Does your server have a good uninterrupted power supply (UPS)?
First let me explain the benefits of a UPS as we often find they are commonly overlooked or the wrong one is provided. The purpose of a UPS is to provide emergency power to your desktop or server (or other device) preventing important work from getting lost. When the power is lost the batteries in the UPS kick in generally providing 5-15 minutes of power. This is normally enough time for power to be restored or for you to shut the device down gracefully.
Be wary of using cheap models as you really get what you pay for with a UPS and it maybe designed for a desktop rather than a server. I recommend you get a line interactive UPS which provides better protection that a standby UPS by tolerating continuous over or under voltage. If you run a 24/7 business where you need to switch to a generator then you should use the more expensive online UPS which provides a layer of insulation from power quality problems.
Most UPS have a led light to show the state of the batteries which should be replaced every couple of years. You might want to test the UPS and see if it holds your system up which you can do by unplugging the UPS from the wall. Do you have a small LCD monitor plugged into a UPS so you can see when you need to shut your server down?