B
Control Equations & Relay Logic
SIMPRO-100
142 PRIM-2400C
B.4.1 Control Equation
Operators
Build control equation settings using logic similar
to Boolean algebra logic, by combining Relay
Word bits together using one or more of the six
control equation operators listed in Table B.3.
These operators are processed in a control
equation in the order shown in Table B.3.
Table B.3 Control Equation Operators
B.4.1.1 Control Equation AND
Operator [*]
Use the asterisk [*] symbol to denote logical AND
operations. When you use the [*] between two
Relay Word bits, both must pick up in order for
the relay to perform the operation in question. For
instance, if SV1 is the equation that controls
control equation variable 1, you could set SV1
equal to:
Equation B.1
With this setting, SV1 is true, or logical 1, when
both 50P1T and IN4 are true. Any number of
Relay Word bits may be ANDed together within
an equation, subject to the overall limitations
described in Section B.4.3, page 144.
B.4.1.2 Control Equation OR
Operator [+]
Use the plus [+] symbol to denote logical OR
operations. When you use the [+] between two
Relay Word bits, either can pick up to cause the
relay to perform the operation in question. For
instance, if SV1 is the equation controlling control
equation variable 1, you could set SV1 equal to:
Equation B.2
With this setting, SV1 is true, or logical 1, when
either 50P1T or 50P2T are picked up. Any
number of Relay Word bits may be ORed
together within an equation, subject to the overall
limitations described in Section B.4.3, page 144.
B.4.1.3 Control Equation Falling-Edge
Operator [\]
Use the falling-edge operator [\] with individual
Relay Word bits to cause a single
processing-cycle assertion when the Relay Word
bit changes state from logical 1 to logical 0. The
falling-edge operator [\] looks for Relay Word bit
deassertion (element going from logical 1 to
logical 0). The falling-edge operator [\] in front of
a Relay Word bit sees this logical 1 to logical 0
transition as a falling-edge and asserts to logical
1 for one processing interval. Do not apply the [\]
operator to groups of elements within
parentheses.
For example, suppose the control equation event
report generation setting is set with the detection
of the falling-edge of an underfrequency element:
Equation B.3
Operator Logic Function
/ Rising edge detect
\ Falling edge detect
( ) parentheses
!NOT
*AND
+OR
SV1 = 50PIT * IN4
SV1 = 50PIT + 50P2T
ER = ... + \81D1T
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