Southern Region Transmission System - I CONTINGENCY MANAGEMENT-AN INTEGRATED APPORACH By Sri Kanikram AGM(O&M)
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
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.
BREAKDOWNS - CAUSES • Minor/Partial Breakdowns • Insulator decapping • Jumper opening • Conductor snapping • Earthwire snapping and falling on the conductor
BREAKDOWNS - CAUSES • Major Breakdowns • Tower Collapse
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.
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.
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
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
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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
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
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.
COLLAPSE OF TOWERS- OTHER ACTIVITIES • Allowed 24 hours concrete settlement time before starting tower erection • Completion of tower erection • Stringing • Commissioning
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