An Improved Current Differential Protection Scheme on Non-Homogeneous Transmission Lines Considering Fully Distributed Parameter Model and Line Asymmetry

Current differential protection is widely adopted in the high voltage AC transmission line with high sensitivity and selectivity. The capacitive charging current in long distance nonhomogeneous transmission lines with overhead lines and underground cables may be too large to be ignored. Therefore, accurate charging current compensation must be carefully considered. In this paper, an improved current differential protection is proposed for non-homogeneous transmission lines. The method can fully compensate the capacitive charging current by fully considering the distributed parameters and at the same time the line asymmetry. Numerical experimental results demonstrate that the proposed protection method can accurately compensate the charging current. In addition, compared to the legacy current differential protection methods, the proposed method presents improved dependability during internal faults, and improved security during external faults and other system transient.