ABB RELION 620 Series Technical Manual page 315

1MAC504801-IB E
620 series ANSI
Technical Manual
GUID-433F1AF8-DA0B-4FEA-A281-1872487F3B97 V1 EN
Figure 140: 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 26360 milliseconds as per the
marked dot in Figure 140. For the excitation level of 1.4, the second dot in
curve "OvExt IDMT Crv2" gives 260 milliseconds as per
trip time setting limits the trip time to 1000 milliseconds. The Maximum trip time setting
limits the trip 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 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
IDMT curve operation are given as: Pickup value = 110%, Voltage Max Cont = 100%,
Section 4
Protection functions
Figure 140, the
Equation 10, but the Minimum
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