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) frequency is above 45Hz. 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).
4.3.4.2.5

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 60Hz, the hysteresis value is
set to 5%, Protection is active when it exceeds 60hz; protecton is disactive when it exceeds
%63. This hysteresis value can be selected from 1% to 20%.
81R – Rate of Change of Frequency Protection
4.3.4.3
The overvoltage protection settings are located Menu> Protection Settings> Frequency
Protection Settings> Rate of Change of Frequency Protection
Working principle; The change in measured frequency value is the activation of the protection
when the set frequency change exceeds or falls below the threshold values. The time
characteristic is DMT (constant time) characteristic.
Directional phase overcurrent protection is indicated by (df/dt)>, (df/dt)>>, (df/dt)>>>,
(df/dt)>>>>, (df/dt)>>>>> , (df/dt)>>>>>>in IEC 60617 Standards; Standartlarında PIOF_1,
PIOF_2, PIOF_3, PIOF_4, PIOF_5 ve PIOF_6 in IEC 61850; 81R-I-1, 81R-I-2, 81R-I-3,
81R-I-4, 81R-I-5 ve 81R-I-6 in IEEE/ANSI Standards
Rate of Change of Frequency Protection
IEC 61850 IEC 60617
89
IEEE-ANSI