Sealing of persistent bushings oil leakage of 16/330kv,118MVA step up transformers at Jenna Power Station, in Niger State, Nigeria

PROJECT:

Repair (Sealing of oil Leakages) of 4 No bushings.

HISTORY:

History had is that the persistent oil leakage of 2x118MVA, 16/330KV power transformers at Jebba Hydro power Station dated back to over TWENTY YEARS without any meaningful solution. In the year 2009, I was engaged by Environmental Technologies limited who was given the contract to seal the oil leakage of the transformer which was the means of stepping up the generated power and evacuate such. I therefore led the team which was predominantly non technical personnel of Environmental Technology Limited. This made me to undertake a session of rudimentary training of the teams to achieve a level of technical assistance and safety at work. I must however state here that I enjoyed the assistance and contribution of some of them which enabled me to achieve the task with optimum efficiency.

EQUIPMENT:

  • 2 X 118 MVA, 16/330 KV Power Transformer at Jebba Hydro Power Station.
  • 2 No bushings on each of the transformers (2G2 AND 2G3) observed wet and leaking oilseriously.
2G2 CONDENSER BUSHINGS NAME-PLATE DATA:      2G3 CONDENSER BUSHINGS NAME-PLATE DATA: 
(Type)OS(Type)OS
(Form)L6(Form)L6
Rated Voltage362KvRated Voltage362Kv
Rated Current250ARated Current250A
Rated Frequency50HzRated Frequency50Hz
Rated Phase-to-Ground voltage209KvRated Phase-to-Ground voltage209Kv
Insulation Level1300KvInsulation Level1300Kv
Mass1170KgMass1170Kg
Serial No (Yellow Phase) Serial No (Yellow Phase) 
Serial No (Red Phase)772302 – 6Serial No (Red Phase)772302 – 7
Date of Manufacture1980Date of Manufacture1980
ManufacturerHitachi LtdManufacturerHitachi Ltd

 

JOB PLAN:

  • Feasibility study/physical inspection.
  • Complete draining of oil from transformer tank.
  • Initial Meggering of transformer
  • Opening and leaving manhole open to expel toxic gas.
  • Disconnection of bushing links and CT Terminals.
  • Dismantling of bushing and removal with crane.
  • Cutting of gasket/treatment of surfaces.
  • Replacement of gasket.
  • Reconnection of disconnected winding links and CT Terminals.
  • Cleaning of oil stains on transformer.
  • Megger-testing of transformer.
  • Holding vacuum on transformer.
  • Sending oil back into the transformer through held vacuum.
  • Commissioning tests/ Release of Equipment

PICTURES OF SITE WORK ON SEALING OF OIL LEAKAGES ON TRANSFORMER BUSHINGS.