Date Code 20010625
Setting SEL
OGIC
®
Control Equations
G-1
SEL-311L Instruction Manual
APPENDIX G: SETTING SEL
OGIC
®
CONTROL EQUATIONS
SEL
OGIC
®
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 SEL
OGIC
control equations.
Additional SEL
OGIC
control equation setting details are available in
Section 9: Setting the
Relay
(see also the Settings Sheets in the back of
Section 9
). See
SHO command (Show/View
Settings)
in
Section 10: Line Current Differential Communications and Serial Port
Communications and Commands
for a list of the factory settings included in a standard
shipment of a SEL
-
311L Relay.
R
ELAY
W
ORD
B
ITS
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.
Complete listings of Relay Word bits and their descriptions are referenced in Tables 9.3 and 9.4
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 3.47 in
Section 3: Line Current Differential, Distance, Out of Step, Overcurrent,
Voltage, Synchronism Check, and Frequency Elements
. Read the text that accompanies
Figure 3.47 (Table 3.8 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)
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