Hysteresis - DEMA 400 Series User Manual

According to the menu settings, exceeding 45Hz and without breaker tripping, It was selected
to count the DMT (constant time) reset time (0.04 s) when the frequency does not fall below
45Hz In. Thus, after the current falls below the threshold, 40 ms will be counted. If the
threshold is not exceeded until the end of this period, the protection function trip time counter
will be reseted. Reset delay thresholds are in the range of (0-60).
4.3.4.1.5

Hysteresis

It allows the selection of the minimum and maximum values for the protection to be activated
by entering value in percentages and the same value being switched off in percentage. For
example, if the Under Frequency Protection start value is set to 45Hz, the hysteresis value is
set to 5%, Protection is active when it falls under 45hz; protecton is disactive when it exceeds
47.5hz. This hysteresis value can be selected from 1% to 20%.
81O – Over Frequency Protection
4.3.4.2
The overvoltage protection settings are located Menu> Protection Settings> Frequency
Protection Settings> Over Frequency Protection
Working principle; The measured frequency value is the activation of the protection when the
assigned protection exceeds the threshold. The time characteristic is DMT (constant time)
characteristic.
Directional phase overcurrent protection is indicated by f f>, f>>, f>>>, f>>>>, f>>>>>,
f>>>>>> in IEC 60617 Standards; by PIOF_1, PIOF_2, PIOF_3, PIOF_4, PIOF_5 ve
PIOF_6 in IEC 61850 ; 81-O-1, 81-O-2, 81-O-3, 81-O-4, 81-O-5 ve 81-O-6 in IEEE/ANSI
Standards
EŞİK-1 PIOF_1
EŞİK-2 PIOF_2
EŞİK-3 PIOF_3
EŞİK-4 PIOF_4
EŞİK-5 PIOF_5
EŞİK-6 PIOF_6
Over Frequency Protection
IEC 61850
Over Frequency Protection Function Symbols
IEC 60617 IEEE-ANSI
f> 81U-I-1
f>> 81U-I-2
f>>> 81U-I-3
f>>>> 81U-I-4
f>>>>> 81U-I-5
f>>>>>> 81U-I-6
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