ABB RELION REX640 Technical Manual page 819

1MRS759142 C
REX640
Technical Manual
GUID-89605736-9D42-4D40-8D61-6E69ACA20620 V1 EN
Figure 441: 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 26.364 s as per the
marked dot in Figure 441. For the excitation level of 1.4, the second dot in
the curve "OvExt IDMT Crv2" gives 0.2636 s as per
operate time setting limits the operate time to 1.0 s.
The Maximum operate time setting limits the operate 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 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 = 3600 s, Constant delay = 0.8 s
and Cooling time = 100 s.
Section 4
Protection functions
Figure
Equation 203, but the Minimum
441,
813