Are you using any of the 1x slots with cards already?

Why not switch to onboard graphics run by the cpu?

well I lived some time ago in the place that had similar as you described problems with electricity
and they only way to solve that problems was to by stabilizer - these thing you can but for different power
they are working from 145V  to 260V input, and give stable 220+-10V output

find one for 10-15KVA - that's the one you need and your problem with electricity will vanish and you'll be able to use normal power supply

Instead of trying to find a server PSU with those specs maybe you should consider upgrading your electrical circuitry. As the above poster described:

You are going to have a hard time finding one.  Power(watts)=Volts*Amps  so... 2400 watts divided by 120v would be 20 amps.  Most household electrical circuits on 120v are on 15 amp breakers.  You should really only use 80% of a circuit, so the maximum you should put on a 15 amp breaker would be 1440 watts at 120 volts.

This is why 2400 watt PSUs will only work on 220-240V.  The wiring is a much lower gauge, which means it can handle more current (amperage), and thus can handle the higher wattage.  Plus 240V circuits are usually on larger breakers to accommodate the larger wattage and amperage.

Powered USB risers use ~45-50W each. A SATA connector is rated for 54W, which is near the limit and a concern because of the constant draw at near the limit on the connector from a mining rig. That being said, many like BBT advocate the Sata to 6-pin connector included with risers is a heavy duty connector that can handle the load without a problem. To be safe, I use dual sata to 6-pin adapters that spread the load over two connectors instead of one.

https://www.aliexpress.com/item/Deconn-SATA-15-Pin-Male-to-PCI-Express-6-Pin-Dual-Video-Card-Adapter-Cable/32584991290.html

There are also dual molex to 6-pin connectors.

https://www.aliexpress.com/item/4Pcs-High-Quality-2-x-Molex-To-PCI-E-Power-Adapter-4Pin-4-Pin-6-Pin/32759205876.html

I use 6-pin PCI-E risers. Three thicker wires that are designed to spread a higher 12V load instead of two used by molex and sata connectors. The 6-pin risers also use four capacitors for a more stable current flow compared to the three used by the molex and sata risers. The good ones also come with a voltage regulator to prevent spikes.

Just remember to never power more than two risers per SATA or 4-pin Molex PSU cable MAX. Using more more than that, you are overloading the rail and can damage the PSU, cables, connectors or all of them.

You don't have to use the adapter on the 6 pin risers.  You just plug the 6 pin power cable from the PSU directly into the riser.  The adapters are only included as a convenience.

WHERE can I buy one?