Sel SEL-351S - Table 3.6 Negative-Sequence Time-Overcurrent Elements Settings; Figure 3.20 Negative-Sequence Time-Overcurrent Element 51 QT (with Directional Control Option)

3.26
SEL-351S Relay Instruction Manual Date Code 20080103
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Time-Overcurrent Elements
Accuracy
Negative-Sequence
Time-Overcurrent
Element
q From Figure 4.23.
Figure 3.20 Negative-Sequence Time-Overcurrent Element 51QT (with
Directional Control Option)
IMPORTANT: See Appendix F: Setting Negative-Sequence
Overcurrent Elements for information on setting negative-sequence
overcurrent elements.
To understand the operation of Figure 3.20, follow the explanation given for
Figure 3.14 in the preceding subsection Phase Time-Overcurrent Elements on
page 3.17, substituting negative-sequence current
3I
2
[3I
2
=I
A
+a
2
·I
B
+a·I
C
(ABC rotation), 3I
2
=I
A
+a
2
·I
C
+a·I
B
(ACB
rotation), where a = 1 ∠ 120° and a
2
=1∠−120°] for maximum phase
current I
P
and like settings and Relay Word bits.
Settings Ranges
Pickup: ±0.05 A secondary and ±3% of setting
(5 A
nominal phase current inputs, IA, IB, IC)
±0.01 A secondary and ±3% of setting
(1 A
nominal phase current inputs, IA, IB, IC)
Curve Timing: ±1.50 cycles and ±4% of curve time for currents between
(and including) 2 and 30 multiples of pickup.
51QP
3I
2
Setting
51QTC
Torque Control Switch
Directional Control
(asserted to logical 1
continuously if E32 = N)
q
(Level 1)
SEL
OGIC
Torque Control
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
51Q
51QR
51QT
Torque Control
TCQ State Switch Position
Logical 1 Closed
Logical 0 Open
Logic Point TCQ Controls the Torque Control Switch
Setting
51QRS = Reset Timing
Y Electromechanical
N 1 Cycle
TCQ
Relay
Word
Bits
SELOGIC
Setting
Table 3.6 Negative-Sequence Time-Overcurrent Elements Settings
(Sheet 1 of 2)
Setting Definition Range
51QP pickup 0.25–16.00 A secondary
(5 A nominal phase current inputs, IA, IB, IC)
0.05–3.20 A secondary
(1 A nominal phase current inputs, IA, IB, IC)
51QC curve type U1–U5 (US curves),
C1–C5 (IEC curves), recloser curves
(Ta bl e 9 .5 )—see Figure 9.1–Figure 9.20