The telecommunication system is one of the most important parts of the high voltage direct current(HVDC) transmission system，since its operation status directly affects the control and protection systems. In this paper，the protection components which would be affected by faults of the telecommunication system were introduced first; then based on operation examples，the defects of using the equipment status of another station as the opening or locking conditions of some protection systems were analyzed，and some useful suggestions were discussed. At last, it was explained that attention should be paid to the backup protection when the HVDC system was shut down under telecommunication fault conditions.