Sel 751A - Table 4.11 Neutral Time-Overcurrent Settings; Figure 4.5 Negative-Sequence Time-Overcurrent Element 51 QT

4.13
Date Code 20100129 Instruction Manual SEL-751A Relay
Protection and Logic Functions
Basic Protection
Figure 4.5 Negative-Sequence Time-Overcurrent Element 51QT
False negative-sequence current can transiently appear when a circuit breaker
is closed and balanced load current suddenly appears. To avoid tripping for
this transient condition, do not use a time-dial setting that results in curve
times below three cycles.
Table 4.11 Neutral Time-Overcurrent Settings (Sheet 1 of 2)
Setting Prompt Setting Range
Setting Name :=
Factory Defau lt
TOC TRIP LVL OFF, 0.50–16.00 A
a
0.10–3.20 A
b
0.13–2.00 mA
c
5.0–160.0 mA
d
51N1P := OFF
TOC CURVE SEL U1, U2, U3, U4, U5,
C1, C2, C3, C4, C5
51N1C := U3
TOC TIME DIAL 0.50–15.00
e
0.05–1.00
f
51N1TD := 1.50
EM RESET DELAY Y, N 51N1RS := N
CONST TIME ADDER 0.00–1.00 sec 51N1CT := 0.00
MIN RESPONSE TIM 0.00–1.00 51N1MR := 0.00
TOC TRQ CONTROL SELOGIC 51N1TC := 1
TOC TRIP LVL OFF, 0.50–16.00 A
a
0.10–3.20 A
b
0.13–2.00 mA
c
5.0–160.0 mA
d
51N2P := OFF
TOC CURVE SEL U1, U2, U3, U4, U5,
C1, C2, C3, C4, C5
51N2C := U3
TOC TIME DIAL 0.50–15.00
e
0.05–1.00
f
51N2TD := 1.50
EM RESET DELAY Y, N 51N2RS := N
CONST TIME ADDER 0.00–1.00 sec 51N2CT := 0.00
51QTC
SEL
OGIC
Torque Control
SELOGIC
Setting
(From Figure 4.1)
51QP
|3I
2
|
Setting
Torque Control Switch
51QT Negative-Sequence
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51QP Pickup
51QC Curve Type
51QTD Time Dial
51QRS Electromechanical
Reset? (Y/N)
51QCT Const. Time Add.
51QMR Min. Response
Pickup
Curve
Timeout
Reset
51QP
51QR
51QT
Torque Control
51QTC State Switch Position
Logical 1 Closed
Logical 0 Open
Logic Point TCQ Controls the Torque Control
Setting
51QRS = Reset Timing
Y Electromechanical
N 1 Cycle
Relay
Word
Bits