Originally Posted by
Flaflyer
There is the problem. Even with two power sources, there is one transfer switch, and if it fails, power is cut.
Many sophisticated electrical systems do not rely on "transfer switches". An electrical "bus" may have two, three or more supply breakers. If the system senses zero voltage on the bus, it then locks out the first breaker, and closes the second breaker. If the second breaker fails to restore power, then the system locks out the first two breakers and closes the third.
A human person may also take control of the system and manually close breakers.