Hysteresis - DEMA 400 Series User Manual

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).
4.3.3.4.5

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 neutral overvoltage protection start value is set to 100 V, the hysteresis value
is set to 5%, the protection is activated when the protection exceeds 105 V; If it falls below 95
V, the protection is deactivated. This hysteresis value can be selected from 1% to 20%.
4.3.4 Frequency Protection Settings
Voltage Protection Settings can be selected from Menu> Protection Settings> Frequency
Protection Settings
Relay protection of the line / motor frequency protection briefly; It operates according to the
principle of deactivating the protected part by comparing the frequency information of voltage
to the relay with the frequency information of voltage assigned in the protection functions.
The function symbols on the device setting screen are shown according to IEC 61850, IEC
60617 and IEEE ANSI standards. The function symbol selection according to these standards
is as follows: Main Menu> System Settings> Function Symbol
• ANSI 81U - Low Frequency Protection
• ANSI 81O - Over Frequency Protection
• ANSI 81R - Frequency Change Rate Protection
Voltage protection settings menu device screen is as follows.
Frequency Protection Settings Display
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