Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
89
Inrush Restraint
When applying the protection device to transformers where high inrush currents are to be expected, the
7SJ62/64 can make use of an inrush restraint function for the overcurrent elements
50-1
,
51
,
50N-1
and
51N
as
well as the non-directional overcurrent elements.
Inrush restraint is only effective and accessible if address
122
InrushRestraint
was set to
Enabled
. If this
function is not required, then
Disabled
is set. In address
2201
,
INRUSH REST.
the function is switched
ON
or
OFF
jointly for the overcurrent elements .
50-1 PICKUP
,
51 PICKUP
,
50N-1 PICKUP
and
51N PICKUP
The inrush restraint is based on the evaluation of the 2nd harmonic present in the inrush current. Upon delivery
from the factory, a ratio
I
2f
/
I
f
of 15 % is set. Under normal circumstances, this setting will not need to be
changed. The setting value is identical for all phases and ground. However, the component required for re-
straint may be adjusted to system conditions in address
2202
2nd HARMONIC
. To provide more restraint in
exceptional cases, where energizing conditions are particularly unfavorable, a smaller value can be set in the
aforementioned address, e.g. 12 %. Irrespective of parameter
2202
2nd HARMONIC
, rush blocking will only
occur if the absolute value of the 2nd harmonic is at least 0.025 * I
Nom,sec
.
The effective duration of the cross-blocking
2203
CROSS BLK TIMER
can be set to a value between 0 s (har-
monic restraint active for each phase individually) and a maximum of 180 s (harmonic restraint of a phase
blocks also the other phases for the specified duration).
If the current exceeds the value set in address
2205
I Max
, no further restraint will take place for the 2nd har-
monic.
Manual Close Mode (phases,ground)
When a circuit breaker is closed onto a faulted line, a high-speed trip by the circuit breaker is usually desired.
For overcurrent or high-set element the delay may be bypassed via a Manual Close pulse, thus resulting in
instantaneous tripping. This pulse is prolonged by at least 300 ms. To enable the device to react properly on
occurrence of a fault in the phase elements, address
1213
MANUAL CLOSE
has to be set accordingly. Corre-
spondingly, address
1313
MANUAL CLOSE
is considered for the ground path address. Thus, the user deter-
mines for both elements, the phase and the ground element, what pickup value is active with what delay when
the circuit breaker is closed manually.
External Control Command
If the manual close signal is not sent from 7SJ62/64 device, i.e. neither via the built-in operator interface nor
via a serial interface, but directly from a control acknowledgment switch, this signal must be passed to a
7SJ62/64 binary input, and configured accordingly (
„>Manual Close“
), so that the element selected for
MANUAL CLOSE
can become effective. The alternative
Inactive
means that all elements operate as per con-
figuration even with manual close and do not get special treatment.
Internal Control Function
If the manual close signal is sent via the internal control function of the device, an internal connection of infor-
mation has to be established via CFC (interlocking task level) using the CMD_Information block (see Figure 2-
19).
Figure 2-19
Example for the generation of a manual close signal using the internal control function
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