(3)
Chinese businesses and multi-national companies manufacturing
transformers in China, which are later plugged into the electric grid
in the United States.

Chinese power equipment can be embedded with software and hardware
that can be remotely accessed, enhancing China’s ability to commit
cyberattacks. Because power transformers are huge and weigh between
100 and 400 tons, it is not easy to identify embedded software or
hardware. There is also a potential hardware risk since counterfeit
items can be easily put into large power transformers.”

You can read Trump’s EO here:

https://www.federalregister.gov/documents/2020/05/04/2020-09695/securing-the-united-states-bulk-power-system

What prompted Trump’s EO was this prior report right here. The
Department of Energy found in this report, that there were :

6 - US power transformer manufacturers

30- Chinese power transformer manufacturers.

You can read the report here:
https://www.energy.gov/sites/prod/files/20