Research On DC Incremental Protection Of Feeder Power In Traction Power Supply System

The high-speed railway traction power supply system provides power protection for electric locomotives/EMUs,which is of vital importance to the safe and reliable operation of high-speed railways.The faults of the fully parallel AT traction network are mainly short-circuit faults and disconnection grounding faults.When the fault occurs,impedance protection as the main protection of the feeder of the traction substation is generally used for action tripping.However,when a high-resistance ground fault occurs,the measurement impedance increases and the short-circuit current decreases,causing the impedance protection to refuse to trip,which will bring huge hidden dangers to the safe and stable operation of the traction power supply system.As the back-up protection of impedance protection,current increment protection plays an important role in the case of high-resistance ground faults and wrong-phase short-circuit faults.In actual operation,a high-resistance ground fault occurs when multiple electric locomotives/EMUs in the power supply arm take current at the same time,or a short-circuit fault occurs at the end of the traction network,the current increment is small,which may cause the current increment protection to fail;When a electric locomotive/EMUs enters the power supply arm through the neutral zone,and a electric locomotive/EMUs starts in the same power supply arm,the current increase is relatively large.If the harmonic blocking element is in a critical state,the current increase may malfunction.Based on the idea of DDL protection of the subway DC traction power supply system,this paper simulates the normal operation of the fully parallel AT traction power supply system and the different working conditions of the traction network short-circuit fault,disconnection grounding fault and out-of-phase short-circuit fault based on the RTDS real-time digital simulation platform.Collect instantaneous voltage and current signals.Using the single-phase generalized instantaneous power theory based on Hilbert transform,the instantaneous active power is calculated and the DC component of the power is extracted.Comparing the changes of the active power DC increment under different working conditions,it is analyzed that the active power DC increment can be used as a characteristic value to distinguish between normal operation and traction network failure,and the principle of power DC increment protection is proposed,and the setting value and equation of action are also given.The feasibility and rationality of power DC incremental protection are verified by simulation.Compared with current incremental protection,power DC incremental protection improves the reliability and sensitivity of feeder protection.