From rbc.ru:
[ColonelCassad] Equipment from Europe cannot be used to repair energy facilities in Ukraine due to differences in engineering solutions, writes the publication Ukraina began to experience an acute shortage of Soviet transformers with a voltage of 750 kV, each of which weighs up to 200 tons. This is reported by The Financial Times with reference to the head of the board of the national energy company "Ukrenergo" Volodymyr Kudrytsky.
The publication recalled that most of the Ukrainian energy system uses the old Soviet system. It operates at a higher voltage than the EU, which makes it incompatible with most Western equipment, which therefore cannot be used to replace damaged equipment.
Although some transformers were sent to Ukraine from former communist countries, such as Lithuania, most of the destroyed transformers must be rebuilt. “During the first eight months <...> we had a large supply of [spare] transformers. Now they are urgently needed, ”Kudritsky said. The head of Ukrenergo called a complete blackout theoretically possible.
In his opinion, Russia's attacks on Ukraine's energy infrastructure were planned not only by the military, but also by energy experts. Kudrytsky pointed out that Russian engineers knew Ukraine's power grid "like the back of their hand" because it was connected to the Russian system until last February.
Says Russian military journalist Boris Rozhin:
The case when communist transformers were suddenly needed under the conditions of the fascist regime and the persecution of communists.