The manufacturers have been successful in producing numerical relays that are able to operate reliably in the harsh substation environment. Design & Principle NI 40/41 series relays are based on numerical microprocessor based technology. the selection and application of protective relays in the overall protection system, multifunctional numerical devices application for power distribution and industrial systems, and addresses some key concerns in selecting, coordinating, setting The numerical relay is defined as the relay which is constructed by using computer or microprocessor. Description and definition. It is also called numerical relay. It is generally made of following components 1. Sample and hold circuit 2. The digital protective relay is a protective relay that uses a microprocessor to analyze power system voltages, currents or other process quantities for the purpose of detection of faults in an electric power system or industrial process system. Hardware for Metering: In principle, the hardware setup discussed above can be used for both measurement and protection function. Anti-aliasing filter 3. Software: Numerical Relays are equipped with software to communicate with external device to program to Relay or one can program by navigating through the Relay Menu. The Numerical Aperture (NA) and f-number (f/#) of a lens measure the amount of light it can collect based on f, D, index of refraction (n), and Acceptance Angle (θ). Multiplexer 4. Numerical relays are based on the use of microprocessors. Electromechanical and static relays have fixed wiring and the setting is manual. Numerical relay is actually the digital relay as a unit for which manufacturers has developed standardized hardware, which can be used in conjunction with suitably developed software to meet variety of production requirements and applications. 1 Programmability of Numerical Relays: A Busbar Protection Relay Serves as a Traditional RTU Casper Labuschagne, Schweitzer Engineering Laboratories, Inc., Pullman, WA, USA Izak van der Merwe, Eskom Resources and Strategy Division, Cape Town, South Africa Abstract -- Numerical relays have revolutionized protection, control, metering, and communication in power systems. 36 COST OF NUMERICAL RELAYS Modern numerical protection devices have multiple protection elements and this technique makes the cost of the relay comparable with that of electromechanical and static relays … Transient testing is excellent method to validate the numerical relay algorithms based on the require application. ABB has delivered numerical relays worldwide. For example, we have the following protections in numerical relays in-built into one relay. A digital protective relay may also be called a "numeric protective relay". Figures 6a - 6e compare a variety of lens systems for a relay lens, or 1:1 imaging, application. A number of applications of numerical relays are discussed. NI 40/41 provides feeder protection applications with the best performance usability in its class and protection and numerical technology, backed by years of service performance across applications. A big difference between conventional electromechanical and static relays is how the relays are wired. The acceptance of numerical realsy as one-to-one substitutes for conventional relays seems to be fairly universal. Figure 4 illustrates the relationship between f/# and NA. APPLICATION OF NUMERICAL RELAYS FOR HV SHUNT REACTOR PROTECTION Z. Gajić, B. Hillstrőm, M. 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