The original BBC report is here;
Climate change: Electrical industry's 'dirty secret' boosts warming
https://www.bbc.co.uk/news/science-environment-49567197
Sulphur hexafluoride, or SF6, is a a hugely effective insulating material for medium and high-voltage electrical installations, and has the highest global warming potential of any known substance. It is 23,500 times more warming than carbon dioxide (CO2).
It leaks into the atmosphere. Emissions have been growing, apparently due to the increasing number of wind power projects. I suppose it's an unintended consequence.