
U.3.13
Date Code 20020501
User’s Guide
SEL-421/SEL-421-1 Relay
PC Software
Expression Builder
Expression Builder
SEL
OGIC
control equations are a powerful means for customizing relay
performance. Creating these equations can be difficult, because of the large
number of relay elements (Relay Word bits) and analog quantities in the relay.
The
AC
SEL
ERATOR
software simplifies this process with the Expression
Builder, a rules-based editor for programming SEL
OGIC
control equations.
The Expression Builder organizes relay elements, analog quantities, and
SEL
OGIC
control equation variables and focuses your equation decision-
making. The Expression Builder checks basic rules and flags mistakes in
SEL
OGIC
control equation settings.
Access the
Expression Builder
Settings dialog boxes in the Relay Editor window show an “EB” option button
(see
). Click the EB option button to use the Expression Builder.
Figure 3.17
Location of EB Option Button.
Expression
Builder Organization
The Expression Builder dialog box is organized into two main parts
representing the left side (LVALUE) and right side (RVALUE) of the
SEL
OGIC
control equation. (The LVALUE is fixed for all settings except
Protection Free-Form SEL
OGIC
and Automation Free Form SEL
OGIC
settings;
see
Control Equations on page R.3.5 in the Reference
shows the two sides of the Expression Builder, with the
SEL
OGIC
control equation that you are constructing at the top of the dialog
box. Note the dark vertical line and the equals sign (:=) separating the
equation left and right sides.
Figure 3.18
The
AC
SEL
ERATOR
Expression Builder.
Содержание SEL-421
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