1-4 B90 Low Impedance Bus Differential System GE Multilin1.2 UR OVERVIEW 1 GETTING STARTED1 c) UR SCAN OPERATIONThe UR-series devices operate in a cyclic scan fashion. The device reads the inputs into an input status table, solves thelogic program (FlexLogic™ equation), and then sets each output to the appropriate state in an output status table. Anyresulting task execution is priority interrupt-driven.Figure 1–3: UR-SERIES SCAN OPERATION1.2.3 UR SOFTWARE ARCHITECTUREThe firmware (software embedded in the relay) is designed in functional modules which can be installed in any relay asrequired. This is achieved with object-oriented design and programming (OOD/OOP) techniques.Object-oriented techniques involve the use of objects and classes. An object is defined as “a logical entity that containsboth data and code that manipulates that data”. A class is the generalized form of similar objects. By using this concept,one can create a protection class with the protection elements as objects of the class, such as time overcurrent, instanta-neous overcurrent, current differential, undervoltage, overvoltage, underfrequency, and distance. These objects representcompletely self-contained software modules. The same object-class concept can be used for metering, input/output control,hmi, communications, or any functional entity in the system.Employing OOD/OOP in the software architecture of the B90 achieves the same features as the hardware architecture:modularity, scalability, and flexibility. The application software for any UR-series device (for example, feeder protection,transformer protection, distance protection) is constructed by combining objects from the various functionality classes. Thisresults in a common look and feel across the entire family of UR-series platform-based applications.1.2.4 IMPORTANT UR CONCEPTSAs described above, the architecture of the UR-series relays differ from previous devices. To achieve a general understand-ing of this device, some sections of Chapter 5 are quite helpful. The most important functions of the relay are contained in“elements”. A description of the UR-series elements can be found in the Introduction to elements section in chapter 5.Examples of simple elements, and some of the organization of this manual, can be found in the Control elements section ofchapter 5. A description of how digital signals are used and routed within the relay is contained in the Introduction to Flex-Logic™ section in chapter 5.827823A1.CDRPKPDPOOPProtective ElementsProtection elementsserviced by sub-scanRead InputsSolve LogicSet Outputs
