Figure 348: Example of definite time operation of IFPTOC, when Operation principle
= “Touch voltage based”, Operating curve type = “Definite time”. Setting Touch Vol
Str Val = 40 V and DT stage Op time = 400 ms. Maximum earthing Ris = 10 ohm
Parameter defining maximum earthing resistance, setting
Maximum
earthing Ris
must be always set in case
Operation principle
= “Touch
voltage based” and
Operating curve type
= “Definite time” is selected.
Setting
Maximum earthing Ris
is needed to scale the estimated earth-
fault current value into corresponding touch voltage or earth potential
rise value.
When
Operating curve type
= “Inverse time EN50522” is selected, then
• Operate time is inverse time according to standard EN50522:
1MRS759142 F
Protection functions
REX640
Technical Manual
613
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