Southern Region Transmission System - I

1. Southern Region Transmission System - I CONTINGENCY MANAGEMENT-AN INTEGRATED APPORACH By Sri Kanikram AGM(O&M)

2. BREAKDOWNS • Breakdowns generally occur due to sudden failure of any of the transmission line components and may result in the following. • Loss of element availability • May even result in the unstable operation of grid. • Results in huge financial loss

3. BREAKDOWNS - TYPES • Based on the criticality of breakdowns they are broadly classified into two categories. • Minor/partial breakdowns These breakdowns may be due to any one of the component failures and can be restored in a day or two. • Major breakdowns • These may be due to tower collapse and may result in longer outage of that element. These are very critical and requires efforts for restoration on war footing basis.

4. BREAKDOWNS - CAUSES • Minor/Partial Breakdowns • Insulator decapping • Jumper opening • Conductor snapping • Earthwire snapping and falling on the conductor

5. BREAKDOWNS - CAUSES • Major Breakdowns • Tower Collapse

6. BREAKDOWNS - INDICATIONS • Tripping of line on E/F, P-P fault • Fail to reclose. • Further attempts to close result in immediate tripping. • Line will be declared under breakdown.

7. BREAKDOWNS – IMMEDIATE ACTIONS • Any type of breakdown whether it is minor or major, priority is for its early restoration. • Restoration of the element mainly involves the following important operations. • Identification of the fault at the earliest. • Mobilisation of resources • Effective planning for rectification of the problem.

8. BREAKDOWNS – FAULT LOCATION • Check the protection operations • Analyze the same with the help of Protection Engineer • Obtain the on line Fault locator reading of both the ends and correlate them. • Mobilize patrolling teams

9. BREAKDOWNS – FAULT LOCATION • Decide upon the section to be patrolled. • Organise the patrolling with two or three teams. • Ask them to be in continuous touch with the control room. • In the meanwhile find out the fault distance with the help of Off line fault locator. The past experience reveals that this has been a very handy tool with regard to accuracy in fault location. • Correlate the Off line fault locator reading with that of the On line fault locator reading. • If any deviations are observed revise the patrolling schedule to the distance as given by the Off line fault locator

10. BREAKDOWNS – FAULT LOCATION • Convey the revised patrolling schedule to the patrolling teams. • Based on the protection indications and previous history of component failures decide upon the probable cause of breakdown. • Mobilize Tools and plants for attending the problem.

11. MINOR BREAKDOWNS – T&P, MATERIAL AND MANPOWER MOBILISATION • Minor breakdowns normally of Conductor snapping, Decapping of insulator, E/W snapping etc., • Estimate the manpower requirement, tools and tackles required and accordingly mobilize the same from the local station or from the other stations. • Keep a list of T&P required for attending various minor breakdowns with the concerned TL office so that it helps as a ready reckoner during breakdowns. • Soon after getting the information about the location of fault rush the tools and plants to the respective location. • Communicate the fault location to the other patrolling teams and instruct them to reach the location where fault is existing.

12. LIST OF T&P - INSULATOR DECAPPING

13. LIST OF T&P – E/W SNAPPING • Experiences suggest that E/w occasionally falls on the conductor. Under such circumstances , it is not required to restring immediately and only clearing the earth wire from the conductor need to be done. • Discharge rod • Polypropylene rope • Single sheave pulley • Hack saw • Binding wire • Spanner set & tool box • E/W can be tied to the tower and can be restrung after availing the shut down.

14. LIST OF T&P – JUMPER OPENING • Jumper opening normally occurs due to breaking of jumper pad on the tension clamp. Under such circumstances jumper can be restored temporarily with the help of following material and tools • PG Clamps and T connectors • Conductor bit of 2m length • Discharge rods • Polypropylene rope • Belt ropes • Safety gadgets • Single sheave pulley • Spanner set along with tool box

15. BREAKDOWNS - IMAGES

16. MINOR BREAKDOWNS – STRATAGIES • Identify a responsible officer and assign him of the restoration work. • Arrange the other requirements such as vehicles, trucks, tractors and Diesel Generator set if required. • Identify different operations of the work clearly assign the individual responsibilities to different teams so that simultaneous completion of the different operations can be ensured. • Motivate the team of team work and set individual goals. • Never overlook safety.

17. MAJOR BREAKDOWNS – STRATAGIES • The first and fore most observation in case of major breakdowns is about the failure of PLCC communication. • In case of tower collapse normally tripping may occur due to operation of Ph-N or Ph-Ph-Ph fault. • Tripping on the above protection, failure to hold on further attempts and failure of PLCC communication is an indication of possible tower collapse.

