Siemens SIPROTEC 7SD610 Manual page 109

Directional inverse time overcurrent stage I
The logic of the inverse overcurrent stage also operates chiefly in the same way as that of the non-directional
stage. However, pickup is dependent on the result of the direction determination. Direction determination
occurs via the measuring values and the respective directional characteristics.
However, the time delay is calculated here based on the type of the set characteristic, the intensity of the
current and a time multiplier D Ip Dir. or D 3I0p Dir.. Furthermore, an additional constant time delay T
Ip Add Dir. or T 3I0p Add Dir. may be selected, which is added to the inverse time. The possible char-
acteristics are shown in the Technical Data.
The individual phase or earth specific directional indications (7240 to 7247) are used to generate the indications
„O/C Dir.forward" or „O/C Dir.reverse" if a valid direction result (forward or backward) was deter-
mined for a phase or earth current. These messages can then be transferred to a different device and there
they can cause an immediate trip if an overcurrent stage of the receiving device has also picked up. The indi-
cations must then be combined via CFC (OR function).
The following figure shows the logic diagram of the directional I
of the IEC characteristics are shown by way of an example. In the setting information (Section 2.9.3) the differ-
ent setting addresses are elaborated upon.
The directional and the non-directional inverse overcurrent stageI
eterized via the parameter2660 (IEC) or 2661 (ANSI). Various inverse times and additional times can be con-
figured.
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
ger
P
2.9 Backup Time Overcurrent Protection
.ger stages. The setting parameter addresses
P
always uses the same characteristic param-
P
Functions
109