Load encroachment characteristic
ArgLd
ArgLd
ArgLd
ArgLd
RLd
-RLd
jX
R
IEC11000304_1_en
IEC11000304 V1 EN
Figure 154:
Load encroachment characteristics
7.10.7.5
Under voltage seal-in
The under voltage seal-in logic ensures the trip under fault condition, where as under
impedance function will reset due to CT saturation. The start signal of zone 2 and zone
3 elements trigger the under voltage seal-in. This can be selected using the setting
OpModeU<
. The setting
OpModeU<
can be selected as
Off
or
Z2Start
or
Z3Start
.
Select
Z2Start
to choose zone 2 for triggering the seal-in logic. Similarly, select
Z3Start
to choose zone 3 for triggering the seal-in logic.
Under voltage seal-in is activated from the criterion based on line-to-line voltage
magnitude. The voltage criteria checks by comparing all three line-to-line voltage
levels with the level given by the setting parameter
U<
. If any loop detects lower
voltage, the under voltage seal-in logic gets triggered, provided the respective selected
zone start is also high. Once the under voltage seal-in logic is triggered, the pick-up
signal STUV becomes high. If it is constantly high for a time longer than the setting
tU<
, the tripping signal TRUV is issued as a pulse signal with a duration of one
second.
Figure
shows the functionality of under voltage seal-in for zone 2 and zone 3.
1MRK502052-UEN B
Section 7
Impedance protection
331
Technical manual
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