Iskra FPC 200 - Positive Sequence Undervoltage Protection - ANSI Code 27 D

Functionality
38 USER MANUAL FPC 200 - 3/2017
Positive sequence undervoltage protection - ANSI code 27D
Positive sequence undervoltage protection is a function that protects the feeder or other elements of the power system
from wrong phase direction and low positive sequence of three phase system.
2.3.4.1 Functionality
Undervoltage protection is single analog input function,
used as time delayed protection. It picks up when
positive sequence voltage U
1
drops below the selected
threshold. The function can be enabled or disabled
through corresponding menu.
Several protection instances with different settings can
run independently at the same time.
The selection of pickup value, pickup delay as well as
drop-out ratio and drop-out delay helps the user to fine
tune the protection according to the project
specifications.
27D U1 Undervoltage
COUNTERS
0
Enabled:
1A 1B 2A 2B
No
Pickup:
Pickup value: 0,75xUn
Trip delay:
1,5s
0
Trip:
CONTROL SETTINGS
Pickup delay:
5ms
Drop-out delay:
0,2s
0,95 Drop-out ratio:
BLOCK SETTINGS
Input: none
Fuse failure: Yes
Figure 2.28: Positive sequence undervoltage protection setting
as seen on HMI.
2.3.4.2 Delays
Function includes following delays explained in Chapter
2.1:
 Pickup delay
 Trip delay
 Drop-out delay
2.3.4.3 Block settings
Pickup of any instance separately of protection can be
individually blocked by:
 Any user defined signal [2.6.5].
 Enabling Fuse failure protection [2.6.4].
In addition the protection is blocked when voltage drops
below 40 % of U
n
. To ensure the correct function of the
protection, the protection block is time delayed for a
brief moment after any condition for blocking has
expired. The individual protection trip exhibits pulse
type if connected to trip relay [4.2.4.5.7, relay mapping
section], to ensure correct CBFP [2.6.1.10] functionality.