Improved ground distance protection for cascaded overhead-submarine cable transmission system

This paper presents an improved distance protection algorithm for detecting ground faults in transmission systems with cascaded overhead-submarine cable segments. The mathematical core of the proposed distance protective function considers the charging currents of both overhead and underground cable segments. Hence, an accurate detection of the fault event van be realized. On the other hand, the proposed algorithm overcomes the non-homogeneity of the composite transmission systems, via updating the calculated impedance for faults in the remote section. For evaluation purposes, a detailed simulation is utilized for a real 400 kV Taba-Al-Aqaba inter-tie composite transmission using the ATPDraw program. However, developing the phasor computation and the distance relaying algorithm are processed in Matlab. The obtained results are analyzed and compared with the conventional core of the distance relaying function, where the results emphasize the efficacy of the presented distance scheme for composite overhead-cable lines.