ABB Relion 620 Series - Page 1155

Figure 619: Operate time curve based on IDMT characteristic with Minimum operate
time set to 1 second
11.3.1.1 Standard inverse-time characteristics for overvoltage protection
The operate times for the standard overvoltage IDMT curves are defined with the
coefficients A, B, C, D and E.
The inverse operate time can be calculated with the formula:
t s
k A
B
U U
U
C
D
E






=
⋅
×
− >
>
−






+
(Equation 201)
1MRS757644 H
General function block features
620 series
Technical Manual
1155