Flexlogic Evaluation - GE D30 Instruction Manual

CHAPTER 5: SETTINGS
3. Assigning the output of an operator to a virtual output terminates the equation.
4. A timer operator (for example, "TIMER 1") or virtual output assignment (for example, " = Virt Op 1") can be used once
only. If this rule is broken, a syntax error is declared.

5.6.3 FlexLogic evaluation

Each equation is evaluated in the ascending order in which the parameters have been entered.
FlexLogic provides built-in latches that by definition have a memory action, remaining in the set state after the
set input has been asserted. These built-in latches are reset dominant, meaning that if logical "1" is applied to
both set and reset entries simultaneously, then the output of the latch is logical "0." However, they are volatile,
NOTE
meaning that they reset upon removal of control power.
When making changes to FlexLogic entries in the settings, all FlexLogic equations are re-compiled whenever
any new FlexLogic entry value is entered, and as a result of the re-compile all latches are reset automatically.
This section provides an example of logic implementation for a typical application. The sequence of steps is important to
minimize the work to develop the relay settings. Note that the example in the following figure demonstrates the procedure,
not to solve a specific application situation.
In the example, it is assumed that logic has already been programmed to produce virtual outputs 1 and 2, and is only a
part of the full set of equations used. When using FlexLogic, it is important to make a note of each virtual output used; a
virtual output designation (1 to 96) can be assigned only once.
1. Inspect the example logic diagram to determine if the required logic can be implemented with the FlexLogic
operators. If this is not possible, the logic must be altered until this condition is satisfied. Once done, count the inputs
to each gate to verify that the number of inputs does not exceed the FlexLogic limits, which is unlikely but possible. If
the number of inputs is too high, subdivide the inputs into multiple gates to produce an equivalent. For example, if 25
inputs to an AND gate are required, connect Inputs 1 through 16 to AND(16), 17 through 25 to AND(9), and the outputs
from these two gates to AND(2).
Inspect each operator between the initial operands and final virtual outputs to determine if the output from the
operator is used as an input to more than one following operator. If so, the operator output must be assigned as a
virtual output.
For the example shown, the output of the AND gate is used as an input to both OR#1 and Timer 1, and must therefore
be made a virtual output and assigned the next available number (that is, Virtual Output 3). The final output must also
be assigned to a virtual output as virtual output 4, which is programmed in the contact output section to operate relay
H1 (that is, contact output H1).
Therefore, the required logic can be implemented with two FlexLogic equations with outputs of virtual output 3 and
virtual output 4, shown as follows.
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 5-64: Logic example
FLEXLOGIC
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