4.22
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Control Logic
SEL
OGIC Control Equations
We could set 51P1TC to some combination of Relay Word bits. For
example, 51P1TC = IN105*!IN106. Here, we might want to supervise the
element as before, from an external directional relay, but only if there is no
input to IN106. IN106 could be a contact input from SCADA or a manual
control switch, to disable the operation of the Winding 1 inverse-time element.
So long as voltage is applied to IN106, the 51P1 element will not operate,
even if the directional relay gives permission.
We could set 51P1TC directly to 1. If 51P1TC = 1, the 51P1 element is
always ready to operate on current alone.
We could set 51P1TC directly to 0. If 51P1TC = 0, the 51P1 element will
never operate. This is one way, for example, to temporarily disable the 51P1
for some operational reason. It could be done using the SET command via a
serial port from a remote location.
Limitations of SELOGIC
Control Equations
Any single SELOGIC 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 4.7. 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 SELOGIC
control equation variable output (Relay Word bit SnVm) in the SEL
OGIC
control equation trip setting, TRn.
SEL
OGIC control equation settings in the Group Setting Class and Global
Setting Class can contain no more Relay Word bits, equations, or falling- and
rising-edge operators than the maximums shown in Tab le 4.8 .
An attempt to set the relay with more than 17 operands will cause the relay to
display the message
Maximum of 17 elements allowed in a SELOGIC
equation
and prompt you to reenter the equation. Exceeding the maximum
settings for each setting class will cause the relay to display the message
Overall SELOGIC setting size too large. Try simplifying equations.
The relay will then prompt you to edit the first unhidden SEL
OGIC control
equation.
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 SEL
OGIC control equation settings have been made and the settings are
saved, the SEL-387 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.
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