5-142 C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUALFLEXLOGIC CHAPTER 5: SETTINGS55.6 FlexLogic5.6.1 FlexLogic operandsFor flexibility, the arrangement of internal digital logic combines fixed and user-programmed parameters. Logic uponwhich individual features are designed is fixed, and all other logic, from contact input signals through elements orcombinations of elements to contact outputs, is variable. The user has complete control of all variable logic throughFlexLogic. In general, the system receives analog and digital inputs that it uses to produce analog and digital outputs. Thefigure shows major subsystems of a generic UR-series relay involved in this process.Figure 5-73: UR architecture overviewThe states of all digital signals used in the C70 are represented by flags (or FlexLogic operands, which are described later inthis section). A digital “1” is represented by a set flag. Any external contact change-of-state can be used to block anelement from operating, as an input to a control feature in a FlexLogic equation, or to operate a contact output. The stateof the contact input can be displayed locally or viewed remotely via the communications facilities provided. If a simplescheme where a contact input is used to block an element is wanted, this selection is made when programming theelement. This capability also applies to the other features that set flags: elements, virtual inputs, remote inputs, schemes,and human operators.If more complex logic than shown in the figure is required, it is implemented via FlexLogic. For example, to have the closedstate of contact input H7a and the operated state of the phase undervoltage element block the operation of the phasetime overcurrent element, the two control input states are programmed in a FlexLogic equation. This equation ANDs thetwo control inputs to produce a virtual output that is then selected when programming the phase time overcurrent to beused as a blocking input. Virtual outputs can only be created by FlexLogic equations.
