ABB RELION 620 Series Technical Manual page 309

1MAC504801-IB E
620 series ANSI
Technical Manual
Table 250: Parameters a, b and c for different IDMT curves
Operating curve type
a
setting
OvExt IDMT Crv1 2.5
OvExt IDMT Crv2 2.5
OvExt IDMT Crv3 2.5
GUID-BD1205DC-1794-4F64-A950-6199C54DB7B1 V1 EN
Figure 137: Trip time curves for the overexcitation IDMT curve ("OvExt IDMT Crv1")
for parameters a = 2.5, b = 115.0 and c = 4.886
Overexcitation IDMT curve 4
The base equation for the IDMT curve "OvExt IDMT Crv4" is:
Protection functions
b c
115.00 4.886
113.50 3.040
108.75 2.443
Section 4
303