SEL
OGIC
Control Equations
4-3
SEL-300G Instruction Manual
Date
Code
20060731
If neutral time-overcurrent element 51NT is
timed out
on its curve, Relay Word bit 51NT is in
the following state:
51NT = 1 (logical 1)
Neutral Time-Overcurrent Element 51NT Reset Indication
If neutral time-overcurrent element 51NT is
not fully reset
, Relay Word bit 51NR is in the
following state:
51NR = 0 (logical 0)
If neutral time-overcurrent element is
fully reset
, Relay Word bit 51NR is in the following state:
51NR = 1 (logical 1)
If neutral time-overcurrent element 51NT is
not fully reset
, the element is either:
•
timing on its curve
•
already timed out
•
timing to reset (one-cycle reset or electromechanical emulation—see setting 51NRS)
Relay Word Bit Application Examples—Neutral Time-Overcurrent Element 51NT
Common uses for Relay Word bits 51N, 51NT, and 51NR:
51N
testing (e.g., assign to an output contact for pickup testing)
trip unlatch logic
51NT trip
logic
51NR
used in testing (e.g., assign to an output contact for reset
indication)
Other Relay Word Bits
The preceding example was for a neutral 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 the preceding neutral time-overcurrent element example) are unique because they
have a Relay Word bit (e.g., 51NR) that asserts for the reset state of the element.
Relay Word bits are used in SEL
OGIC
control equations, which are explained in the following
subsection.
Summary of Contents for SEL-300G
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