ABB 615 series Technical Manual page 660

Section 4
Protection functions
654
GUID-433F1AF8-DA0B-4FEA-A281-1872487F3B97 V1 EN
Figure 325: Tripping curve of "OvExt IDMT Crv2" based on the settings specified in
example 3. The two dots marked on the curve are referred to in the text.
If the excitation level stays at 1.26, the tripping occurs after 26.364 s as per the marked dot
in Figure 325. For the excitation level of 1.4, the second dot in
"OvExt IDMT Crv2" gives 0.2636 s as per Equation, but the Minimum trip time setting
limits the trip time to 1.0 s.
The Maximum trip time setting limits the trip time to 1000 s if the
excitation level stays between 1.1 and 1.16.
In general, however, the excitation level seldom remains constant.
Therefore, the exact trip times in any inverse time mode are difficult to
predict.
Example 4
In this case, the function operation is according to IDMT. The Operating curve type
setting is selected as "OvExt IDMT Crv4". The corresponding example settings for the
1MAC059074-MB A
Figure 325, the curve
615 series ANSI
Technical Manual