Due to the advantages of LCC-VSC (line-commutated converter-voltage source converter) three-terminal DC technology in terms of new energy consumption

long-distance transmission

reliability and economy

China has successively constructed a number of hybrid DC transmission projects. However

there is very little research on the protection principles of this topology. And there are problems

such as different control strategies

different line boundary elements

and different operating time requirements. A technology based on the Gini impurity of line mode voltage is proposed as the main protection scheme. This protection principle uses Gini impurity to describe the degree of confusion of fault information caused by boundary elements and further identifies internal and external faults. Finally

different faults are set to verify the reliability and superiority of the proposed protection scheme. A large number of results show that the protection scheme based on Gini impurity can identify the fault type within 1ms under an interference of 600

$\Omega$

resistance and 10dB noise.