Sony has announced that there is PSN Maintenance scheduled for Thursday 05th September from 20:00 until Thursday 05th September 22:00 BST.
For the duration of the maintenance you will be unable to log into the PlayStation Network, Account Management and the PS Store. PS Home will also be unavailable.
Some users may be able to sign in however, the services listed above will still be unavailable during the maintenance window.
There may be some additional downtime after the maintenance period for testing purposes.