How to wipe OS partition in TWRP? Operating system partition can be wiped in order to reinstall a broken ROM installation for example, personal files will be left intact. What is the correct partition to wipe?
Partitions for OnePlus One in TWRP (excluding cache and USB OTG):


system
data
internal storage
You should go for advanced wipe and choose:
-DalviK/ART Cache
-System
-Data
-Cache
And don`t format:
-Internal Memory
-Sdcard