Siemens SIPROTEC 7SJ61 Manual page 70

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
Figure 2-15
Inrush Restraint
When applying the protection device to transformers where high inrush currents are to be expected, the 7SJ61
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
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
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.
70
Entry and visualization of a user-defined tripping characteristic in Digsi — example
/I of 15 % is set. Under normal circumstances, this setting will not need to be
2f f
.
Nom,sec
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008