The cornerstone of Tallinn's largest district's energy supply — replacement of the 63 MVA three-winding power transformer at Lasnamäe substation. The project's most critical requirement was zero downtime: the replacement had to be performed without interrupting the power supply to approximately 100,000 residents.
Lasnamäe is Tallinn's most populous district with approximately 100,000 residents, plus large shopping centers, industrial enterprises, and the Ülemiste City business center. The existing 63 MVA transformer had been in service for over 25 years and required replacement — insulation degradation had reached a critical phase.
Since interrupting Lasnamäe's power supply is excluded from an urban management perspective, we planned the entire replacement project on a dual-scheme principle: the new CG Power 63 MVA three-winding transformer (115/10.5/6.3 kV) was installed for paralleling before removing the old one. After load switching testing, we carried out a twenty-minute synchronous switching operation.
Additionally, all protection relay settings and AT supply circuits were updated. The project was completed exactly on schedule.
