H.3
Date Code 20060320 Instruction Manual SEL-311C Relay
Setting SELOGIC Control Equations
Relay Word Bits
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
➤ 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 Example of NOT Operator ! Applied to Multiple
Elements (Within Parentheses) on page H.5)
51PT trip logic (see Factory Settings Example (Using Setting TR) on
page 5.4)
51PR 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 the preceding phase time-overcurrent element
example) are unusual because they have a Relay Word bit (e.g., 51PR) 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.
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