| With the obvious improvement of transmission capacitance and rated voltage in power system, conventional electromagnetic transformers have several drawbacks and have been already difficult to meet the need that network develop towards automation and digitized direction. The electronic transformer has become a new direction of transformers' development for its no saturation under fault conditions, high level insulation and broad range of measurement. This paper is about active electronic transformers:electronic current transformers based on Rogowski coils (ECT) and electronic voltage transformers based on capacitive voltage dividers (EVT).In the beginning, the facing problem of traditional electromagnetic transformers and the advantage of electronic transformers are introduced in this paper, the far-reaching impact electronic transformers on substation automation system are analyzed and the present actuality of electronic transformers is summarized. Then this paper introduces the definition of electronic transformers. Whether power supply is needed, electronic transformers are divided into active and passive electronic transformers. Active electronic transformer includes five parts:sensor head; high-voltage part data acquisition system; optical fiber transmission system; power supply system and low-voltage part merging unit. In this paper, high-voltage part data acquisition system, optical fiber transmission system and power supply system are researched, following:Firstly, high-voltage part data acquisition system is the highlight in active ECT/EVT system. In the third chapter, the paper researches every element including A/D conversion unit, low-pass filter, integrator and so on. Data acquisition system is composed of electronic components, so it need power supply. It is important to choose low power data acquisition. This paper chooses single-phase energy measurement IC ADE7569. Power system only needs 3.3V. Its overall power consumption current is only 5mA in full operation. At the same time, ADE7569 has a built-in 8052 MCU core, which can directly control the date acquisition, and simplify the circuit configuration.Secondly, optical fiber transmission system has many benefits such as large capacity, low loss, strong anti-interference ability. The optical fiber transmission system transmits date information collected from high-voltage part to the merging unit. The optical fiber transmission system has two functions. Firstly, it is used to transmit the measured current and voltage signals. Secondly, it is used to ensure electrical isolation between the high-voltage part and the low-voltage part, which can reduce the error. This paper describes that the optical fiber transmission system includes several components:optical fiber, optical transmitter, optical receiver. HFBR-1414 is used for the optical transmitter, while HFBR-2412 is used for the optical receiver. The optical fiber uses multi-mode glass optical fiber.Thirdly, power supply for those active electronic elements at the high-voltage part is a key technique in active ECT/EVT system. This paper discusses several methods of power supply and then adopts the method power supply was provided by laser. This paper describes the working characteristics of the key apparatus LD,photocell and DC-DC converter. It also deeply researches the drive circuit, protection circuit and temperature controlled circuit. ADE7569 has advanced intelligent battery management model. It has two power input interface. In addition to regular power supply interface to access external 3.3V, there is also a battery backup interface. When the external power supply can not provide power, it can automatically connect 3.7V battery power. In addition, the optical fiber transmission system needs 5V, which is also provided by the laser power supply system.
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