瞬时介质损耗因数的定义与数字化算法

Definition and Digital Algorithm of Instantaneous Dielectric Loss Factor

针对现有电气设备介质损耗因数数字化算法多须信号频率在若干采样周期内不变且须严格同步采样的状况,基于瞬时频率理论提出了一种瞬时介质损耗因数的定义与数字化算法,并给出了算法的理论基础。通过求解超定方程组,利用该算法可回归得到等效电路参数,从而算得瞬时介质损耗因数曲线。仿真与实验结果表明,在电网频率短时瞬变的非平稳信号下,该算法可准确跟踪电网频率并回归出电路参数,且不受传统算法必须满足的前提条件约束,亦无需考虑同步采样和电网谐波的影响。该算法对监测数据的处理也更为灵活,便于应用数理统计方法实施进一步的诊断分析。

Among the digital algorithms presently available for on-line monitoring of the dielectric loss factor of power apparatus, most of them must meet strictly the synchronous sampling criterion, simultaneously with a precondition that the power frequency must be invariable in the sampling periods. Based on the instantaneous frequency theory, a unique definition and corresponding digital algorithm of instantaneous dielectric loss factor were presented, and a theoretical basis of the algorithm was deduced accordingly. By solving over-determined equations, the parameters of the equivalent parallel circuit can be obtained through recursive iterations, and thereafter the waveform of instantaneous dielectric loss factor can be figured out. Simulations and experimental results show that, under non-stationary signal conditions where power frequencies are randomly variable, the algorithm can accurately track the instantaneous frequency of power signals and recursively calculate the parameters of the equivalent parallel circuit. The proposed algorithm is not constrained by the prerequisite that the traditional algorithms are subjected to and renders good application performance, without being affected by the limitations incurred from synchronous sampling and harmonics. In addition, the acquired monitoring data from this algorithm are preferable for flexible treatment, which presents convenient utilization of mathematical statistics approach for further diagnostic analysis.