Southern Region Transmission system -I

1. Southern Region Transmission system -I Introduction to Maintenance Philosophy , Preventive Maintenance & schedules By P C S Reddy Dy Mgr(OS) MCH Complex, R.P Road Secunderabad – 500 003 Tel: 040 -27717390,

2. POWERGRID OPERATIONAL OVERVIEW • Over 65000ckt KM of Transmission lines at various voltage levels of both HVAC and HVDC. • About 49000MVA of Transformation capacity. • Inter regional links thru HVDC back to back , FACTS, SVC etc., • Track record of achieving MOU Excellence in succession since 1993-94

3. TRANSMISSION LINES – BRIEF PRECEDENCE • Check for completion of construction activities • Shall be declared for commercial operation. • Major objective is to ensure reliable operation of the line with minimum outage. • Revenue realization of an entity depends on the continued operation of the line.

4. LINE AVAILABILITY - SIGNIFICANCE • CERC norms w.e.f 01.04.2004 stipulates, • Full transmission charges if availability is • ≥ 98% for HVAC system • ≥ 95% for HVDC system • Availability shall be calculated separately for both Inter-Regional and Intra-Regional elements of HVAC and HVDC. • MOU Target with GOI • Overall availability ≥99%

5. LINE AVAILABILITY -SIGNIFICANCE • If the availability is less than the targeted • Reduction in fixed charges component of transmission charges on pro-rata basis. • No transmission charges for Zero availability. • Incentive shall be given if the availability achieved is greater than the target. • Incentive • =(Availability achieved – Target availability)/100 *Equity

6. HVAC – OUTAGE EFFECT • In case of Outage of HVAC line loss of Incentive per hour of outage of one element – Rs7892/- • In case of outage of HVDC bipole line loss of incentive per hour outage of each pole is about Rs3,00,000/-

7. TRANSMISSION LINE AVAILABILITY – INFLUENCING FACTORS • Natural reasons such as floods, land slides, wind etc. • Sabotage attempts by the evil forces • Theft attempts by miscreants • Soil conditions • Defective material • Material aging

8. O&M OF TRANSMISSION LINES • Basic Philosophy • To enhance the life of the Tr. Line • To identify and carry out the rectification in the early stages to prevent the possible breakdowns. • To ensure maximum availability of the Transmission lines

9. TRANSMISSION LINE MAINTENANCE PHILOSOPHY • The effect of natural reasons i.e act of God which can not be controlled. We only should be prepared to meet any such eventualities. • The other effects such as thefts, sabotage, aging, material defects etc., can be controlled if they are properly addressed at appropriate time. • In order to address the effect of the above explained factors POWERGRID has formulated a maintenance philosophy in the year 1995 aiming to achieve the following objectives. • Objectives • To Ensure the maximum availability • To Enhance the life of the transmission line equipment.

10. TRANSMISSION LINE MAINTENANCE PHILOSOPHY • Philosophy • Maintenance philosophy is further categorized as under. • Preventive Maintenance • Periodic maintenance • Need Based maintenance • Annual maintenance • Breakdown maintenance.

11. MAINTENANCE METHODS • Periodic Maintenance • Regular inspection of the lines • Rectification of the defects which do not require shut down • Need based maintenance • Tower top patrolling • Thermo vision scanning • Puncture Insulator detection test

12. MAINTENANCE METHODS • Annual Maintenance • The defects of shut down nature, which are not critical, identified during routine inspection will be attended in a planned way once in a year by availing outage of the line. • Breakdown Maintenance • This maintenance will be taken up whenever the need arises on war footing basis.

13. POWERGRID NORMS – SALIENT FEATURES • Based on the maintenance philosophy POWERGRID formulated specific norms. • These norms will be in force till further revision • Patrolling frequency shall be based on the category of Terrain. • More emphasis for theft prone areas.

14. REVISED NORMS – TERRAIN CATEGORISATION • Normal Terrain • Which doesn’t require special consideration • Areas which are not prone for theft or insurgency. • Vulnerable Terrain • Forest, hills, hill slopes containing tall trees • Affected by pollution/flood/land slides • Theft prone • Power line(Above 132kV)/Railway/Highway/Major river X-ing • Areas prone to mining/blasting near transmission line

15. REVISED NORMS – TERRAIN CATAGORISATION • Most Vulnerable terrain • Critical land sliding • Insurgency/ terrorist prone area based on previous experience • Change of river course • Repeated theft

16. REVISED NORMS – PATROLLING CLASSIFICATION • Broadly classified as • Ground patrolling • Patrolling by walking along the line • Frequency is defined • Tower Top patrolling • Shall be carried out by climbing over the tower • Planned to find out the untraceable faults • In stretches having history of component failure • Regional OS will decide on the need basis

