Date Code 20020129
Control Logic
4-25
SEL-387E Instruction Manual
Limitations of SEL
OGIC
Control Equations
Any single SEL
OGIC
control equation setting is limited to 17 Relay Word bits that can be
combined together with the SEL
OGIC
control equation operators listed in Table 4.6. If this limit
must be exceeded, use a SEL
OGIC
control equation variable (SnVm) as an intermediate setting
step.
For example, assume that a trip equation (SEL
OGIC
control equation trip setting, TRn) needs
more than 17 Relay Word bits in its equation setting. Instead of placing all Relay Word bits into
TRn, program some of them into the SEL
OGIC
control equation setting, SnVm. Next use the
resultant SEL
OGIC
control equation variable output (Relay Word bit SnVm) in the SEL
OGIC
control equation trip setting, TRn.
The SEL
OGIC
control equation settings in the Group settings are limited to no more than 402
elements and 67 rising-edge or falling-edge operators. In the Global settings, they are limited to
no more than 81 elements and 14 rising-edge or falling-edge operators. Table 4.7 summarizes
this information.
An attempt to set the relay with more than 17 operands will result in the message "Maximum of
17 elements allowed in a SEL
OGIC
equation." The relay will then prompt the user to reenter the
equation. An attempt to save Group settings with more than 402 Relay Word bits or Global
settings with more than 81 Relay Word bits will result in the message "Overall SEL
OGIC
setting
size too large. Try simplifying equations." The relay will then return to the first nonhidden
SEL
OGIC
control equation for editing.
SEL
OGIC
control equation settings that are set directly to 1 (logical 1) or 0 (logical 0) also have
to be included in these limitations–each such setting counts as one element.
After SELogic control equation settings have been made and the settings are saved, the
SEL-387E Relay responds with the following message:
SCEUSE xx.x
GRnCHK yyyy
This message indicates that xx.x% of the maximum number of Relay Word bits are being used
(SCEUSE = SEL
OGIC
control equation use) and that the Global or Group n checksum (GBLCHK
or GRnCHK) is yyyy. The relay provides use and checksum results for the GLOBAL and
GROUP n settings.
Table 4.7: Maximums for SEL
OGIC
Control Equations
Group Setting Class
Global Setting Class
Relay Word bits per Equation
17
17
Relay Word bits per Setting Class
402
81
Equations per Setting Class (with two
16–output interface boards)
134
29
Rising- or Falling-Edge Operators per
Setting Class
67
14
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