This course will be helpful for diploma and undergraduate students as well as industrial professionals. Course is a combination of theory as well as practical knowledge used on site. This course will discuss about Numerical Protection Relay used in Power System Protection. It will give introduction or basics of numerical relay and explains drawbacks of Electromechanical and Static relay. Numerical protection relay Sub-systems like Analog input subsystem, Analog interface, Data acquisition system, Digital output and input system are discussed. Function of various blocks e.g. Analog Input Isolation, I/V Converter, Low Pass (Anti-Aliasing) Filter, S/H Circuit, Analog Multiplexer, A/D Converter are also explained. Overall typical Architecture of microprocessor or digital or numerical relay is discussed. This course also explain the hardware implementation for Differential, Directional and Distance protection. Because of communication facility these relays are used in SCADA system and substation can be called as unmanned Substation. Regional Load Dispatch Centres (LDC) can control the power flow. Technical specification and functions or facilities of 7SJ66 Siemens O/c and E/f relay are also explain. SIPROTEC 7SJ66 is a numerical protection, control and monitoring device. SIPROTEC 7SJ66 is features flexible protection functions. Up to 20 protection functions can be added according to individual requirements. You are also requested to visit my You Tube Chanel.