ABB RELION REF615R, Technical Manual

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Figure 123: 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 123 . For the excitation level of 1.4, the second dot in Figure 123 , the
curve "OvExt IDMT Crv2" gives 260 milliseconds as per Equation 5 , but the Minimum
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%,
1MRS240050-IB C
Section 4
Protection functions
REF615R 259
Technical Manual