Siemens 7SC80 Manual page 128

Functions
2.3 Directional Overcurrent Protection 67, 67N
NOTE
i
i
If the threshold value of the 67-1 or 67N-1 element is exceeded, the phase-specific directional indications
"forward" or "reverse" are output (indications 2628 to 2636), independent of whether the fault direction is
the same as the configured direction.
These indications are used for directional comparison protection.
Quantity Selection for Direction Determination for the Directional Ground Element
Parameter 1617 67N POLARIZAT. can be set to specify whether direction determination is accomplished
from the zero sequence quantities or ground quantities (with VN and IN) or from the negative sequence
quantities (with V2 and I2) in the ground directional element. The first option is the preferential setting;
the latter is to be selected in case of danger that the zero voltage be too small due to unfavourable zero impe-
dance or that a parallel line influences the zero system.
NOTE
i
i
If parameter 213 VT Connect. 3ph is set to Vab, Vbc, the direction is always determined using the
negative sequence values V2/Ι2. For these voltage connection types, the zero sequence voltage (VN or
3V0) is not available.
Directional High-Set Elements 67-2, 67-3 (Phases)
The high-current elements 67-2 PICKUP or 67-3 PICKUP are set at address 1502 or 1534 respectively, the
associated time delays 67-2 DELAY and 67-3 DELAY at 1503 and 1535 respectively. The same considera-
tions apply to the element settings as for the non-directional time overcurrent protection in Section
2.2.12 Setting Notes.
The selected time is a pure additional delay time and does not include the operating time (measuring time,
dropout time). If the delay time is set to ∞, the element does not trip after the pickup, but the pickup condi-
tion is signaled. If the directional 67-2 element or 67-3 element is not required, set the pickup threshold 67-2
PICKUP or 67-3 PICKUP to ∞. With this setting, no pickup signal or trip is generated.
Directional High-Set Elements 67N-2, 67N-3 (ground)
The high-current element 67N-2 PICKUP or 67N-3 PICKUP is set at address 1602 or 1634. The associated
delay 67N-2 DELAY or 67N-3 DELAY at 1603 or 1635. 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). If the delay time is set to ∞, the element does not trip after the pickup, but the pickup condi-
tion is 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 indica-
tion.
Directional Overcurrent Element 67-1 (phases)
The maximum appearing load current is very important for the setting of the overcurrent element 1504 67-1
PICKUP. Pickup due to overload 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 delay for the directional element (address 1505 67-1 DELAY) is usually set shorter than the delay for
nondirectional element (address 1205) since the non-directional elements overlap the directional elements as
backup protection. It should be based on the system coordination requirements for directional tripping.
For parallel transformers supplied from a single source (see "Applications"), the delay of element 67-1 DELAY
located on the load side of the transformers may be set to 0 without provoking negative impacts on selec-
tivity.
The selected time is only an additional time delay and does not include the operating time (measuring time,
dropout time). The delay can be set to ∞. After pickup the element will then not trip. Pickup, however, will be
128 SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017