A grounding protection mode for a traction network of a DC power supply system with both positive and negative electrodes insulated

Abstract

The invention discloses a grounding protection mode of a traction network of a DC power supply system with both positive and negative electrodes insulated, which is mainly generated by a negative ground single conduction device arranged between a negative electrode bus bar and a grounding bus bar of a traction substation as a positive electrode of the DC power supply system. In case of short-circuit fault of ground (overhead ground wire, through ground wire, vehicle shell or running rail, etc.), a short-circuit return path is provided, and the DC feeder protection action corresponding to the traction substation with current variation characteristics is used to realize selective tripping. The DC power supply system is mainly composed of a rectifier unit of a traction substation, a DC switchcabinet, a traction network positive and negative pole, a negative ground single conduction device, and the like. The grounding system comprises a grounding grid, a substation grounding bus bar, an overhead ground wire of an overhead contact network (a special rail return power supply system), a through ground wire (a medium-and low-speed maglev traction power supply system), a grounding flat steel, and other grounding conductors or reinforcing bars. The invention can realize selective tripping when the DC power supply system has a positive electrode ground short-circuit fault.

Description

technical field [0001] The invention belongs to the technical field of rail transit, and in particular relates to a grounding protection method for a traction network of a DC power supply system in which positive and negative poles are both insulated. Background technique [0002] With the rapid development of rail transit, more and more urban rail transit lines have been built and operated in China, and many emerging cities are planning and preparing for the construction of urban rail transit projects. At present, the domestic urban rail transit traction power supply system adopts the running rail as the return rail, and also adopts the four-rail return method. Among them, the four-rail backflow method can fundamentally solve the leakage and corrosion problems of stray current during normal operation, but there are the following problems: [0003] The grounding protection of the existing DC power supply system with both positive and negative poles insulated adopts a voltag...

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Problems solved by technology

[0003] The grounding protection of the existing DC power supply system with both positive and negative poles insulated adopts a voltage protection method, that is, a diode and a high-impedance voltage relay or a voltage protection element is connected between the negative pole of the traction substation and the ground to short-circuit the positive pole of the traction network to ground fault protection, such as figure 2 As shown, because the impedance of the voltage measuring element of the negative-to-ground unidirectional conduction loop in this system is relatively large, when a positive-to-ground short-circuit fault occurs in the traction network, the DC feeder protection of the substation that reflects the characteristics of the current change cannot achieve selectivity action, but this voltage element initiates the tripping of all DC feeder circuit breakers in the traction substation

Since the measured negative-ground voltage of each traction substation on the entire line is not characteristically strong, if there is a single fault in the traction network, the voltage monitoring elements of multiple nearby substations will detect a voltage rise, and multiple substations All DC feeder circuit breakers will trip at the same time, so the voltage protection is not selective, and the fault affects a wide range

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