1. Construction and Condition Monitoring Lightning Arresters

3. LA Characteristics

6. LA

13. Basic circuit for LA testing

14. ZnO type Surge Arrester

15. Equivalent Circuit

18. Failure of 400kV LA

19. Failed LA hanging with Bus pipe

20. Shattered pieces of LA stacks

21. Close view of shattered pieces

22. Damaged Surge Monitor and shattered pieces of LA stacks

23. Another failed LA

24. FAILURE OF LAs

25. FAILURE OF LAs

26. Failure of LA

27. Failure of Surge Monitor after failure of LA

30. Third Harmonic Resistive Current - - 40-125 μ A 40-125 μ A LA (10-15Yrs.) - - 50-150 μ A 50-150 μ A LA >15Yrs. 20-50 μ A 10-40 μ A 10-20 μ A CGL 20-50 μ A 10-40 μ A 10-20 μ A Oblum 20-100 μ A 10-40 μ A 10-30 μ A Elpro 20-100 μ A 10-40 μ A 10-25 μ A Alstom LA (5-10Yrs.) LA (2-5Yrs.) LA (0-2Yrs.) Make

33. Capacitance and Tan Delta Measurement

34. Capacitance and Tan Delta Measurement on LA having 560 micro-Amp 1.12 270pF D 0.05 91pF C 0.065 89pF B 0.06 85pF A Remarks Tan Delta Capacitance Stack

35. Capacitance and Tan Delta Measurement on LA, 360kV having 595 micro-Amp 0.2 40pF D 0.2 40pF C 0.2 40pF B 1.0 80pF A Remarks Tan Delta Capacitance Stack

37. Failures of LAs in POWERGRID since 1999 0.5% 2 0 2 D 5 28 34 Total 0 16 19 LAs removed from service 5 12 15 LAs failed/ blasted 1.1% C 2.8% B 3.79% A % age failure Make

39. Displaced Gasket leading to moisture entry

40. Conduction marks on packing rubber

41. Cracked packing material

42. Rusted Spring

43. Conduction of ZnO discs

44. Corrosion on the Gasket Area