Trial Development of New Optical High Voltage Sensor Using Pockels Fiber Crystal

高电压的测量通常需要额外的设备，如电容式或阻性分压器与电压互感器相结合。这些传统的测量技术在频带、绝缘和动态非线性等方面都有一定的局限性。本研究开发了一种新型的Pockels电光传感器，不需要任何额外的分压器，直接应用于高压测量。它使用纵向调制排列的光纤普克尔斯晶体。主要研究结果如下：1.生长了直径0.9 mm、长40 mm的光纤Pockels晶体Bi4Ge_3O_(12)。该传感器系统由光纤BGO晶体、632.8 nm He-Ne激光器为光源、通信链路中的大芯光纤、PIN光电二极管探测器和高压SF_6气体绝缘容器组成。测得的半波电压为162千伏，相当于传感器系统的最大可测电压，比理论预测值高出5倍。这一特性被认为对测量高电压很有用。对传感器系统的直流、交流、雷电冲击和阶跃波形进行了测试，电压最高可达50kV。该传感器系统成功地消除了传统Pockels传感器在雷电冲击测量尾部观测到的数百kHz范围内的振荡分量。传感器系统在上升时间响应3 ns的快速阶跃电压，对应的频率带宽为116 MHz。实验结果表明，该传感器在直流到100 MHz以上的较宽频率范围内具有平坦的频率响应。

Measuring of the high voltages generally needs extra devices such as capacitive or resistive dividers in combination with voltage transformers. These conventional techniques have some limitation in frequency bandwidth, insulation and nonlinearity at the dynamic behavior.In this research a new Pockels electro-optic sensor applied directly to measure high voltages without the aid of any additional voltage divider are developed. It uses a fiber Pockels crystal in a longitudinal modulation arrangement. Main results obtained are as follows :1. A fiber Pockels crystal of Bi_4Ge_3O_<12>(BGO), which is 0.9 mm in diameter and 40 mm in length, has been grown. The sensor system consists of the fiber BGO crystal, He-Ne laser of 632.8nm as a light source, large core optical fibers in communication link, a PIN photodiode detector, and a high voltage SF_6 gas insulated vessel.2. The measured half-wave voltage, which corresponds to the maximum measurable voltage of the sensor system, as 162 kV.Its value is 5 times lager than the theoretically predicted value. This characteristic is considered to be useful for measuring high voltages.3. The performance of the sensor system was tested for dc, ac, lightning impulse and step waveform applied voltages up to 50 kV.4. An oscillatory component in the range of hundreds kHz, which was observed in the tail part of the lightning impulse measurements using conventional Pockels sensors, is successfully eliminated with the present sensor system.5. The sensor system responds to a fast step voltage of 3 ns in rising time which corresponds to a frequency bandwidth of 116 MHz. Finally, the experimental results show a flat frequency response of this sensor in a wide frequency range from dc to more than 100 MHz.