Electromagnetic current mutual inductor iron core on-line demagnetizing method

Abstract

In the method, unbuilding device is connected to subsidiary side of electromagnetic type current transformer and is cascaded to load. The unbuilding device is composed of bi-directional thyristors, controlling circuits, and current transformer. Based on condition of current in circuit, or at fixed time (such as once per year), operation personnel controls the device: short circuit current passing through the unbuilding device starts it up automatically so as to remove residual magnetism on line totally.

Description

technical field [0001] The invention belongs to the technical scope of transformer manufacturing, in particular to an online demagnetization method for an electromagnetic current transformer iron core. Background technique: [0002] Electromagnetic current transformers are mainly used for energy metering and relay protection in power systems, and their accuracy is of great significance to power economy and operational reliability. Transformer manufacturers have done a lot of work to ensure their accuracy. But there is no effective method to solve the influence of remanence on the working characteristics of current transformers. Wang Xiaoqi, Guo Keqin, Yao Min, and Shi Xiao reported in the literature: "The Influence of Remanence on the Accuracy of Current Transformers. Transformers, Issue 06, 1996, 5-9", when a short-circuit fault occurs in the power system, the current transformer will Large residual magnetism is generated, and for a current transformer of class 0.2, the a...

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Problems solved by technology

[0004] The existence of residual magnetism will affect the working characteristics of the current transformer and will prevent accurate measurement

Larger residual magnetism will even affect the normal operation of the relay protection device, and even cause malfunction

[0005] In order to suppress the remanence, there is a method to use ferromagnetic materials with small coercive force, such as permalloy or amorphous materials, but the price of these materials is high, which will double the manufacturing cost of the transformer

In addition, someone proposed to open a small air gap on the iron core, but this method will increase the magnetic flux leakage and reduce the measurement accuracy, and it is not convenient to manufacture.

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