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，例如电容或电阻分压器与电压互感器的组合。这些传统的技术在频带宽度、绝缘性和动态特性的非线性等方面存在一定的局限性，本研究开发了一种不需要附加分压器而直接用于高电压测量的新型Pockels电光传感器。它采用光纤泡克尔斯晶体的纵向调制安排。取得的主要结果如下：1。生长<12>出直径0.9mm、长40 mm的Bi_4Ge_3O_（BGO）光纤Pockels晶体。该传感器系统由BGO光纤晶体、632.8nm He-Ne激光器、大芯径光纤通信链路、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，对应于传感器系统的最大可测电压，其值是理论预测值的5倍。这个特性被认为是有用的测量高电压。3.传感器系统的性能进行了测试，直流，交流，雷电脉冲和阶跃波形施加电压高达50千伏。使用传统的普克尔斯传感器在闪电脉冲测量的尾部观察到数百kHz范围内的振荡分量，本传感器系统成功地消除了该振荡分量。传感器系统响应于上升时间为3 ns的快速阶跃电压，其对应于116 MHz的频率带宽。最后，实验结果表明，该传感器在从直流到超过100 MHz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.