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Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
50-1 Element (phases)
For setting the 50-1 element, the maximum anticipated load current must be considered. Pickup due to over-
load must never occur since in this mode, the device operates as fault protection with correspondingly short
tripping times and not as overload protection. For this reason, lines are set to approx. 20 % above the maximum
expected (over)load and transformers to approx. 40 %.
The settable time delay (address 1205 50-1 DELAY) results from the grading coordination chart defined for
the system.
The selected time is an additional delay time and does not include the operating time (measuring time, dropout
time). The delay can also be set to ∞. In this case, the Element will not trip after pickup. However, pickup, will
be signaled. If the 50-1 Element is not required at all, then the pickup threshold 50-1 should be set to ∞. This
setting prevents tripping and the generation of a pickup message.
50N-1 Element (ground)
The 50N-1 element is normally set based on minimum ground fault current.
If you expect large inrush currents when using the protection device on transformers, the inrush restraint
feature of 7SC80 may be used for the 50N-1 element. It can be enabled or disabled for both the phase current
and the ground current at address 2201 INRUSH REST.. The characteristic values of the inrush restraint are
listed in subsection "Inrush Restraint".
The settable delay time (address 1305 50N-1 DELAY) results from the time coordination chart defined for the
system. For ground currents in a grounded system a separate coordination timer with short time delays can be
applied.
The selected time is an additional delay time and does not include the operating time (measuring time, dropout
time). The delay can also be set to ∞. In this case, the Element will not trip after pickup. However, pickup, will
be signaled. If the 50N-1 Element is not required at all, the pickup threshold 50N-1 PICKUP should be set to
∞. This setting prevents tripping and the generation of a pickup message.
Pickup Stabilization (Definite Time)
The configurable dropout times 1215 50 T DROP-OUT or 1315 50N T DROP-OUT can be set to implement
a uniform dropout behavior when using electromechanical relays. This is necessary for a time grading. The
dropout time of the electromechanical relay must be known to this end. Subtract the dropout time of the device
(see Technical Data) from this value and enter the result in the parameters.
Inrush Restraint
When applying the protection device to transformers where high inrush currents are to be expected, the 7SC80
can make use of an inrush restraint function for the overcurrent elements 50–1, 51, 50N-1 and 51N.
Inrush restraint is only effective and accessible if address 122 InrushRestraint was set to Enabled during
configuration. If this function is not required, then Disabled is set. At address 2201 INRUSH REST., the func-
tion is switched ON or OFF jointly for the overcurrent elements 50-1 PICKUP and 50N-1 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).
66
/I
of 15 % is set. Under normal circumstances, this setting will not need to be
2f
f
.
Nom,sec
SIPROTEC, 7SC80, Manual
E50417-G1140-C486-A1, Release date 12.2011
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