OVERCURRENT PROTECTION

1 OVERCURRENT PROTECTION . ( )/EEE Dept. of EEE SRM University Page 1. time -CURRENT CHARACTERISTICS. Definite- time OVERCURRENT Relay Instantaneous OVERCURRENT Relay Inverse- time OVERCURRENT Relay Inverse Definite- time OVERCURRENT Relay Very Inverse- time OVERCURRENT Relay Extremely Inverse- time OVERCURRENT Relay Special characteristics Method of Defining shape of time -current Characteristics Technique to Realise Various time -current Characteristics using Electromechanical Relays 2. ( )/EEE Dept. of EEE SRM University Page 2. Definite- time and Inverse- time characteristic of OVERCURRENT relays 3. ( )/EEE Dept. of EEE SRM University Page 3. Very Inverse- time OVERCURRENT Relay 4. ( )/EEE Dept. of EEE SRM University Page 4. Extremely Inverse- time OVERCURRENT Relay 5 , very inverse- time and extremely inverse- time characteristics ( )/EEE Dept. of EEE SRM University Page 5. Method of defining shape of time -current characteristics The general expression for time -current characteristics is given by 6.

2 ( )/EEE Dept. of EEE SRM University Page 6. Current settings Standard ccharacteristic 7. ( )/EEE Dept. of EEE SRM University Page 7. 8. ( )/EEE Dept. of EEE SRM University Page 8. 9. ( )/EEE Dept. of EEE SRM University Page 9. 10. ( )/EEE Dept. of EEE SRM University Page 10. 11. ( )/EEE Dept. of EEE SRM University Page 11. 12. ( )/EEE Dept. of EEE SRM University Page 12. Over current PROTECTION schemes time -graded system 13. ( )/EEE Dept. of EEE SRM University Page 13. Current-graded system 14. ( )/EEE Dept. of EEE SRM University Page 14. A combination of time and current grading 15. ( )/EEE Dept. of EEE SRM University Page 15. 16. ( )/EEE Dept. of EEE SRM University Page 16. 17. ( )/EEE Dept. of EEE SRM University Page 17. 18. ( )/EEE Dept. of EEE SRM University Page 18. 19. ( )/EEE Dept. of EEE SRM University Page 19. 20. ( )/EEE Dept. of EEE SRM University Page 20. 21. ( )/EEE Dept. of EEE SRM University Page 21. 22. ( )/EEE Dept. of EEE SRM University Page 22.

3 23. ( )/EEE Dept. of EEE SRM University Page 23. Reverse power or Directional Relay 24 Induction disc type directional relay ( )/EEE Dept. of EEE SRM University Page 24. 25. ( )/EEE Dept. of EEE SRM University Page 25. 26 Induction cup type directional relay ( )/EEE Dept. of EEE SRM University Page 26. 27. ( )/EEE Dept. of EEE SRM University Page 27. Directional relay connections 28. ( )/EEE Dept. of EEE SRM University Page 28. Directional over current relay 29. ( )/EEE Dept. of EEE SRM University Page 29. PROTECTION of parallel feeders 30. ( )/EEE Dept. of EEE SRM University Page 30. PROTECTION of ring mains 31. ( )/EEE Dept. of EEE SRM University Page 31. 32. ( )/EEE Dept. of EEE SRM University Page 32. EARTH FAULT AND PHASE FAULT PROTECTION . Earth fault relay and over current relay Earth fault Protective schemes 33. ( )/EEE Dept. of EEE SRM University Page 33. 34. ( )/EEE Dept. of EEE SRM University Page 34. Combined Earth Fault and Phase fault protective scheme Two over current and one earth fault relay 35.

4 ( )/EEE Dept. of EEE SRM University Page 35. 36 Two over current and one earth fault relay ( )/EEE Dept. of EEE SRM University Page 36. Directional earth fault relay 37. ( )/EEE Dept. of EEE SRM University Page 37. 38. Five limb VT. ( )/EEE Dept. of EEE SRM University Page 38. Static over current relay 39. ( )/EEE Dept. of EEE SRM University Page 39. Instantaneous over current relay 40. ( )/EEE Dept. of EEE SRM University Page 40. Definite time over current relay 41 Block diagram of Definite time over current relay ( )/EEE Dept. of EEE SRM University Page 41. 42. ( )/EEE Dept. of EEE SRM University Page 42. Inverse- time over current relay 43 Block diagram of Inverse- time over current relay ( )/EEE Dept. of EEE SRM University Page 43. Directional over current relay 44 Block diagram of Directional over current relay ( )/EEE Dept. of EEE SRM University Page 44. Numerical over current relay Microprocessor-based over current relay Microcontroller-based over current relay Digital Signal Processor (DSP)-based relays Field Programming Gate Arrays (FPGA)-based over current relays.

5 Artificial Neural Network (ANN) based numerical relays 45. ( )/EEE Dept. of EEE SRM University Page 45. REVIEW QUESTIONS. 46. ( )/EEE Dept. of EEE SRM University Page 46. 47. ( )/EEE Dept. of EEE SRM University Page 47.