Sel SEL-421 - Testing

R.3.35
Date Code 20111215 Reference Manual SEL-421 Relay
SELOGIC Control Equation Programming
Effective Programming
➤ Work in a top-down method, specifying and moving to more
detailed levels, until you have sufficient information to create
the settings. For simple tasks, one level may be sufficient. For
complex tasks, such as automated station restoration, you may
need several levels to move from idea to implementation.
Comments
SELOGIC control equation comments are very powerful tools for dividing,
documenting, and clarifying your programming. Even if you completely
understand your programming during installation and commissioning,
comments will be very helpful if you need to modify operation a year later.
Create these comments in the fixed and free-form SEL
OGIC control equations,
and store these comments in the SEL-421. Obtain comments to assist you in
using the ASCII interface or SEL configuration software, regardless of
whether you have the original files downloaded to the relay.
Comments add structure to free-form programming environments such as
Visual Basic, C, and free-form SEL
OGIC control equations. Example 3.23
shows how to use comments to divide and structure free-form SEL
OGIC
control equation programming.
EXAMPLE 3.23 Comments in
Free-Form SEL
OGIC Control Equation Programming
Use comments to divide and direct your eye through free-form
programming.
#
# This is a header comment that divides sections of free-form program-
ming
#
AMV003 := 15 * AMV003 # Explain this line here
#
# This comment is a header for the next section.
# Inputs: provide more detail for more complex tasks
# Outputs: describe how the programming affects the relay operation
# Processing: discuss how the programming itself operates
#
ASV004 := ACN01Q AND RB03 # First line of next section
Many texts on programming in various computer programming
languages suggest that you cannot include too many comments. The
main reason to include comments is that something you find obvious
may not be obvious to your coworker who will have to work with your
programming in the future. Adding comments also gives you the
opportunity to think about whether the program performs the
function you intended.
Testing
After documentation and comments, the next essential element of an effective
approach to programming is testing. Two types of testing are critical for
determining if programming for complex tasks operates properly. First, test
and observe whether the program performs the function you want under the
conditions 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
conditions that result from likely failure scenarios of the equipment in your