Always use a UPS for your rigs, especially in third world countries with sporadic current. A brownout or surge can do irrecoverable damage or worse start rig fires. Also use modern risers with voltage regulators for extra protection in multiple card rigs.
In my opinion, each rig should have it's own UPS in which you connect a 'bronze' quality or better power supply. With that setup you can rest assured your rig is powered and in the case of power failure, you have extra time to shut down correctly.
I hope your mining Monero, the difficulty is still low enough to make r7 240's profitable 🤣 ...
Monero Difficulty Watch