[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