I'll start off by saying that I know this not a recommend practice.
I'm looking to build a regulated power supply that can supply 1200VDC at 300mA. The supply consists of a transformer, xenon tube rectifier bridge, a choke input filter (5H), and the pass tubes of the regulator.
I have found 315mA 1000VDC fuses, but have been unable to find any fuses of a higher voltage rating below 2.5A. Being that the maximum fault current isn't very high (limited by the transformer windings, rectifier impedance, choke winding, and pass tubes), would fuses in series be effective?
From what I can see even if one were to blow and maintain an arc, the second fuse would blow shortly. The two should then be enough of an arc gap to extinguish it, right? The 1000V fuses are the ceramic shell sand filled type, and since I'd only be exceeding the voltage rating slightly I'd be surprised if the first fuse didn't quench the arc itself, but I'd rather be safe.
In the event both fuses fail to break the circuit, it would inevitably blow the mains fuse. Also if anyone knows where to get fuses rated for a higher voltage at that current and they're not obscenely expensive I'm all ears.