Siemens will produce four 40kV transformers for UK network operator National Grid for the 73km-high-voltage direct-current cross-channel link.
The German firm said the new transformers "are quieter, have lower transmission losses and will significantly improve the system's reliability".
The transformers will be made in Siemens' Nuremberg factory, and completion of the upgrade is expected to be in mid-2019, the firm added.
An interconnector between the UK and France has existed since 1961 when a 160MW system was installed.
By 1986, this had been replaced by the 2GW HVDC link.
Three further links with France have been proposed. The 1GW ElecLink — which will see a 69km cable installed in the Channel Tunnel to carry power between the two countries — was approved in early 2017. There are also plans for the 1.4GW FAB and 1GW IFA2 links.