China's energy generation mix is not uniquely high in renewables! Where on earth did you get that idea from? China has about the same % renewable generation as Australia, about 1/3rd. Brazil has 80%, Norway 90%, some have near 100%.
What China does have is a very high carbon emission intensity of electricity generation thanks to over half capacity coming from coal.
How does the carbon intensity affect transformer operation or are you just adding non sequiteurs?