GE Multilin B30 Bus Differential System 1-31 GETTING STARTED 1.2 UR OVERVIEW11.2UR OVERVIEW 1.2.1 INTRODUCTION TO THE URHistorically, substation protection, control, and metering functions were performed with electromechanical equipment. Thisequipment was gradually replaced by analog equipment, most of which emulated the single-function approach of their elec-tromechanical precursors. Both technologies required expensive cabling and auxiliary equipment to produce functioningsystems.Recently, digital electronic equipment has begun to provide protection, control, and metering functions. Initially, this equip-ment was either single function or had very limited multifunction capability, and it did not significantly reduce the cabling andauxiliary equipment required. However, recent digital relays are multifunctional, reducing cabling and auxiliaries signifi-cantly. These devices also transfer data to central control facilities and software using electronic communications. Thefunctions performed have become so broad that many users now prefer the term Intelligent Electronic Device (IED).It is obvious to station designers that the amount of cabling and auxiliary equipment installed can be even further reduced,to 20% to 70% of levels common in 1990, and achieve large cost reductions. This requires placing even more functionswithin the IEDs.Users of power equipment are also interested in reducing cost by improving power quality and personnel productivity, andin increasing system reliability and efficiency. These objectives are realized through software that is used to perform func-tions at both the station and supervisory levels. The use of these systems is growing rapidly.High-speed communication is required to meet the data transfer rates required by modern automatic control and monitoringsystems. Very high speed communications are required to perform protection signaling with a performance target responsetime for a command signal between two IEDs, from transmission to reception, of less than 3 milliseconds. This has beenestablished by the IEC 61850 standard.IEDs with such capabilities also provide significantly more power system data than was available, enhanced operations andmaintenance, and permit the use of adaptive system configuration for protection and control systems. This new generationof equipment is easily incorporated into automation systems, at both the station and enterprise levels. The GE Multilin Uni-versal Relay (UR) series meets these goals.1.2.2 HARDWARE ARCHITECTUREa) UR BASIC DESIGNThe UR is a digital-based device containing a central processing unit (CPU) that handles multiple types of input and outputsignals. The UR device can communicate over a local area network (LAN) with an operator interface, a programmingdevice, or another UR device.Figure 1–2: UR CONCEPT BLOCK DIAGRAMThe CPU module contains firmware that provides protection elements in the form of logic algorithms, as well as program-mable logic gates, timers, and latches for control features.
