Schweitzer Engineering Laboratories SEL-351 - Appendix G: Setting Sel Ogic Control Equations; Relay Word Bits; Phase Time-Overcurrent Element 51 PT Pickup Indication; Relay Word Bit Operation Example - Phase Time-Overcurrent Element 51 PT

Date Code 20001006 Setting SELOGIC
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Control Equations G-1
SEL-351 Instruction Manual
APPENDIX G: SETTING SELOGIC
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CONTROL EQUATIONS
SELOGIC
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Control Equations combine relay protection and control elements with logic operators
to create custom protection and control schemes. This appendix shows how to set the protection
and control elements (Relay Word bits) in the SELOGIC Control Equations.
Additional SELOGIC Control Equation setting details are available in Section 9: Setting the Relay
(see also Settings Sheets 12 through 16 in the back of Section 9). See the SHO command
(Show/View Settings) in Section 10: Serial Port Communications and Commands for a list of
the factory settings the SEL-351 Relay ships with in a standard relay shipment.
RELAY WORD BITS
Most of the protection and control element logic outputs shown in the various figures in Section 3
through Section 8 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.
A complete listing of Relay Word bits and their descriptions are referenced in Table 9.3 in
Section 9: Setting the Relay.
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 3.14 in Section 3: Overcurrent, Voltage, Synchronism Check, Frequency, and Power
Elements. Read the text that accompanies Figure 3.14 (Table 3.3 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)
Courtesy of NationalSwitchgear.com