ABB RELION REX640 Technical Manual page 896

Protection functions
Figure 500: 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 500
in
249
Example 4
In this case, the function operation is according to IDMT. The
curve type setting is selected as "OvExt IDMT Crv4". The corresponding
example settings for the IDMT curve operation are given as:
110%,
= 3600 s,
896
Figure 500
, the curve "OvExt IDMT Crv2" gives 0.2636 s as per
Minimum operate time setting limits the operate time to 1.0 s.
, but the
Maximum operate time setting limits the operate
The
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.
Voltage Max Cont = 100%, Time multiplier = 5, Maximum operate time
Constant delay = 0.8 s and Cooling time = 100 s.
. For the excitation level of 1.4, the second dot
1MRS759142 F
Equation
Operating
Start value =
REX640
Technical Manual