Schweitzer Engineering SEL-387-0, Instruction Manual

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4.8
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Control Logic
SEL
OGIC
Control Equation Sets (1—3) Variables
For setting group changes that do not make use of the SS n bits, namely those
using the GRO n serial port command or the
{GROUP}
front-panel pushbutton,
CHSG asserts about two cycles after the change command is received and
deasserts shortly after the group change is made. For these cases, CHSG does
not overlap the desired time period quite as precisely as when the SS
n bits are
used, but group changes initiated manually through the serial port or front
panel are inherently not as time critical, so a difference of a few cycles is not
likely to matter as much, if at all.
Active Setting Group
Retained for Power
Loss, Settings Change
The active setting group is retained if power to the relay is lost and then
restored. If a particular setting group is active (e.g., Setting Group 5) when
power is lost, it comes back with the same setting group active when power is
restored.
If settings are changed (for the active setting group or one of the other setting
groups), the active setting group is retained.
If settings are changed for a setting group other than the active setting group,
no interruption of the active setting group occurs (the relay is not momentarily
disabled).
If the settings change causes a change in one or more SEL
OGIC
control
equation settings SS1 through SS6, the active setting group can be changed,
subject to the newly enabled SS1 through SS6 settings.
SEL
OGIC
Control Equation Sets (1—3) Variables
Each setting group (1 through 6) has three sets of SEL
OGIC
control equation
variables for use in constructing SEL
OGIC
control equations. In the SEL-387
these variables are of two types:
➤
Timed variables
➤
Latch bits
The variables are processed in the order in which they appear in the Setting
Sheets. If variables that appear earlier are used as input to later variables, the
processing of both will occur within the same processing interval. If a later
variable is an input to an earlier variable, the scheme output will be delayed
one processing interval.
The SEL
OGIC
control equation sets must be enabled by Group settings
ESLS1, ESLS2, and/or ESLS3 in the configuration settings.
There are timed variables and latch bits available to the user. The three
SEL
OGIC
control equation sets have different mixes of variable types, as
shown below in Table 4.4 and Table 4.5 .
NOTE:
Make Active Setting Group
Switching Settings With Care.
The active setting group is stored in
nonvolatile memory so it can be
retained during power loss or settings
change. The nonvolatile memory is
rated for a finite number of "writes"
for all setting group changes.
Exceeding the limit can result in an
EEPROM self-test failure. An average
of 1 setting group change per day can
be made for a 25-year relay service
life.
This requires that SEL
OGIC
control
equation settings SS1 through SS6 be
set with some care. Settings SS1
through SS6 cannot result in
continuous cyclical changing of the
active setting group. Time setting TGR
qualifies settings SS1 through SS6
before changing the active setting
group.