[Radio Wrangler]

That should do the job, but you probably should try it out somehow, just to feel confident it will save your bacon if it ever has to.

Motorola did a crowbar trigger IC that you programmed with the ratio of two resistor values, but I can't remember the type number. It's academic if they aren't available anyway.

If you're designing a complete power supply, you can integrate the crowbar into it in ways that make it a lot less dramatic. In the one I did, I have the crowbar do two things. It opens the relay used for mains on/off, and it uses its thyristor to dump the charge in the reservoir capacitors directly. If I trigger it, there is a little click and I hear the mains switch relay release. It does mean that this supply needs a push on a start button to turn it on, but the whole lot integrates with a soft-start arrangement. When I next come across the circuit diagrams, I'll post them in this group.

David