Functions
2.4 Backup Overcurrent
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
80
Definite Time Overcurrent Element
50-3
The
50-3
element operates independently of the other elements. Its logic corresponds to the
50-1
and
50-2
el-
ements described above, but operates non-directional only.
If parameter
50-STUB Inrush
(address
2653
) is set to
YES
, the element is blocked.
Figure 2-27
Logic diagram of the
50-3
element
Inverse Time Overcurrent Element
51
The logic of the inverse overcurrent element basically operates in the same way as the other elements. The
time delay, however, is calculated based on the type of the set characteristic, the intensity of the current and a
time multiplier (following figure). A pre-selection of the available characteristics was already carried out during
the configuration of the protection functions. Furthermore, an additional constant time delay
51-B AddT-
DELAY
or
51N-B AddTdelay
may be selected which is added to the inverse time. The possible characteristics
are shown in the Technical Data.