re_620_tech_757644_enb 447
Post on 30-Sep-2015
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When the reset period is initiated, the time for which START has been active issaved. If the fault reoccurs, that is, the negative-sequence current rises above theset value during the reset period, the operate calculations are continued using thesaved values. If the reset period elapses without a fault being detected, the operatetimer is reset and the saved values of start time and integration are cleared.
Inv. curve BThe inverse time equation for curve type B is:
t sk
I
I
I
Ir
S
r
[ ] =
2
2 2
GUID-805DCB50-71D2-4721-830B-3343E1A5500B V1 EN (Equation 68)
t[s] Operate time in seconds
k Machine time Mult
I2 Negative-sequence current
IS Set Start value
Ir Set Rated current
1MRS757644 B Section 4Protection functions
620 series 441Technical Manual
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