Siemens SIPROTEC 4 7SD80 Manual page 80

Functions
2.4 Backup overcurrent
B1 DELAY or 50N-B1 DELAY. The dropout value is approximately 7% below the pickup value, but at least
1.8% of the nominal current.
Figure 2-30 shows the logic diagram of the 67-1 elements. The same applies analogously to the high-set
current element 67-2
Inverse Time Overcurrent Element 67-TOC
The logic of the inverse overcurrent element basically operates in the same way as that of the non-directional
element. Pickup, however, depends on the result of the direction determination. The direction determination
is accomplished using the measured quantities and the corresponding directional characteristics.
The time delay, however, is calculated based on the type of the set characteristic, the intensity of the current
and the time factor 67-TOC TD ANSI or 67N-TOC TD ANSI. Furthermore, an additional constant time
delay 67-TOC AddTDel. or 67N-TOC AddTDel may be selected which is added to the inverse time. The
possible characteristics are shown in the Technical Data.
The indications
(7257 to 7264) determined for the phase and ground current provided that a valid directional result (forward
or reverse) was determined for the phase or ground current. These indications can then be transmitted to
another device where they can cause instantaneous tripping if an overcurrent element of the received device
has picked up, too. The indications must be linked via CFC to this end.
The following figure shows the logic diagram of the directional 67-TOC element. The setting addresses for the
IEC characteristics are shown by way of example. In the setting notes (Section
different setting addresses are described in detail.
The non-directional and the directional inverse time overcurrent element 51 always uses the same character-
istic curve that is parameterized via 2642 (IEC) or 2643 (ANSI). Different inverse times and additional times
can be parameterized here.
80
67(N) forward or 67(N) reverse are created from the individual directional indications
2.4.4 Setting Notes), the
SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018