18. MAJOR BREAKDOWNS – STRATAGIES • Obtain the on line fault locator reading and arrange for Off line fault locator testing. • Arrange for patrolling as already explained. • If the tower collapsed is noticed identify the numbers , types of tower No. of towers collapsed, their span length and report the same to Regional Disaster Management Group.

19. MAJOR BREAKDOWNS – STRATAGIES • The disaster Mnagement group at Regional level will take stock of the situation and a suitable decision to restore the line through permanent means or by providing ERS Bypass arrangement by considering various factors.

20. RESTORATION – VARIOUS FACTORS • Availability of spare towers. • Criticality of the element • Past data of maximum power flow. • Extent of damage and the no. of day required for permanent restoration. • No. of days required for ERS bypass.

21. MAJORBREAKDOWNS - RESTORATION • After making proper evaluation of the above factors the regional disaster Management group will take a appropriate decision as to restore the line through permanent means or by providing ERS bypass arrangement.

22. RESTORATION – ERS BYPASS • Instruct the custodian station of ERS material for making transport arrangement to the effected site. • Mobilise the ERS team and ask them to start survey at site for bypass arrangement. • Pool up all the resources, men, material and tools and plants.

23. RESTORATION – ERS BYPASS • Make activity wise schedule and prepare a bar chart. • Set a target for completion of each activity. • Assign responsibility of each activity to the individual team leaders. • Conduct every day team review meeting in the evenings and take appropriate corrective measures if required for achieving the targets.

24. RESTORATION - PERMANENT • Mobilize the disaster management team • Pool up the personnel and T&P to the site. • Check for foundation damage • Plan for debris removal. • Simultaneously plan for shifting of spare towers from the respective sites. • Identify site in charge and assign him of the total responsibility.

25. RESTORATION - PERMANENT • Make activity wise schedule and prepare a bar chart. • Set a target for completion of each activity. • Assign responsibility of each activity to the individual team leaders. • Conduct every day team review meeting in the evenings and take appropriate corrective measures if required for achieving the targets.

26. MAJOR BREAKDOWNS • Collapse of two towers in N’sagar – Raichur line in April’02 – Permanent restoration 5 days • Collapse of 8 towers in Talher – Kolar HVDC line in May’03 – ERS arrangement in 10 days • Collapse of 3 towers in N’sagar – Raichur line in the month of April’04 – Restored on ERS in 4days

27. COLLAPSE OF TOWERS-PERMANENT RESTORATION • N’sagar-Raichur line autoreclosed on 08.05.02 at 20.04hrs on B-N fault. • Subsequently tripped on 3phase to ground fault. • Upon patrolling on 09.05.02 collapse of towers observed at Loc. 522 and 523 of A type. • Breakdown situated approx. 200KM from N’sagar. • Situated in a remote area with nearest town at a distance of about 40KM from the site

28. COLLAPSE OF TOWERS- EXTENT OF DAMAGES • Loc 523 completely collapsed from waist level • Loc 522 collapsed from stub level • No damage to the foundations • Stub bend observed in 522 • Conductor and damage to other accessories

29. COLLAPSE OF TOWERS- RESTORATION ACTIVITIES • Mobilization of resources • De-tensioning of conductor and earth wire • Dismantling of tower debris • Observation to stub damages • Stub rectification • Tower erection • Stringing • Final checking & commissioning

30. COLLAPSE OF TOWERS- STUB RECTIFICATION • Remove the soil upto a depth of about 1.25mtrs and remove the concrete in all the four legs for visual examination of the stub. • Identify the maximum bent point on the stub and mark the same on all the stubs. • Cut all the stub portion 100mm below the marked point. • Measure the accurate length of the removed stub portion. • Prepare identical new stub portion of equal length to that of the removed portion. • Grind properly. • Carry out the strengthening process as given in the drawing.

31. COLLAPSE OF TOWERS- STUB RECTIFICATION

32. COLLAPSE OF TOWERS- OTHER ACTIVITIES • Allowed 24 hours concrete settlement time before starting tower erection • Completion of tower erection • Stringing • Commissioning

33. COLLAPSE OF TOWERS- FINAL DATE WISE ACTIVITY COMPLETION SCHEDULE

34. BREAKDOWNS – ERS BYPASS ARRANGEMENT IN TALCHER-KOLAR LINE

35. CONCLUSION • Timely, precise planning ,team work , regular review and follow up will have a greater bearing on the restoration time of the line whether it is through permanent means or through ERS

36. Thank you…