Protection and control system for cophase supply traction substation

To feed electric train, the structure of traction power supply system is very different from utility grid. The single-phase traction loads result in some problems, such as negative sequence, harmonics, reactive power and crossing neutral sections. Based on the existing traction power supply system, the active power filter is used to construct cophase traction power supply system. It not only eliminates neutral sections near traction substations but also compensates harmonic current and reactive power. In a perfect operation condition, seen from the HV side, single-phase and nonlinear traction load is approximately equivalent to three-phase symmetrical resistance load. The cophase power supply testing system is introduced in this paper. And also the protection and control functions for cophase traction substation are introduced. (6 pages)