Functions
2.4 Backup Overcurrent
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
84
Figure 2-29
Directional characteristic of the time overcurrent protection
Definite Time Overcurrent Element
67-1
The directional overcurrent elements basically work in the same way as the non-directional elements. Pickup,
however, depends on the result of the direction determination. The direction determination is accomplished
using the measured quantities and the corresponding directional characteristics.
67-B2 PICKUP
is used as setting values for the phase current;
67N-B2 PICKUP
is used for the ground cur-
rent. A trip command is issued after pickup of an element and expiration of the associated time delays
67-B2
DELAY
or
67N-B2 DELAY
. The dropout value is approximately 7% below the pickup value, but at least 1.8%
of the nominal current, below the pickup value.
Figure 2-30 shows the logic diagram of the
67-1
elements. They can be blocked via the binary input . Addition-
ally, the ground current element can be blocked separately via the binary input
„>BLOCK 67N-TOC“
.
The binary input
„>5X-B InstTRIP“
and the evaluation of the indication „switch“ (onto fault) can act sepa-
rately on the directional phase and/or ground element.
Parameter
67(N)-B2 Pil/BI
(address
2628
) determines whether a non-delayed trip of this element via
binary input
„>5X-B InstTRIP“
is possible (
YES
) or impossible (
NO
). This parameter is also used for instan-
taneous tripping before automatic reclosing.
The indications or are created from the individual directional indications ( to ) determined specifically for the
phase or current if a valid direction was determined for a phase or ground current (forward or reverse). These
indications can then be transmitted to another device where they can cause instantaneous tripping there if an
overcurrent element of the receiving device has picked up, too. The indications must be linked via CFC to this
end.