ABB Relion Technical Manual page 744

Section 21
Time inverse characteristics
738
For the IEC curves there is also a setting of the minimum time-lag of operation, see
figure 319.
Operate
time
tMin
IMin
IEC05000133 V2 EN
Figure 319: 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 121:
1MRK 502 048-UUS A
Current
IEC05000133-3-en.vsd
Technical manual