1. Static Relays contains electronic circuitry (Diodes, transistors, zener diodes, thyristors,logic gates …etc) ICs are widely being used in place of transistors as there are more reliable and compact comparator circuit compares V or I Comparator o/p applied to slave relay (Semi static) thyristor circuit (Fully static) Slave relay is EM relay which closes the contacts EM slave relay provides no. of o/p contacts at low cost Multi contact triggering arrangements are simple with EM relays

2. Classification of Static Relays Part of the circuitry which compares two actuating quantities is comparator Actuating Quantities – Magnitudes of V or I (or corresponding derived quantities) – Phase angle between V and I (or corresponding derived quantities) Amplitude Comparator compares the amplitude irrespective of angle between quantities Relay sends trip signal when operating quantity exceeds restraining quantity Phase comparator compares the phase angle irrespective of the magnitudes Relay sends trip signal when the phase angle between them < 90 0

3. Amplitude Comparators

4. Phase Comparators

5. Duality between comparators

6. Amplitude comparator used for phase comparison

9. Duality between comparators

10. Phase comparator used for amplitude comparison

13. Merits & Demerits of Static relays

15. Types of Amplitude & Phase Comparator Amplitude Comparators 1.Circulating Current type rectifier bridge comparators 2.Phase splitting type comparators 3.Sampling comparators Phase Comparators 1.Vector product phase comparator 2.Coincidence type phase comparators 1.Phase Splitting Type 2.Integrating Type 3.Rectifier bridge type 4.Time-bias type

16. Rectifier Bridge Type Amplitude Comparator

18. Phase Splitting Type Amplitude Comparator

19. Phase Splitting Type Phase Comparator

20. Integrating Type Phase Comparator

21. Rectifier Bridge Type Phase Comparator

22. Time bias type phase comparator

23. Static instantaneous over current relays

24. Static Definite time over current relay

25. Static Inverse time over current relay

26. Static Directional Over current relay

27. Why Numerical Relaying? To improve dependability as well as security Self checking facility Immune to variation in parameters of individual components Very low burden More flexibility because of programmable capability

28. Why Numerical Relaying? Contd.... Fibre optical communication with substation LAN Adaptive relaying schemes Permit Historical data storage Allow GPS (Geographical Positioning System) Time stamping

29. Why Numerical Relaying? Contd.... Numerical relays simplify interfacing with CTs and VTs Separate connection is not required, zero sequence voltages and currents can be derived inside the processor

30. Why Numerical Relaying? Contd.... Finally, Numerical relays represent best compromise between: economy and performance dependability and security complexity and simplicity speed and accuracy credible and conceivable

31. Analog Input Subsystem Simultaneous Sampling Scheme

32. Sample and Hold Circuit A S & H circuit which conceptually is a shunt capacitor with a switch holds the information (in terms of voltage)

33. Simultaneous Sampling Scheme: MUX Multiplexer is a collection of analog switches, which can be selected by supplying binary code Typically, power system applications involve more than one analog input To reduce the cost of the hardware, multiple channels are multiplexed through analog multiplexer to a single ADC Accuracy of the analog multiplexer depends on load impedance at the output terminal As S & H circuit has impedance in the range 10^8 to 10^12, no problem is encountered

35. Simultaneous Sampling Scheme All S & H amplifiers are set to hold state simultaneously This preserves the relative phase information between multiple analog signals Successive ADC which have a conversion time of 15-30 μ-sec An Anti-Aliasing filter is a low pass filter (LPF) used to cut-off the high frequency content in the input signal, connected after signal conditioning hardware

36. Schematic diagram of Typical Numerical Relay

37. Comparision between Electromechanical and Numerical Relays

39. Static Impedance Relay using Amplitude comparator

40. Static Reactance Relay

41. Static Mho Relay