current difference exceeds the set start
current
∆
I of the stage. Should the duration of
the phase discontinuity situation exceed the set
operate time t
∆
> of the stage the stage operates
issuing an operate signal, which can be routed to
the desired output relay. At the same time a red
operation indicator code is lit on the display.
The phase discontinuity protection stage can be
set out of operation completely, if not needed.
When the stage is set out of operation the set
start current is displayed with three dashes "- - -".
The operation of the phase discontinuity pro-
tection stage can be inhibited by an external
control signal BS1 applied to the relay module.
The external blocking signal is configured with
switch SGB1/6.
Circuit breaker
failure protection
unit
The overcurrent and earth-fault relay module
SPCJ 4D28 is provided with a circuit breaker
failure protection unit (CBFP) which provides a
trip signal TS1 within 0.1...1 s after the trip
signal TS2, TS3 or TS4 has been delivered,
provided the fault still persists after the time has
elapsed. The CBFP normally controls the cir-
cuit breaker which precedes the circuit breaker
in question. The CBFP can also be used to
establish a redundant trip system by using two
trip coils in the circuit breaker and controlling
one of the coils with TS2, TS3 or TS4 and the
other with TS1. The switches SGF4/5...7 are
used for activating the circuit breaker failure
protection. The operate time is set in submenu
5 of register A.
Output signals
Switchgroups SGR1...11 are used for routing
the start or trip signals of any protection stage
to the desired start outputs SS1...SS4 or trip
outputs TS...TS4.
The output signals TS1…TS4 can be assigned
a self-holding function with switches SGF4/
1…4. In this case the output signal remains
active, although the signal that caused the op-
eration resets. The resetting functions are ex-
plained in paragraph "Resetting". The TRIP
indicator on the front panel can be set to be lit
on activation of any of the output signals. The
operation indicator remains lit after the output
signal has disappeared. The functions are se-
lected with switchgroup SGF5.
Содержание SPAA 341 C /E351
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