[dw_7SR5_function51ApplicationAndSettingNotes, 1, en_US]
Settings Example
The 51-n characteristic element provides a number of 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 and a number of manufacturer specific
curves are supported.
IDMTL characteristics are defined as Inverse because their tripping times are inversely proportional to the
fault current being measured. This makes them particularly suitable to grading studies where it is important
that only the relay(s) closest to the fault operate. Discrimination can be achieved with minimized operating
times.
To optimize the grading capability of the relay additional time multiplier, Follower DTL or Minimum
Operate Time settings can be applied.
[dw_7SR5_IECcurve withTm&followerDTL, 1, en_US]
Figure 5-21
IEC NI Curve with Time Multiplier and Follower DTL Applied
Protection and Automation Functions
5.14 51 Time-Delayed Overcurrent – Phase
Reyrolle 7SR5, Transformer Protection Device, Device Manual 237
C53000-G7040-C015-1, Edition 11.2019
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