A kernel power error message in windows can relate to two things.
The first is and indicator that your power supply unit fitted in your tower based system is not up to the job of providing enough power to all parts of the computer such as the motherboard, connected hard disk drives or Cd/Dvd drives.
And the R9 270x card you have fitted in the pci-e slot of the motherboard for your graphics.
The error will pop up for example when you begin to run a game because when the video card driver switches to 3d mode and begins to use the Gpu of the 270x card more power is required from your PSU in your system.
It can also suggest that based on the mother board you have that you may have missed out a connection for a 12v supply from the PSU to the motherboard or based on the graphics card you use and it`s power requirements when running under a gaming load that extra 12v that may be connected to the graphics card it`s self from the psu you have also is not connected.
You should double check all of the points or things to check listed above.
If it turns out you have all the power connected from your PSU to the motherboard, and graphics card fitted in the pci-e slot of the mother board.
Then you are looking at a cheap power supply that cannot provide what is stated it can output in wattage and amps of the 12v,5v, or 3.3v power rails, or it has a fault internal with the power supply unit.
The last thing to try is to change the power and sleep mode options that can be found by entering the bios menu of the motherboard you have, go to the Acpi power section option and set your power mode to at least S1/S3 mode to avoid the errors in windows. make sure you save the changes before you exit your bios once set.
Next go to the power settings within windows and set the mode you wish.
To avoid the error you may be best setting the power plan to balanced, or change how devices consume power by using the advanced setting of the power scheme options. often you can get a power kernel error due to the fact that a bit of hardware has powered down under the set power saving options and fails to power up right when windows signals it to do so via the Acpi settings and the mode set in your bios it is important to set the right S mode as said to at least S1/S3 mode so devices respond and power up right if power saving in set up. And why you can get as said a power kernel error report from windows.
Basically a device failed to power up on windows signaling it from power saving mode or hibernation/ low power mode ok.
Set these and the error will most likely stop for you ok.