5-182 F60 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUALFLEXLOGIC CHAPTER 5: SETTINGS55.6.4 FlexLogic exampleThis section provides an example of logic implementation for a typical application. The sequence of steps is important tominimize 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.Note that there is also a graphical interface with which to draw logic and populate FlexLogic equation entries. See theEngineer content at the end of the previous chapter.In the example, it is assumed that logic has already been programmed to produce virtual outputs 1 and 2, and is only apart of the full set of equations used. When using FlexLogic, it is important to make a note of each virtual output used; avirtual output designation (1 to 96) can be assigned only once.Figure 5-87: Logic example1. Inspect the example logic diagram to determine if the required logic can be implemented with the FlexLogicoperators. If this is not possible, the logic must be altered until this condition is satisfied. Once done, count the inputsto each gate to verify that the number of inputs does not exceed the FlexLogic limits, which is unlikely but possible. Ifthe number of inputs is too high, subdivide the inputs into multiple gates to produce an equivalent. For example, if 25inputs to an AND gate are required, connect Inputs 1 through 16 to AND(16), 17 through 25 to AND(9), and the outputsfrom these two gates to AND(2).Inspect each operator between the initial operands and final virtual outputs to determine if the output from theoperator is used as an input to more than one following operator. If so, the operator output must be assigned as avirtual 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 thereforebe made a virtual output and assigned the next available number (that is, Virtual Output 3). The final output must alsobe assigned to a virtual output as virtual output 4, which is programmed in the contact output section to operate relayH1 (that is, contact output H1).Therefore, the required logic can be implemented with two FlexLogic equations with outputs of virtual output 3 andvirtual output 4, shown as follows.FlexLogic provides built-in latches that by definition have a memory action, remaining in the set state after the setinput has been asserted. These built-in latches are reset dominant, meaning that if logical "1" is applied to both setand reset entries simultaneously, then the output of the latch is logical "0." However, they are volatile, meaning thatthey reset upon removal of control power.When making changes to FlexLogic entries in the settings, all FlexLogic equations are re-compiled whenever anynew FlexLogic entry value is entered, and as a result of the re-compile all latches are reset automatically.To implement FlexLogic using a graphical user interface, see the FlexLogic Design and Monitoring using Engineersection in the previous chapter.
