G-2
Setting SEL
OGIC
®
Control Equations
Date Code 20001006
SEL-351 Instruction Manual
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)
Phase Time-Overcurrent Element 51PT Reset Indication
If phase time-overcurrent element 51PT is not fully reset, Relay Word bit 51PR is in the following
state:
51PR = 0
(logical 0)
If phase time-overcurrent element is fully reset, Relay Word bit 51PR is in the following state:
51PR = 1
(logical 1)
If phase time-overcurrent element 51PT is not fully reset, the element is either:
•
Timing on its curve
•
Already timed out
•
Is timing to reset (one-cycle reset or electromechanical emulation – see
setting 51PRS)
Relay Word Bit Application Examples – Phase Time-Overcurrent Element 51PT
Common uses for Relay Word bits 51P, 51PT, and 51PR:
51P
testing (e.g., assign to an output contact for pickup testing)
trip unlatch logic (see SEL
OGIC
Control Equation unlatch trip setting ULTR example
later in this section)
51PT
trip logic (see SEL
OGIC
Control Equation trip setting TR example later in this
section)
51PR
used in testing (e.g., assign to an output contact for reset indication)
Other Relay Word Bits
The preceding example was for a phase time-overcurrent element, demonstrating Relay Word bit
operation for pickup, time-out, and reset conditions. Other Relay Word bits (e.g., those for
definite-time overcurrent elements, voltage elements, frequency elements) behave similarly in their
assertion or deassertion to logical 1 or logical 0, respectively. The time-overcurrent elements (like
Summary of Contents for SEL-351
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