After you deploy Group Policy power management settings or preferences that contain the Specify the system sleep timeout or Sleep after setting, connected standby systems that are running Windows 8.1 don't sleep or hibernate at the configured time.
Connected standby systems use a different setting to control sleep and hibernation than is used by systems that don't have connected standby capability.
To control the sleep setting time-out for connected standby systems, you must configure the Turn off the display setting.
Connected standby–capable systems have a single, unified function for controlling the display-off and sleep time-out settings. Whereas traditional systems use separate settings to control when the display turns off and when the computer goes to sleep. Therefore, on a connected standby system, when you change the Turn off display after setting in the advanced power settings, the Put the computer to sleep setting is also changed, and vice versa.
Because connected standby devices have minimal power management settings, other Group Policy settings that involve power policies may not apply or function as expected. Settings that do not work on connected standby systems include the following:
Reduce Display Brightness
Specify the system hibernate timeout
Turn off Hybrid Sleep
For more information, see the Introduction to connected standby white paper.