Electric devices (including infrastructural), are connected by networks, electricity can "travel" downstream just as easily as it can travel upstream unless specific mechanisms are engineered to avoid that, sometimes those mechanisms fail.
A power surge generated by oversupply in a power plant can affect burn both "downstream" devices that consume its electricity, as well as lateral unrelated networks, since they are all connected in a network.
I'm sure I'm wrong in a lot of points, but pretty confident in the fact that failures can flow upwards and cause blackouts downstream.
Electric devices (including infrastructural), are connected by networks, electricity can "travel" downstream just as easily as it can travel upstream unless specific mechanisms are engineered to avoid that, sometimes those mechanisms fail.
A power surge generated by oversupply in a power plant can affect burn both "downstream" devices that consume its electricity, as well as lateral unrelated networks, since they are all connected in a network.
I'm sure I'm wrong in a lot of points, but pretty confident in the fact that failures can flow upwards and cause blackouts downstream.