为解决非本征光纤法布里-珀罗(Extrinsic Fiber Fabry-Perot Interferometor, EFPI)在电力变压器内体绝缘安装困难且易损坏的问题, 设计了高灵敏度的EFPI传感器, 提出采用油腔结构的变压器油箱壁外置式安装方法。在阐述EFPI传感和液气介质下膜片振动原理的基础上, 分析了传感器检测灵敏度与其法-珀腔膜片尺寸的关系, 设计EFPI传感器法-珀腔膜片尺寸并制备传感器。然后, 设计外置油腔耦合结构, 采用压电陶瓷(Piezoelectric, PZT)声发射传感器构建EFPI传感器性能测试系统, 测得EFPI传感器的幅频特性和检测灵敏度。最后, 使用板-板电极和变压器实体模型搭建局放检测系统, 外置EFPI传感器与PZT传感器同时探测电极局放信号。实验结果表明: EFPI传感器的一阶固有谐振频率为113 kHz, 静压灵敏度为7.5 nm/kPa, 外置油腔耦合结构EFPI传感器局放超声信号的检测灵敏度高于传统的PZT传感器。外置结构可有效保护传感器膜片, 降低安装难度, 且避免了EFPI传感器置于变压器绝缘高场强度区域带来的安全隐患。

Extrinsic fiber Fabry-Perot Interferometer (EFPI) sensors are difficult to install and can be damaged easily in the internal insulation of power transformers. To address this issue, a high-sensitivity EFPI sensor was designed in this study, following which an external method was proposed to install the EFPI with the oil cavity on the transformer tank. On the basis of the principle of EFPI sensors and diaphragm vibration in gas-solid media, the relationship between the EFPI detection sensitivity and its diaphragm size was first analyzed, following which the high-sensitivity sensor size was designed and manufactured. Subsequently, the cavity oil structure of the external installation was designed. The Piezoelectric ceramic Transducer (PZT) was used to build an EFPI testing system, using which the amplitude-frequency characteristics and detection sensitivity were analyzed. Finally, a board-to-board electrode and transformer model were employed to build a PD detection system, and the external EFPI and PZT sensors were enabled to detect the PD acoustic signals synchronously. The experimental results show that the first-order natural resonance frequency of the EFPI sensor is 113 kHz, and the static pressure sensitivity is 7.5 nm/kPa. Moreover, the external EFPI sensor is significantly more sensitive than the PZT sensor. The external EFPI structure is effective for ensuring protection of the sensing diaphragm, and its installation is considerably less difficult. Furthermore, potential risks are prevented when the EFPI sensor is placed in the high-voltage field strength area.