13.36
SEL-400 Series Relays Instruction Manual Date Code 20171006
SELOGIC Control Equation Programming
SEL-311 and SEL-351 Series Users
Aliases
SEL-400 series relays provide the ability to alias relay word bit and analog quan-
tity names. To make SEL
OGIC programming more understandable, alias the
names of variables being used to something meaningful. For example, you could
assign PMV01 an alias of THETA and PMV02 an alias of TAN and then write a
SEL
OGIC equation of:
TAN := SIN(THETA)/COS(THETA)
See Alias Settings on page 12.20 for more information on creating aliases.
Testing
After documentation and comments, the next essential element of an effective
approach to programming is testing. Two types of testing are critical for deter-
mining if programming for complex tasks operates properly. First, test and
observe whether the program performs the function you want under the condi-
tions you anticipated. Second, look for opportunities to create conditions that are
abnormal and determine how your program reacts to unusual conditions.
For example, test your system in unanticipated, but possible conditions such as
loss of power, loss of critical field inputs, unexpected operator inputs, and condi-
tions that result from likely failure scenarios of the equipment in your system. It
is unlikely that you will find every possible weakness, but careful consideration
and testing for abnormal conditions will help you avoid a failure and may reveal
deficiencies in the normal operation of your system. Alternatively, you can sub-
stitute a remote bit or local bit that you can manually control to help exercise
your logic.
Modify your SEL
OGIC control equations to simulate the process. While you may
be unable to change the state of a discrete input easily, such as IN101, you can
substitute a logical 1 or logical 0 in your logic to simulate the operation of IN101
and observe the results. Alternatively, you can substitute a remote bit or local bit
that you can manually control to help exercise your logic.
Use the SER capabilities of the relay to monitor and record inputs, internal calcu-
lations, and outputs. For operations that occur very quickly, use the SER during
testing to reconstruct the operation of your logic.
Use the MET PMV and MET AMV commands to display the contents of the
protection or automation math variables.
SEL-311 and SEL-351 Series Users
You can convert logic that you have used in SEL-311 and SEL-351 series relays
to logic for an SEL-400 series relay. In the SEL-351 series relays, SEL
OGIC con-
trol equation programming is restricted to equations where the left side value,
LVALUE, is fixed. SEL-400 series relays use a combination of fixed and
freeform programming. Table 13.24 shows comparable features between the
fixed logic settings of the SEL-351-5, -6, -7 series relays and the corresponding
logic elements that can be programmed in an SEL-400 series relay using
freeform logic programming.
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