Rail transit power supply system negative ground limiting protection device

Abstract

The invention discloses a rail transit power supply system negative ground limiting protection device, and belongs to the technical field of rail power supply. The device comprises a negative ground voltage limiting module, a negative ground voltage and current detection module, an intelligent control module and a thyristor cut-off control module; the negative ground voltage limiting module comprises a first contactor and a thyristor module which are connected in parallel, and when the potential difference between a negative return rail and the ground exceeds a specified voltage value, the thyristor module and the first contactor are conducted; the negative ground voltage and current detection module is used for detecting current and / or voltage between the negative return rail and the ground and uploading the current and / or voltage to the intelligent control module; the intelligent control module is used for receiving the voltage detected by the negative ground voltage and current detection module and controlling the thyristor cut-off control module to immediately cut off the thyristor module after the first contactor is closed; and the thyristor cut-off control module is used forimmediately switching off the thyristor module after the thyristor module is switched on in the forward direction. According to the invention, stray current increased due to continuous conduction of the thyristor can be reduced, and the service life of the thyristor is prolonged; small frame leakage current is discharged to a negative electrode, and stray current is prevented from flowing into theground.

Description

technical field [0001] The invention belongs to the technical field of rail power supply, and in particular relates to a negative ground limit protection device for a rail transit power supply system. Background technique [0002] The contactor is an important component of the rail potential limiting device to realize the protection function of personnel and equipment. It is installed between the negative return rail (hereinafter referred to as the rail) and the earth. Its function is that when the voltage of the rail to the ground exceeds or equals the set value, Quickly connect the rail to the ground to ensure the "zero" potential of the rail. [0003] The traditional rail potential limiting device includes a thyristor, a DC contactor, a voltage measuring element, and a PLC logic control module. The voltage measuring element and the current measuring element are used to detect the voltage between the rail and the earth, and upload it to the controller for display. The DC ...

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Problems solved by technology

[0005] 1. In order to ensure that the pressure is released to zero, and to avoid the impact of the thyristor being turned on repeatedly due to excessive voltage, it can only be designed to be locked (that is, locked) after the DC contactor is closed. At this time, you need to manually press Reset button resets contactors, thus losing remote control functionality

[0006] 2. If the thyristor cannot be turned off immediately during the bypass process, it will increase the conduction time and seriously damage the life of the thyristor. With the continuous use of the thyristor, the DC contactor will be turned on and the negative ground voltage will return to zero, and the thyristor will continue to operate. conduction phenomenon, increasing the stray current

[0009] The frame protection device guarantees the damage to the equipment when the positive electrode is short-circuited to the frame, but because the leakage current of the frame cannot be guaranteed to flow into the ground, the underground metal objects are electrochemically corroded due to the leakage current of the frame

In the initial stage of rail transit operation, the insulation performance of the rails to the ground is good. When the frame leakage fault occurs in the DC equipment of the traction substation, the current flowing through the current measuring element is very small, and the current element of the frame protection device does not operate, and the flow continues The frame leakage current flows into the ground, causing immeasurable electrochemical corrosion

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