ABB RELION 620 Series Technical Manual page 688

Section 4
Protection functions
682
GUID-433F1AF8-DA0B-4FEA-A281-1872487F3B97 V1 EN
Figure 345: Operating 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 operation occurs after 26360 milliseconds as
per the marked dot in Figure
Figure 345, the curve "OvExt IDMT Crv2" gives 260 milliseconds as per Equation,
but the Minimum operate time setting limits the operate time to 1000 milliseconds.
The Maximum operate time setting limits the operate time to 1000000 milliseconds if
the excitation level stays between 1.1 and 1.16.
In general, however, the excitation level seldom remains constant.
Therefore, the exact operate 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 IDMT curve operation are given as: Start value = 110%, Voltage Max Cont =
100%, Time multiplier = 5, Maximum operate time = 3600000 milliseconds and
Constant delay = 800 milliseconds.
345. For the excitation level of 1.4, the second dot in
1MRS757644 F
620 series
Technical Manual