The power market operator is warning of worsening "multiple" threats to transmission lines in NSW and South Australia, with the line from NSW to Victoria at particular risk from bushfires in what is shaping up as a horror day for the energy market operator on Saturday.

As grid owners in NSW and Victoria struggle with swathes of their network still cut off after fires brought down key lines earlier this week, the Australian Energy Market Operator pointed to "the existence of abnormal conditions, namely severe and extreme bushfire conditions" threatening two states.