基于有源光纤光栅阵列的局部放电声发射检测与定位技术

Partial Discharge Acoustic Emission Detection and Localization Based on Active Fiber Grating Array

针对现有光纤超声传感器复用系统光路繁琐、传感器无法实现多点同步测量等不足,该文提出一种基于有源光纤光栅(fiber bragg grating,FBG)阵列的局放声发射传感检测方法。通过抑制系统的弛豫振荡噪声、引入不平衡干涉仪和声光调制器将微小波长变化的检测转化为相位变化进行解调,使系统检测灵敏度明显提高;理论推导并验证非平衡干涉仪臂长差优化设置方案,使光纤超声传感阵列各传感元检测下限比压电陶瓷换能器(piezoelectric transducer,PZT)低17.1%~19.7%。在此基础上,开展变压器油中局部放电检测与定位实验。实验表明:在1000mm×1000mm×1100mm的油箱内定位精度小于40mm;对于变压器油中悬浮放电模型,有源FBG的局部放电检测起始电压比PZT低22.2%,可测放电量低24.0%。结果可为变压器油中局部放电提供一种高灵敏度的检测与定位方法。

Aimed at the existing shortcomings of the multiplexing optical fiber ultrasonic sensing systems, this paper proposes a detection system for partial discharge(PD) caused ultrasonic waves, which is based on active fiber bragg grating(FBG) array. The relaxation oscillation noise of the sensing system is inhibited. An unbalanced Mach-Zehnder interferometer(MZI) and an acousto-optic modulator(AOM) are introduced to detect phase variation of sensing light returned from the active FBG array. By using this method, the detection of tiny wavelength change is converted to phase variation, so that the detection sensitivity is obviously promoted. The relationship between the arm length difference of the MZI and the detection limit of the sensing system is theoretically discussed and experimentally verified. The proposed system performs a 17.1%~19.7% lower detection limit than that of piezoelectric transducer(PZT). On this basis, the partial discharge detecting and locating experiments in transformer oil are carried out, which shows the localization accuracy of PD is less than 40 mm in an oil tank. For floating discharges in the oil, the detected PD inception voltage of the proposed system is 22.2% lower than that of PZT, and the lowest measurable discharge quantity is 24.0% lower. A high-sensitivity detection and positioning method is provided for PD in transformer oil.