In modern power systems, current transformers are like precise electrocardiographs, continuously monitoring the vital signs of power grid operation.
This measuring device based on the principle of electromagnetic induction accurately converts thousands of amperes of current into standardized 1A or 5A signals, providing reliable data support for relay protection, power metering and system monitoring.
1. Core technical principle
The core structure of the current transformer consists of a closed iron core, a primary winding and a secondary winding.
When the measured current passes through the primary side, an alternating magnetic flux is generated in the iron core, and a precisely proportional current signal is induced on the secondary side.
This electromagnetic conversion process strictly follows the law of conservation of energy, and the secondary circuit always presents a short-circuit working characteristic.
The phase error is controlled within ±10 arc minutes, and the ratio error accuracy reaches 0.1 level, ensuring that the measurement data truly reflects the system status.
2. Engineering application scenarios
In smart substations, 0.2S-level high-precision
transformers support the accurate operation of the power metering system.
The relay protection device obtains the fault current in real time through the 5P-level protection transformer, and the action time error does not exceed 40ms.
In the field of new energy, the combined electronic transformer realizes DC side current monitoring in photovoltaic power stations, and can withstand 1500V DC voltage and 100kA short-circuit current impact.
The rail transit system uses open-type transformers, which can be installed and maintained without power off to ensure the uninterrupted operation of the subway power supply network.
3. Technical breakthrough direction
The core saturation problem has spawned nanocrystalline alloy core materials, whose saturation magnetic density reaches 1.25T, which is 60% higher than that of traditional silicon steel sheets.
Composite insulation technology enables the equipment to work stably in extreme environments of -40℃ to +70℃.
The electronic transformer based on Rogowski coil breaks through the traditional electromagnetic limitations and realizes ultra-wideband measurement of 0.05Hz-1MHz.
The optical current transformer uses the Faraday magneto-optical effect to completely solve the problem of electromagnetic interference and show unique advantages in UHV DC projects.
From mechanical to electronic, from electromagnetic principle to optical sensing, the technical iteration of current transformers has always been in sync with the development of the power industry.
In the new era of energy Internet and digital substations, intelligent sensor units integrating 5G communication and edge computing technologies are redefining the boundaries of current measurement and laying the foundation for the perception of building a new power system.
