1.2 UR OVERVIEW
c) UR SCAN OPERATION
The UR device operates in a cyclic scan fashion. The UR reads the inputs into an input status table, solves the logic pro-
gram (FlexLogic™ equation), and then sets each output to the appropriate state in an output status table. Any resulting task
execution is priority interrupt-driven.
The firmware (software embedded in the relay) is designed in functional modules which can be installed in any relay as
required. 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 contains
both 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 repre-
sent completely self-contained software modules. The same object-class concept can be used for Metering, I/O Control,
HMI, Communications, or any functional entity in the system.
Employing OOD/OOP in the software architecture of the Universal Relay achieves the same features as the hardware
architecture: modularity, scalability, and flexibility. The application software for any Universal Relay (e.g. Feeder Protection,
Transformer Protection, Distance Protection) is constructed by combining objects from the various functionality classes.
This results in a 'common look and feel' across the entire family of UR platform-based applications.
As described above, the architecture of the UR relay is different from previous devices. In order to achieve a general under-
standing of this device, some sections of Chapter 5 are quite helpful. The most important functions of the relay are con-
tained in "Elements". A description of UR elements can be found in the INTRODUCTION TO ELEMENTS section. An
example of a simple element, and some of the organization of this manual, can be found in the DIGITAL ELEMENTS
MENU section. An explanation of the use of inputs from CTs and VTs is in the INTRODUCTION TO AC SOURCES section.
A description of how digital signals are used and routed within the relay is contained in the INTRODUCTION TO FLEX-
Figure 1–3: UR SCAN OPERATION
L90 Line Differential Relay
1 GETTING STARTED
serviced by sub-scan
1.2.3 UR SOFTWARE ARCHITECTURE
1.2.4 IMPORTANT UR CONCEPTS
GE Power Management