1MAC309294-MB F Section 4
Protection functions
RER620 149
Technical Manual
4.1.4.7 Timer characteristics
67/51N and 67/50N supports both DT and IDMT characteristics. The user can select the
timer characteristics with the Operating curve type setting.
The relay provides 16 IDMT characteristics curves, of which seven comply with the IEEE
C37.112 and six with the IEC 60255-3 standard. Two curves follow the special
characteristics of ABB praxis and are referred to as RI and RD. In addition to this, a user
programmable curve can be used if none of the standard curves are applicable. The user
can choose the DT characteristic by selecting the Operating curve type values “ANSI Def.
Time” or “IEC Def. Time”. The functionality is identical in both cases.
The following characteristics, which comply with the list in the IEC 61850-7-4
specification, indicate the characteristics supported by different stages:
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