Functions
2.4 Backup Overcurrent
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
86
Definite Time High-set Element
67-2
The directional overcurrent element basically works in the same way as 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.
67-B1 PICKUP
is used as setting values for the phase current;
67N-B1 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-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, below the pickup value.
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 or are created from the individual directional indications ( to ) 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 instanta-
neous 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 2.4.4), the different setting ad-
dresses 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.