Method for measuring direct current magnetic bias current of neutral point multi-point grounding power transformer

Abstract

The invention provides a method for measuring the direct current magnetic bias current of a neutral point multi-point grounding power transformer, which comprises the following steps of: 1, cutting sampling flat steel with the same length from each grounding flat steel as a sampling resistor, and applying a current source to two ends of one of the sampling flat steel; 2, connecting voltmeters to two ends of the cut length of each sampling flat steel, and sampling voltage signals of the sampling flat steel; and 3, enabling the current source to apply currents of different magnitudes twice, enabling each piece of sampling flat steel to respectively extract voltage signals under the working condition of the currents twice, obtaining the actual resistance value of the sampling resistor through conversion under the condition of considering the inherent grounding current of the neutral point through the known current and voltage signals, and then measuring a direct-current magnetic bias current signal flowing through each piece of flat steel. The method can accurately measure the direct-current magnetic bias current of the neutral point of the power transformer when multiple grounding flat steel is grounded, is suitable for field detection and on-line monitoring, and has the advantages of being free of temperature drift and capable of being calibrated on line compared with a traditional Hall sensor.

Description

technical field [0001] The invention relates to the technical field of electrical parameter measurement in a power system, in particular to a method for measuring DC bias current of a neutral-point multi-point-to-ground power transformer. Background technique [0002] When the DC transmission system operates under the unbalanced condition of single pole or bipolar pole, the DC current is injected into the ground through the DC grounding pole, and the AC transmission system forms a parallel circuit with the ground through the neutral point of the grounded transformer, the transmission line and the ground wire of the overhead line. Shunt the DC current into the ground, and the shunt size can reach tens of amperes. This phenomenon is called DC bias phenomenon, which will distort the excitation current of the transformer, saturate the iron core, and affect the magnetostrictive properties of the iron core silicon steel sheet, resulting in The vibration and noise of the transforme...

AI Technical Summary

Problems solved by technology

[0005] Aiming at the problem that the neutral points of power transformers in substations and power plants are connected to the ground at multiple points, and the measurement results of the traditional resistance sampling DC bias current measurement method are distorted, the present invention proposes a method suitable for multiple points of neutral points connected to the ground (such as double-grounded flat Steel, four-ground flat steel and other multi-input locations) DC bias current measurement method for power transformers

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