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

测量高压通常需要额外的设备，如容性或阻性分压器与电压互感器相结合。这些传统的技术在频宽、绝缘和动态特性的非线性等方面存在一定的局限性。本研究开发了一种新型的Pockels电光传感器，它可以直接测量高压，而不需要任何额外的分压器。它采用纵向调制排列的光纤波克尔斯晶体。主要研究结果如下：1。制备了直径为0.9 mm、长为40 mm的Bi_4Ge_3O_<12>(BGO)纤维口袋晶体。该传感系统由光纤BGO晶体、632.8nm He-Ne激光器作为光源、通信链路大芯光纤、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 kV，对应传感器系统的最大可测电压。其数值比理论预测值大5倍。这种特性被认为对测量高压是有用的。测试了传感器系统在直流、交流、雷电冲击和阶跃波形下的性能，电压最高可达50 kv。使用传统的Pockels传感器在闪电脉冲测量的尾部观察到一个在数百kHz范围内的振荡分量，用现有的传感器系统成功地消除了。该传感器系统在上升时间内响应3 ns的快速阶跃电压，对应于116 MHz的频率带宽。最后，实验结果表明，该传感器在直流到100 MHz以上的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.