ABB REG650 Technical Manual page 642

Section 21
Time inverse characteristics
636
For the IEC curves there is also a setting of the minimum time-lag of operation, see
figure 266.
Operate
time
tMin
IMin
IEC05000133 V2 EN
Figure 266: 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 118:
1MRK 502 043-UUS B
Current
IEC05000133-3-en.vsd
Technical Manual