One possible scenario is steam drum level indicators on the boilers freeze, giving false signals to the control computers. This erroneous information then causes shutdowns as the control system/operators react to to the bad information.
I’ve seen this happen on systems with 6 different instruments measuring the same level in a drum.
I’ve worked may long hours keeping a power plants running during extrema cold weather taking what would be considered to be extraordinary measures. This was on plants that were supposed to be build to handle the cold.
It’s not unusual at all.
I want a root cause analysis.