Functions
2.3 Directional Overcurrent Protection Ground 67, 67N
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
98
Setting the parameters for direction determination
Parameter 1617 67N POLARIZAT. can be set to specify whether direction determination is accomplished
from the zero sequence quantities, the ground quantities (with VN and IN) or the negative sequence quan-
tities (with V2 and I2) in the ground directional element. The first option is the preferential setting; the latter
is selected if there is a risk of the zero voltage becoming too small due to unfavorable zero impedance or a
parallel line influencing the zero sequence system.
Note
If parameter 213 VT Connect. 3ph is set to Vab, Vbc or Vab, Vbc, Vx, the direction is always determined
using the negative sequence values V2/I2. For these voltage connection types the zero sequence voltage VN
or 3V0) is not available.
High-current elements 67N-2, 67N-3 directional
The high-current elements 67N-2 PICKUP or 67N-3 PICKUP are set at address 1602 or 1628 and the as-
sociated delays 67N-2 DELAY or 67N-3 DELAY at 1603 or 1629. The same considerations apply for these
settings as for the phase currents.
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 directional 67N-2 Element or 67N-3 Element is not required, set the pickup threshold 67N-
2 PICKUP or 67N-3 PICKUP to ∞. This setting prevents tripping and the generation of a pickup indication.
67N-1 Directional overcurrent element
The setting of the overcurrent element 1604 67N-1 PICKUP is mainly determined by the minimum anticipated
ground fault current.
If the relay is used to protect transformers or motors with large inrush currents, the inrush restraint feature of
7SK80 may be used for the 67N-1 PICKUP element (for more information see margin heading "Inrush Re-
straint").
The delay is set at address 1605 67N-1 DELAY and should be based on system coordination requirements
for directional tripping. For ground currents in a grounded system a separate coordination chart with short time
delays is often used.
The selected time is an additional time delay 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 67N-1 Element is not required at all, the pickup value 67N-1 PICKUP should be set to ∞.
This setting prevents tripping and the generation of a pickup message.
Pickup stabilization (67N Ground)
Pickup of the directional overcurrent elements can also be stabilized using configurable dropout times under
address 1618 67N T DROP-OUT.
67N-TOC Directional overcurrent element with IEC and ANSI curves (inverse-time, Ground)
Having set address 116 67N/67N-TOC = TOC IEC when configuring the protection functions (Section 2.1.1),
the parameters for the inverse time characteristics will also be available. Specify in address 1611 67N-TOC
IEC the desired IEC Curve (Normal Inverse, Very Inverse, Extremely Inv. or
Long Inverse). If
address 116 67N/67N-TOC = TOC ANSI, you can select the desired ANSI–Curve (Very Inverse, Inverse,
Short Inverse, Long Inverse, Moderately Inv., Extremely Inv. or Definite Inv.) in address
1612 67N-TOC ANSI.
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