Figure 380: Example of how the inverse time characteristic is leveled out with
currents over 50 x In and the Setting Start value setting “2.5 x In”. (the IDMT Sat
point setting is set to maximum and the Minimum operate time setting is set to
minimum).
The grey zone in
Figure 380
shows the behavior of the curve in case the measured
current is outside the guaranteed measuring range. Also, the maximum measured
current of 50 x In gives the leveling-out point 50/2.5 = 20 x I/I>.
11.2.1.1 Standard inverse-time characteristics
For inverse-time operation, both IEC and ANSI/IEEE standardized inverse-time
characteristics are supported.
The operate times for the ANSI and IEC IDMT curves are defined with the
coefficients A, B and C.
The values of the coefficients can be calculated according to the formula:
1MRS758755 C
General function block features
REC615 & RER615
Technical Manual
747
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