Same place it's always been, and as noted, it's in the power profile.
Control Panel, Power Options. Then, depending on whether you're wanting to tweak the power plan you're currently using, in which case activate the Change plan settings link next to the plan you've currently got in use, then activate the Change Advanced power options link and find the Hard Disk entry.
If you're trying to create a whole new power plan then hit the Create a power plan link instead and go through the process.
As britech said above, in the "Change Advanced power options" link, double click "Hard disk"> , DC Turn off the Hard disk and then, at Settings (minutes) set the wait time settings, but there is no never setting, but you can choose up to 10,000 minutes Windows 10 will wait before it turns off your hdd.