For the IEC curves there is also a setting of the minimum time-lag of operation, see
figure 179.
IEC05000133-3-en.vsd
tMin
Current
Operate
time
IMin
IEC05000133 V2 EN
Figure 179: Minimum time-lag operation for the IEC curves
In order to fully comply with IEC curves definition setting parameter tMin shall be set
to the value which is equal to the operating time of the selected IEC inverse time curve
for measured current of twenty times the set current pickup value. Note that the
operating time value is dependent on the selected setting value for time multiplier k.
In addition to the ANSI and IEC standardized characteristics, there are also two
additional inverse curves available; the RI curve and the RD curve.
The RI inverse time curve emulates the characteristic of the electromechanical ASEA
relay RI. The curve is described by equation
77:
Section 19 1MRK 505 277-UUS C
Time inverse characteristics
464
Technical Manual
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