Device and method for detecting multipoint earthing of voltage transformer for electric system

Abstract

A device for detecting multipoint earthing of a voltage transformer for an electric system comprises a CPU main controller, an analog-digital conversion circuit and a switch control circuit. A voltage transformer secondary neutral line N600 penetrating into an opening current transformeris connected with a ground point, and output passes through a first filter amplifying circuit to the analog-to-digital conversion circuit. A ground point penetrates through a current transformer to be connected with one end of a sampling resistor Rv, output passes through a second filter amplifying circuit to reach the analog-to-digital conversion circuit, the other end of the sampling resistor Rv is connected with a plurality of branch circuits, and switches and resistors are in series connection with the branch circuits which are correspondingly and externally connected with an A-phase bonding post of the voltage transformer for electricity use. The two ends of the sampling resistor Rv further outputs a 0-5V voltage signal to the analog-to-digital conversion circuit through an isolation amplifying circuit. The invention further relates to a method for detecting multipoint earthing faults of the voltage transformer for the electric system. According to the device for detecting multipoint earthing of the voltage transformer for the electric system and the method for detecting multipoint earthing faults of the voltage transformer for the electric system, whether the multipoint earthing faults of many voltage transformers exist can be accurately detected in time, and the multipoint earthing faults can be specifically located.

Description

technical field [0001] The invention relates to a detection device for a multi-point grounding fault of a voltage transformer in a power system. The invention also relates to a detection method for a multi-point grounding fault of a voltage transformer in a power system using the above-mentioned device. Background technique [0002] There are many transformers in power systems such as power plants and substations, and many transformers need to be grounded through the grounding grid. However, the ground grids of power plants and substations are not real equipotential surfaces, and there will be potential differences between different points. When a large ground fault current of a large primary device is injected into the ground grid, the potential difference will increase accordingly. If the PT secondary circuit is grounded at multiple points at different locations in the power plant and substation at the same time, the potential difference on the ground network will enter t...

AI Technical Summary

Problems solved by technology

If the PT secondary circuit is grounded at multiple points at different locations in the power plant and substation at the same time, the potential difference on the ground network will enter the PT secondary circuit, and the voltage waveform of the relay protection may be distorted or the measurement data may be incorrect. Causes incorrect action of impedance and directional elements

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