实验室大量试验结果表明,使用超声阵列传感器对变压器进行局部放电检测时,核心是选择合适的波达方向(DOA)估计算法.提出一种改进的FastDOA算法进行变压器局部放电超声阵列信号的测向,该算法在传统FastDOA的基础上增加一个扩展系数来构造不同阵列孔径的虚拟阵列,然后利用真实谱峰的大小、位置不变,伪峰大小、位置随扩展系数改变的原理,对各虚拟阵列得到的估计谱值进行加权平均以减小伪峰的影响,有效提高测向精度.利用MATLAB对其进行仿真,结果显示该算法的测向误差在2°以内,与传统算法最大误差超过10°相比,具有更好的稳定性.在实验室搭建局部放电测向平台,10组试验数据表明该算法的误差均在3°以内.%Lab experiments show that the appropriate algorithm of DOA(Direction Of Arrival) estimation is the key of transformer PD(Partial Discharge) detection by ultrasonic array sensors. A modified FastDOA algorithm is proposed for transformer PD orientation with ultrasonic array signals,which adds an expansion coefficient to traditional FastDOA algorithm to form several virtual arrays with different aperture sizes. Because the size or position of real peak is consistent while that of virtual peak changes along with the change of expansion coefficient,the weighted average of virtual array spectrums is calculated to restrain the virtual peaks and increase orientating accuracy. Results of the simulation with MATLAB show that,with the orientating error within 2°,the proposed algorithm has a better stability,while the maximum error of the traditional method is bigger than 10°. A PD orientation test platform is built in lab and ten groups of experimental data show the orientating errors are within 3°.
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