ABB RES670 Technical Manual page 891

1MRK 511 408-UUS A
Phasor measurement unit RES670 2.2 ANSI
Technical manual
Operate
time
tMin
IMin
IEC05000133 V2 EN-US
Figure 346: 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 91:
æ
ç
td
[ ]
ç
s
=
t
Pickupn
ç
ç
- ×
0.339 0.235
è
EQUATION1647 V1 EN-US
where:
Pickupn is the set pickup current for step n
td is set time multiplier for step n
i is the measured current
IEC05000133-3-en.vsd
ö
÷
÷
÷
÷
ø
i
Section 26
Inverse time characteristics
Current
(Equation 91)
885