The DC line protection should be configured according to the characteristics of the specific project. On the basis of an analysis of the characteristics of Lusheng high voltage direct current (HVDC) project and the influence of the control system on the protection

the line longitudinal differential protection is selected as the main DC line protection and low voltage protection as back up protection. Meanwhile

in consideration of the existence of the time delay of telecom between two converter stations

protection false trip may occur because of asynchronous comparison of line terminals current. In order to eliminate the impact of the time delay

a method of compensating for the channel delay is proposed. With this method

the low voltage protection as the backup protection will act in case the telecom is interrupted and longitudinal differential protection is out of work. The reliability and sensitivity of line protection have been verified by real-time digital simulator (RTDS) based simulation tests.