Sel 551 - Figure 3.12 Negative-Sequence Time-Overcurrent Elements 51 Q1 T and 51 Q2 T

3.16
SEL-551 Relay Instruction Manual Date Code 20110408
Relay Elements and Logic
Time-Overcurrent Elements
Negative-Sequence
Time-Overcurrent
Elements
Two negative-sequence time-overcurrent elements (51Q1T and 51Q2T) are
available (see Figure 3.12). Their pickup settings (51Q1P and 51Q2P) are
compared to the magnitude of the negative-sequence current (3I
2
, derived
from I
A
, I
B
, and I
C
).
Figure 3.12 Negative-Sequence Time-Overcurrent Elements 51Q1T and
51Q2T
To understand the operation of Figure 3.12 for the negative-sequence time-
overcurrent elements (51Q1T and 51Q2T), follow the explanation given for
Figure 3.9 for the first phase time-overcurrent element (51P1T), substituting
3I
2
for I
P
and like settings and Relay Word bits.
IMPORTANT: See Appendix F for
information on setting negative-
sequence overcurrent elements.
51Q1P
31
2
Setting
51Q1TC
Torque Control Switch
51Q1T Negative-Sequence
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51Q1P Pickup
51Q1C Curve Type
51Q1TD Time Dial
51Q1RS Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51Q1
51Q1R
51Q1T
Torque Control
51Q1TC State Switch Position
Logical 1 Closed
Logical 0 Open
SEL
OGIC Setting 51Q1TC Controls the Torque Control Switch
Setting
51Q1RS = Reset Timing
Y Electromechanical
N 1 Cycle
Relay
Word
Bits
SELOGIC
Setting
51Q2P
31
2
Setting
51Q2TC
Torque Control Switch
51Q2T Negative-Sequence
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51Q2P Pickup
51Q2C Curve Type
51Q2TD Time Dial
51Q2RS Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51Q2
51Q2R
51Q2T
Torque Control
51Q2TC State Switch Position
Logical 1 Closed
Logical 0 Open
SEL
OGIC Setting 51P2TC Controls the Torque Control Switch
Setting
51Q2RS = Reset Timing
Y Electromechanical
N 1 Cycle
Relay
Word
Bits
SELOGIC
Setting