17. REVISED NORMS – GROUND PATROLLING FREQUENCY

18. REVISED NORMS – CONDITION MONITORING TECHNIQUES • Thermo vision scanning • Shall be carried out on need basis • Will be carried out for highly loaded(120% SIL) lines on sample basis (10% Every year) • Regional OS will decide further requirement based on the findings. • Punctured Insulator Detection • Shall be carried out for the lines having frequent insulator problems • Shall be planned as per the advise of the regional OS

19. REVISED NORMS – CONDITION MONITORING TECHNIQUES • Off line fault location/Signature analysis • Tool to find out permanent faults as well as for condition monitoring of the line. • Shall be carried out initially at the time of commissioning • Thereafter annually/during breakdowns depending on the criticality as decided by Regional OS.

20. REVISED NORMS - FORMATS • Maintenance schedules of transmission lines (Annexure –I) • Specifies frequency of patrolling and the target time for liquidation of both non shut down and shut down nature of defects • Check list for Ground Patrolling • List of items to be checked during patrolling

24. CHECK LIST FOR GROUND PATROLLING

26. REVISED NORMS - DOCUMENTATION • Monthly patrolling Program • The respective line-in-charge shall prepare a monthly program for the lines under his control as specified in Format-I • Reasons for non completion of the patrolling/maintenance targets programmed during the previous month along with rescheduled date to be mentioned. • Copy of the program to be sent to Regional OS along with the O&M monthly report

27. Monthly Patrolling Programme Office: Programme month: ___________________ Format-1 Signature of line In-charge

28. REVISED NORMS - DOCUMENTATION • Log Book of line defects (Format – II) • Helps in maintaining the patrolling frequency and adherence of maintenance schedule. • To be filled by the person carrying out the patrolling/maintenance. • Defects are to be entered under the respective heads. • Format has to be filled even when there are no defects.

29. LOG BOOK OF LINE DEFECTS Format- II

30. REVISED NORMS - DOCUMENTATION

31. REVISED NORMS - DOCUMENTATION

32. Summary of line defects (Prepared for attending the faults and to be retained in TL office) Format-III

33. Format -IV

36. Annexure to Monthly Maintenance Report Month Hub

37. TOWER CLIMBING PATROLLING REPORT (Non Outage) Format-V

38. TRANSMISSION LINES – PREVENTIVE MAINTENANCE • Based on the past experience the following are the frequently observed defects. • Rusting of stubs/legs • Damage to CP earthing • Damage to Coping • Missing Tower members • Missing DP/NP/PP • Missing Step bolts/ACD • Broken Insulators • Damaged Conductor • Displaced Vibration damper etc. • Infringing Right of way Ensure Safety Always by All Means

39. ROUTINE MAINTENANCE – RUSTING OF STUBS/LEGS CAUSES • Mainly due to the accumulation of soil around the leg. • Improper coping • Also depends on the type of the soil. Preventive action 1. Remove the soil 2. Clean the surface from the rusted portions using wire brush , etc 3. Allow it to dry 4. Apply priming coat 5. Apply two coats of black bitumen coal tar paint. 6. If required based on the site conditions, extend the chimney portion by a suitable height, in consultation with OS. Rusting initiated

40. MISSING TOWER MEMBERS Main diagnol bracing Diagnol member Redundant member

41. TRANSMISSION LINES – MISSING TOWER MEMBERS • The past experience reveals that • Perennial problem in some of the lines • Members removed are mostly in the bottom most panel. • Even in some places theft of members above the waist level was also reported. • Remedial Measures • Increased frequency of patrolling • Creation of awareness among the local public with the help of local revenue and police authorities.

42. PREVENTIVE MAINTENANCE – MISSING TOWER MEMBERS • Refixing of missing tower members • Has to be completed immediately soon after reporting the theft. • Maintain the stock of spare members. • Fabricate and refix • Ensure to fix the correct size members with suitable bolts & nuts and fasteners. • Punch the bolt

43. MISSING TOWER MEMBERS Refixing with under sized member

44. DEFECTS – SOME VISUALS Tower Leg Covered under soil CP Earthing Removed and bundled on the tower leg

45. CONCLUSION • The quality patrolling with Effective maintenance will not only enhance the life & security of the line but also reduces the outages. • Effective planning , leadership and guidance will definitely reduce the down time and maximize the availability. • By adopting the above explained maintenance philosophy and norms, we could achieve the MOU target availability of 98.5% in succession since 1993-94.

46. Thank You....