Keep Awake is a free Chrome extension that will prevent your Chromebook from going to sleep. It is available in the Chrome Webstore. It will temporary disable the power management on your Chromebook. It adds an icon in the browser at the upper right hand corner that will give you the following options:
The sun icon will prevent your Chromebook from going into sleep mode. It will keep your screen on.
The moon icon will allow your Chromebook to behave the same way as if you did not install the extension. Meaning, after a few minutes of inactivity, your Chromebook will go into sleep mode.
The sunset icon will allow your Chromebook screen to be on, but it will eventually dim and go into sleep mode. The network connections will remain active.
All you have to do is click on the icon and it will toggle through the options. Enjoy!