ABB 615 Series ANSI, Technical Manual

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1MAC050144-MB C
Section 4
Protection functions
615 series ANSI 127
Technical Manual
blocked and the timers are reset. In the "Block TRIP output" mode, the function operates
normally but the
TRIP
output is not activated.
4.1.2.5 Timer characteristics
51LT 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 relay provides 9 IDMT characteristics curves, of which seven comply with the IEEE
C37.112 and two with the IEC 60255-3 standard. 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 value "Long Definite Time".
Table 110: Timer characteristics supported
Table 111: Reset time characteristics supported by different stages
4.1.2.6 Application
The long time overcurrent protection is used in special feeder protection application where
operating time provided by 51P is not good enough for coordination purpose.
Operating curve type 51LT
(1) Long Time Extremely Inverse x
(2) Long Time Very Inverse x
(3) Long Time Inverse x
(4) Long Time Moderately Inverse x
(5) Long Definite Time x
(6) Very Long Time Extremely Inverse x
(7) Very Long Time Very Inverse x
(8) Very Long Time Inverse x
(9) Long Time Normal Inverse x
(14) IEC Long Time Inverse x
(17) Prorammable x
For a detailed description of timers, refer to section General function block
features in this manual.
Reset curve type 51LT
(1) Intermediate x
(2) Def time reset x
(3) Inverse reset x