Repair of transformers in Unit 1, Unit 2, Unit 3, and Unit 4 of CONTOURGLOBAL Maritsa East 3 TPP


Mednikarovo Village, Stara Zagora District

Assigned: 2018 / Completed: 2022

Project description

Project is part of the Repair Program of CONTOURGLOBAL Maritsa East 3 TPP. Assigned activities include repair of transformers, repair of 6 kV and 0.4 kV switchgears, electrical repairs of electrostatic precipitators (ESP) in Unit 1, Unit 2, Unit 3, and Unit 4.

Purpose of the Program is to restore reliability and design parameters (performance, efficiency, etc.) of the facilities and the power units.


  • Disconnection of transformers at LV and HV side;
  • Taking oil samples;
  • Revision of fans, oil-pumps, power supply switchboards; external cleaning; repair of leakages;
  • Filling up transformer oil, if necessary;
  • Control measuring of parameters: HV and LV windings insulation, idle running losses, tangent delta, ohmic resistivity, HV test of 6.3 kV and 15.75 kV busbar; earthing of transformer and surge arresters;
  • Connection of transformers;
  • Revision of current transformers connections on HV side;
  • Revision of airflow system – substitution of silica gel;
  • Revision of Yansen regulator;
  • Revision of fans and oil-pumps;
  • Revision of electrical switchboards;
  • Assistance during 72-hours test-run;
  • Test of current measuring transformers in 6.3 kV switchgears – current circuits insulation; ohmic resistivity of current transformers’ windings; Volt-Amper characteristics of current transformers;
  • Test of voltage measuring transformers in 6.3 kV switchgears – insulation, ohmic resistivity; transformation factor;
  • Test of relay protection.