On my server, I built a small HV Solar Energy Plant at spawn, which outputs a maximum of 4,608 EU/T. It stores 90,000,000 EU at the plant, before outputting it to the industrial zones. I have the ability to turn-off the entire power grid at the plant, or turn off any individual industrial zone. I am also able to see who is consuming electricity at their factory when they are offline by using a light indicator.
To stop the power from flowing through a specific cable, I used an EU-Splitter Cable, and to activate my indicator lights, I used an EU-Detector Cable. Each are wired with redstone and connect to a switch.
In the future, I am planning to upgrade these features using ComputerCraft, thus being able to monitor and control everything from one central location.