ABB RELION REX640 Technical Manual page 623

1MRS759142 F
Consider next the following example with Operating curve type = "Inverse time
IEEE80":
Example 6. Inverse time operation of IFPTOC, when
voltage based",
multiplier = 500 is illustrated in
(setting
maximum operate time of 5000 ms (settings
Max Op Tm ). Maximum earthing resistance value encountered in the protected
feeder is set to be 10 ohms (setting
= 1. For illustrating the operating speed requirement of protection, limits of earth
potential rise durations defined in Finnish national Electrical Safety Regulations 89
are shown for reference.
REX640
Technical Manual
Reduction factor considers the fact that only part of the earth-
Setting
fault current (I ) will flow back through "remote" earth and introduces
F
earth potential rise and touch voltages.
Operating curve type = "Inverse time IEEE80" is selected, then
When
UTp multiplier is not effective.
setting
Operating curve type = "Inverse time IEEE80" and setting IEEE
Touch Vol Str Val ). IFPTOC is set to have minimum operate time 100 ms and
Operation principle = "Touch
Figure 354
. Start value for operation is set to be 20 V
IDMT stage Min Op Tm, IDMT stage
Maximum earthing Ris ) and Reduction factor
Protection functions
623