3.12
SEL-551 Relay Instruction Manual Date Code 20110408
Relay Elements and Logic
Time-Overcurrent Elements
Time-Overcurrent Elements
See the setting sheets in Section 4: Setting the Relay for time-overcurrent
element setting range information.
See Trip Logic on page 3.17 for examples of tripping with time-overcurrent
elements (setting TR) and unlatching tripping with time-overcurrent element
pickups (setting ULTR).
See Reclosing Relay on page 3.22 for an example of using time-overcurrent
element pickups to block reset timing (setting 79BRS).
Phase Time-
Overcurrent Elements
Two phase time-overcurrent elements (51P1T and 51P2T) are available (see
Figure 3.9). Their pickup settings (51P1P and 51P2P, respectively) are
compared to the magnitude of the maximum phase current (I
P
= maximum of
I
A
, I
B
, or I
C
).
Figure 3.9 Phase Time-Overcurrent Elements 51P1T and 51P2T
51P1P
(Max. Phase)
I
P
Setting
51P1TC
Torque Control Switch
51P1T Phase
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51P1P Pickup
51P1C Curve Type
51P1TD Time Dial
51P1RS Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51P1
51P1R
51P1T
Torque Control
51P1TC State Switch Position
Logical 1 Closed
Logical 0 Open
SEL
OGIC Setting 51P1TC Controls the Torque Control Switch
Setting
51P1RS = Reset Timing
Y Electromechanical
N 1 Cycle
Relay
Word
Bits
SELOGIC
Setting
51P2P
(Max. Phase)
I
P
Setting
51P2TC
Torque Control Switch
51P2T Phase
Time-Overcurrent Element
Curve Timing and Reset Timing
Settings
51P2P Pickup
51P2C Curve Type
51P2TD Time Dial
51P2RS Electromechanical
Reset? (Y/N)
Pickup
Curve
Timeout
Reset
51P2
51P2R
51P2T
Torque Control
51P2TC State Switch Position
Logical 1 Closed
Logical 0 Open
SEL
OGIC Setting 51P2TC Controls the Torque Control Switch
Setting
51P2RS = Reset Timing
Y Electromechanical
N 1 Cycle
Relay
Word
Bits
SELOGIC
Setting
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