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IT Bushing Current Transformer (BCT) is a key device for current measurement and protection in high-voltage power systems. Its working principle is based on electromagnetic induction. At the same time, it has unique advantages in high-voltage scenarios due to its integrated design with high-voltage bushings.
Core working principle: precise application of electromagnetic induction
The working mechanism of the bushing current transformer follows Faraday’s law of electromagnetic induction. The specific process can be divided into four key steps:
Primary conductor: the high-voltage bushing itself
Unlike traditional current transformers, BCT does not require an independent primary winding. The high-voltage bushing is an insulating structure used to isolate the conductor from the ground barrier. It serves as the primary conductor, and the high-voltage current flows directly through the conductive rods inside the bushing. This design greatly simplifies the device structure.
Magnetic field generation: the “invisible effect” of current
When the current passes through the conductive rods of the bushing, according to Ampere’s law, an alternating magnetic field is generated around the conductor, and the magnetic field strength changes synchronously with the current size. The larger the current, the stronger the magnetic field, providing a “signal source” for the subsequent induction process.
Secondary winding: “converter” of the magnetic field
The secondary winding of BCT is wound on the outside of the bushing or in the built-in iron core, with far more turns than the primary winding of traditional CT. These windings act as “receivers”, tightly coupled with the magnetic field generated by the primary conductor, forming the core structure of electromagnetic induction.
Induced current: safe conversion of high voltage to low voltage
According to Faraday’s law, the alternating magnetic field will induce a low current (usually 5A or 1A) in the secondary winding, and this current is in a fixed proportion to the primary high voltage current (determined by the turns ratio). This conversion realizes the “safe translation” of high voltage current, allowing instruments and protection devices to directly use low voltage signals to avoid high voltage risks.
Unique advantages: the practical value of integrated design
Based on the above principles, bushing-type current transformers show multiple advantages in practical applications:
Space saving: integrated design with high voltage bushing, no additional installation space is required. Especially suitable for compact layout scenarios such as substations and switchgear.
Simplified installation: reduce the wiring and fixing steps of independent CTs, reduce construction complexity, and shorten the engineering cycle.
Improve safety: The winding and high-voltage parts are insulated and isolated by bushings, reducing exposed wiring and the risk of electric shock or short circuit.
Industry application: “Monitoring sentinel” of a high-voltage system
BCT is widely used in key nodes of high-voltage power equipment:
The high-voltage bushing of the transformer monitors the winding current in real time to prevent overload.
In switchgear (such as GIS combined electrical appliances), cooperate with protection devices to quickly respond to faults;
High-voltage line terminals ensure that the transmission current is stable within a safe range.
Quality choice: Hewei’s technical strength
Among current transformer manufacturers, Hewei focuses on transforming the above principles into reliable products. The wall bushing current transformer it produces strictly follows the accuracy requirements of electromagnetic induction to ensure that the error of current conversion is controlled within the industry standard range (usually 0.2 or 0.5). Meeting the needs of high-precision measurement and protection.
At the same time, Hewei’s BCT design gives full play to the advantages of integration. High-strength insulating materials (such as epoxy resin) are used to adapt to high-voltage environments, and the magnetic field coupling efficiency is improved by optimizing the winding layout, which not only ensures the stability of electromagnetic induction but also strengthens the durability of the equipment under extreme temperature and humidity. It provides solid support for the safe and efficient operation of the power system.
Summary
The bushing-type current transformer cleverly solves the measurement problem of high-voltage current through the design of “using a bushing as a primary conductor and electromagnetic induction as the core”. The simplicity of its working principle and the professionalism of its application scenarios make it an “invisible guard” of modern power systems. Choosing products from Hewei can better transform the advantages of this principle into reliability in actual operation, making each current monitoring accurate, safe, and efficient.
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