Pilot protection of HVDC power transmission lines based on variation characteristics of firing angle

There exists a matching delay between the traveling wave protection and the current differential protection, which leads to the lack of protection during the transient process of DC control. Based on the idea of control and protection combination, a new principle of pilot protection for HVDC power transmission lines is proposed by using the changing characteristics of the firing angle at two converter stations in the transient process of DC control after fault. In the protection, the cosine similarity criterion between the mean values of the firing angle changing rate of the rectifier and inverter stations and the firing angle varia-tion criterion with the fixed time interval are constructed to identify the internal and external faults. The simulative results of PSCAD/EMTDC show that the proposed scheme can identify the faults in the transient process of DC control with fast motion speed and strong ability to withstand transition resistance, and it does not need strict synchronization of data acquisition. Therefore, the proposed scheme can be used as a fast backup protection for HVDC lines. © 2020, Electric Power Automation Equipment Press. All right reserved.