Disable the suspend button in your system
gsettings set org.gnome.settings-daemon.plugins.power button-suspend "nothing"
Revert to the default value
gsettings set org.gnome.settings-daemon.plugins.power button-suspend "suspend"
Disable the sleep button in your system
gsettings set org.gnome.settings-daemon.plugins.power button-sleep "nothing"
Revert to the default value
gsettings set org.gnome.settings-daemon.plugins.power button-sleep "hibernate"
Disable the hibernate button in your system
gsettings set org.gnome.settings-daemon.plugins.power button-hibernate "nothing"
Revert to the default value
gsettings set org.gnome.settings-daemon.plugins.power button-hibernate "hibernate"
Settings those options above does not disable the functions in your system, you can still use the cog wheel menu to hibernate / suspend, this only disables keyboard and other buttons you might have in your computer.