Er, well, not just ANY bare capacitor, or random wiring, and certainly not a bank of defibrillator capacitors at full charge!!

IEC 61000-4-5 defines a maximum Class 4 of 4kV (into 2 ohms, 2kA) surge. The time constant into 2 ohms is about 28us (it's not really a time constant because an RLC circuit is used), so about 14uF is needed.

To get the open-circuit waveform, some series inductance and parallel resistance is needed. Resistance might be around 3 ohm, which means the 1.2us rise time (for this condition) needs around 2uH.

To get the short-circuit waveform, more series inductance is needed (though not much more), a total of double I guess. The extra parallel resistance means more capacitance will be needed, maybe 24uF.

In the two conditions, sqrt(L/C) is much less than the ESR of the loop thus formed, so it should have no undershoot (the standard allows for 30% phase reversal), and no need for diodes and stuff. A contactor is probably okay for switching the surge (it's over before the contacts can bounce open again), or thyristors of not too extreme ratings (but do turn them on **hard!**).

Tim