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Section 4
1MAC050144-MB C
Protection functions
124
615 series ANSI
Technical Manual
4.1.1.12
Technical revision history
Table 107: 50P–3 Technical revision history
Table 108: 50P–1/2 Technical revision history
Table 109: 51P Technical revision history
4.1.2
Three-phase non-directional long-time overcurrent protection
51LT
4.1.2.1
Identification
4.1.2.2
Function block
Figure 50:
Function block
4.1.2.3
Functionality
The three-phase long-time overcurrent protection 51LT is used as one-phase, two-phase
or three-phase non-directional overcurrent and short-circuit protection for feeders.
The operation of this function is very similar to the 51P function except that inverse curves
operating times are 10 times that of 51P.
The function also contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
Technical revision
Change
C
Minimum and default values changed to 20 ms for
the
Trip delay time
setting.
Minimum value changed to 1.00 x I
n
for the
Pickup
value
setting.
Technical revision
Change
C
Measurement mode
"P-to-P + backup" replaced
with "Peak-to-Peak"
Technical revision
Change
B
Minimum and default values changed to 40 ms for
the
Trip delay time
setting
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Three-phase non-directional long
time overcurrent protection
PHLTPTOC
3I>
51LT
Содержание 615 Series ANSI
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