Short circuit faults in submodules can be identified by low-level internal protections. Faulty submodules can be replaced with spare submodules with least impact on continuity of the converter operation. However, faults such as groundings at arms cannot be rectified so easily without impacting continuity of the operation and required to locate quickly to minimize the downtime. The literature on practical fault discriminations techniques are rare. Can anyone who has come across such techniques comment ?