H.2
SEL-311C Relay Instruction Manual Date Code 20060320
Setting SELOGIC Control Equations
Relay Word Bits
Relay Word Bits
Most of the protection and control element logic outputs shown in the various
figures in Section 3: Distance, Out-of-Step, Overcurrent, Voltage,
Synchronism Check, and Frequency Elements through Section 8: Breaker
Monitor and Metering Functions are Relay Word bits (labeled as such in the
figures). Each Relay Word bit has a label name and can be in either of the
following states:
➤ 1 (logical 1) or
➤ 0 (logical 0)
Logical 1 represents an element being picked up, timed out, or otherwise
asserted.
Logical 0 represents an element being dropped out or otherwise deasserted.
Complete listings of Relay Word bits and their descriptions are referenced in
Table 9.5 and Table 9.6.
Relay Word Bit
Operation Example–
Phase Time-
Overcurrent Element
51PT
As an example of protection element operation via the logic output of Relay
Word bits, a phase time-overcurrent element is examined. Refer to phase time-
overcurrent element 51PT in Figure 3.24. Read the text that accompanies
Figure 3.24 (Table 3.10 and following text). The following Relay Word bits
are the logic outputs of the phase time-overcurrent element:
51P indication that the maximum phase current magnitude is above the
level of the phase time-overcurrent pickup setting 51PP
51PT indication that the phase time-overcurrent element has timed out on
its curve
51PR indication that the phase time-overcurrent element is fully reset
Phase Time-Overcurrent Element 51PT Pickup Indication
If the maximum phase current is at or below the level of the phase time-
overcurrent pickup setting 51PP, Relay Word bit 51P is in the following state:
51P = 0 (logical 0)
If the maximum phase current is above the level of the phase time-overcurrent
pickup setting 51PP, Relay Word bit 51P is in the following state:
51P = 1 (logical 1)
If the maximum phase current is above the level of the phase time-overcurrent
pickup setting 51PP, phase time-overcurrent element 51PT is either timing on
its curve or is already timed out.
Phase Time-Overcurrent Element 51PT Time-Out Indication
If phase time-overcurrent element 51PT is not timed out on its curve, Relay
Word bit 51PT is in the following state:
51PT = 0 (logical 0)
If phase time-overcurrent element 51PT is timed out on its curve, Relay Word
bit 51PT is in the following state:
51PT = 1 (logical 1)
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