Time-Delayed Overcurrent (51/51N)
The time-delayed overcurrent characteristic element provides several time/current operate characteristics. The
element can be defined as either an Inverse Definite Minimum Time Lag (IDMTL) or Definite Time Lag (DTL)
characteristic. If an IDMTL characteristic is required, then IEC, ANSI/IEEE curves are supported.
The IDMTL characteristics are defined as Inverse because the tripping times are inversely proportional to the
fault current being measured. This is suitable for grading studies and important in operating the relay which is
close to the fault. Discrimination can be achieved with minimized operating time.
To optimize the grading capability of the relay extra time multiplier, Follower DTL or Minimum operate time
settings can be applied.
[dw_IEC-NI-curve_with_time-muliplier_followe-DTL, 1, en_US]
Figure 5-2
IEC NI Curve with Time Multiplier and Follower DTL Applied
5.3
Applications
5.3 Time-Delayed Overcurrent (51/51N)
74 Reyrolle, 7SR46 Device, Manual
C53000-G7040-C103-1, Edition 10.2022
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