mode which selects the blocking mode. The BLOCK input can be controlled by a binary
input, a horizontal communication input or an internal signal of the protection relay's
program. The influence of the BLOCK signal activation is preselected with the global
setting Blocking mode.
The Blocking mode setting has three blocking methods. In the "Freeze timers" mode, the
operation timer is frozen to the prevailing value, but the TRIP output is not deactivated
when blocking is activated. In the "Block all" mode, the whole function is blocked and the
timers are reset. In the "Block TRIP output" mode, the function operates normally but the
TRIP output is not activated.
4.2.1.5 Measurement modes
The function operates on three alternative measurement modes: "RMS", "DFT" and
"Peak-to-Peak". The measurement mode is selected with the Measurement mode setting.
Table 318: Measurement modes supported by 51N/50N or 51G/50G stages
Measurement mode 51N, 51G 50N, 50G 50N-3, 50G-3
RMS x x
DFT x x
Peak-to-Peak x x x
For a detailed description of the measurement modes, see the
Measurement modes section in this manual.
4.2.1.6 Timer characteristics
51N, 51G, 50N, 50G supports both DT and IDMT characteristics. The user can select the
timer characteristics with the Operating curve type and Type of reset curve settings. When
the DT characteristic is selected, it is only affected by the Trip delay time and Reset delay
time settings.
The protection 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:
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 317
Technical Manual
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