How to knock down electronics on a large scale?

Question

They say all is fair in love and war. When we plan to invade our enemy's planet, we don't want fair. We want to strike them while they're down. We infiltrated sleeper agents in key points of their infrastructure. Those agents have laid down the ground work we need when the day comes.

Agent 2215 is a worker at Treenadia City West Fusion Power Facility. The plant powers half of the capital city, including its most critical infrastructures: the Planetary Defence Army's military base in TC, the Interplanetary Communication Hub and the sector headquarters for the Federal Fleet. 2215 can get us unlimited access to the plant's control systems.

But we can't just switch power off, they will be back up and running before we can even strike. We need something more disruptive. Our initial thought was to turn their own infrastructure against them. Turn the fusion plant into an EMP generator, and let it propagate through the grid. The question is: how?

The plant uses tokamak-style reactors. Maybe we could use their magnetic confinement in some way. The plant also has large underground energy storage facilities. Maybe we could overload them to trigger an explosive reaction. Maybe there are other options we overlooked.

We need to disable electronics in a 500km radius at minimum, but we'd like to extend our strike up to a 2500km radius as much as possible. More than that, we need to disable orbital defenses, all in one fell swoop. How they are disabled doesn't really matter, we only need a good 6-12 hours window of opportunity for our invasion.

The Interplanetary Communication Hub has large, powerful antennae. We're thinking those may help propagate an EM wave much further than it normally would, but we're not quite sure if and how it will work.

Help us put the finishing touch on our plan, and we shall show them the might of the Alliance.

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To clarify on operational objectives, we need a way to:

• Prevent interplanetary communication by disabling the Comm Hub.
• Disable static surface defense (anti-air canons, radar arrays).
• Disable mobile surface defense (ground vehicles, naval ships, aircrafts).
• Disable orbital defense (orbital station, satellites, spaceships) as much as possible.

At minimum, we need to disable defense sensors and/or targeting systems. A cannon that cannot find its target is as good as destroyed in our case.

Answer 1

You are attacking the wrong place. Power plants are well defended and easily repairable. And the effect of losing a power plant is rather easily mitigated. What you want to go after is the power distribution grid. 

The power distribution grid is pretty much like highways for electric power. Cause a disruption on a highway, and you know what happens: instant congestion, confusion and desperate attempts to re-route around the problem. When it comes to electric power, these things happen in seconds, and unless your grid is resilient against disruption, you can trigger a major power-out this way. 

The 2006 European Blackout and the 2003 North American ditto were both caused by the power grid failing. The European case is particularly interesting in that it shows how a relatively small disruption can cascade over large areas. When one critical line was closed down, the power rerouted to neighbouring lines. However, due to them already being being operated close to the safety margin, the extra load tripped the overload safeties and took those lines off the grid as well. This meant that even more power needed to be rerouted to other lines, which tripped them in return. And so the domino effect spread all over the continent and split it in three. 

The amusing part here is that for you as an attacker, you may also want to attack major consumers of power rather than only producers, because a sudden surplus of power can be a much bigger problem than a power deficit. Power distribution is usually quite good at handling deficits by doing load-shedding, that is to start disconnecting lower priority consumers in order to keep the high priority consumers — like the military — online. But what do you do when you suddenly have many gigawatts of extra power and nowhere to put it?! If you suddenly get 300 Volts at 100 Hz in your wall socket when you expect only 120 V at 60 Hz, things will start breaking and burning up. This cannot be allowed to happen, so they will start shutting down the grid completely rather than let this happen. 

In summary: what you want is to upset the delicate balance in the entire power system. Disrupt key distribution lines and distribution centers; force big power sinks off the grid in a surprising and uncontrollable manner; wreak havoc for those that try to balance the power grid.

Then as they scramble to try to understand why everything is going haywire, you launch your attack...

EDIT:

After your edits... look, what are you really after? Are you looking for a realistic way to do that big laundry list of items you added? Or are you looking for a way of making your Agent 2215 become a key person in your story by somehow opening the door for the attack?

If it is the first case then I would accuse your military commanders of gross negligence if the only thing they do in preparation for invading a planet is to send in just one agent and hope that this one person can pull off that huge feat. This simply is not credible for a story.

If it is the second case then you probably need to drop the idea of making the agent cause something go "phwoom" and from that hope that the big list of items drop offline.

What you can do however to make the agent be a key person is - for instance - to be employed somewhere within the power distribution system (working in a power plant would fit that) and have the agent send off a list of targets in the power grid that will cause the maximum amount of havoc on their defences, sensor grids, vital infrastructure and similar things.

Another way can be for the agent to be like Six in the new Battlestar Galactica when she opens the door for the Cylon attack. She does not do any damage herself but she does disable the defences, not by using brute force, but by providing data access to critical systems and allowing the Cylons to simply tell them to shut down.

So please be clear about what you actually want - credibility or drama centered on your agent - because the answers will change greatly depending on this.

Answer 2

The agent on the ground is a distraction, and keeps the enemy from looking at where the real action is taking place.

Your space fleet has managed to place a powerful magnetic generator in orbit around the Sun, and is now inducing the conditions to create a powerful solar flare. This flare will be timed so the energetic output and plasma will impact the enemy planet, inducing a world wide EMP pulse into the power and communications grid, much like the Carrington Event of 1859.

As an added bonus, this will also negatively affect orbital infrastructure and potentially any enemy spacecraft in orbit around the planet. Enemy space stations, battleships, Laserstars and other weaponry and sensor systems will be blinded and out of action for a period of time, depending on how hardened they are and how long it takes to reboot computers and do necessary repairs.

Assuming your space fleet was parked outside of the "cone" of charged particles released by the flare, and can move quickly into attack position and orbit around the planet, you will be in the High Guard position inside their Hill Sphere before they can take steps to repel your forces, and be ready to dictate terms.

Answer 3

Have your agent give you access to the computers of the plant. The plant might be connected to the rest of the infrastructure, so you can hack into all devices and disable them. Communication can be disabled by locking everyone out of the comm system, radars can be disabled or made to lie. Mobile devices can be disabled or locked out, or made to be a spy network.

Answer 4

Use conventional fusion bomb/s high in the atmosphere or analouges to the van allen belts is the best option by my opinion. You could you the power produced by you facility to mess with the star's magnetic field to cause a coronal mass ejection you would do this by creating electromagnets in orbit of the star powered by solar or energy beamed by your plant to cause magnetic reconnection by positioning it agianst the grain of the star's magnetic field.