GE Multilin N60 Network Stability and Synchrophasor Measurement System 5-895 SETTINGS 5.4 FLEXLOGIC™55.4FLEXLOGIC™ 5.4.1 INTRODUCTION TO FLEXLOGIC™To provide maximum flexibility to the user, the arrangement of internal digital logic combines fixed and user-programmedparameters. Logic upon which individual features are designed is fixed, and all other logic, from digital input signals throughelements or combinations of elements to digital outputs, is variable. The user has complete control of all variable logicthrough FlexLogic™. In general, the system receives analog and digital inputs which it uses to produce analog and digitaloutputs. The major sub-systems of a generic UR-series relay involved in this process are shown below.Figure 5–32: UR ARCHITECTURE OVERVIEWThe states of all digital signals used in the N60 are represented by flags (or FlexLogic™ operands, which are describedlater in this 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 desired, this selection is made when programming the ele-ment. This capability also applies to the other features that set flags: elements, virtual inputs, remote inputs, schemes, andhuman operators.If more complex logic than presented above is required, it is implemented via FlexLogic™. For example, if it is desired tohave the closed state of contact input H7a and the operated state of the phase undervoltage element block the operation ofthe phase time overcurrent element, the two control input states are programmed in a FlexLogic™ equation. This equationANDs the two control inputs to produce a virtual output which is then selected when programming the phase time overcur-rent to be used as a blocking input. Virtual outputs can only be created by FlexLogic™ equations.Traditionally, protective relay logic has been relatively limited. Any unusual applications involving interlocks, blocking, orsupervisory functions had to be hard-wired using contact inputs and outputs. FlexLogic™ minimizes the requirement forauxiliary components and wiring while making more complex schemes possible.
