基于TDFT非同步采样谐波测量的小电流接地故障信号处理方法

Signal processing method of small current grounding fault based on TDFT non synchronous sampling harmonic measurement

为解决10 kV配网线路高阻故障较多、间歇性接地故障较多、电弧不稳定、配电网网架结构复杂、分支线复杂、负荷随机分布等现象造成的配电网系统接地故障判别、选线、定位监测困难,采用基于TDFT非同步采样谐波测量算法的小电流接地判定算法进行故障判断、定位和隔离接地故障。站所终端DTU在硬件上采用ADSP-BF607作为主处理芯片,其具备DSP和ARM双处理架构,具有处理故障数据速度快、精度高、录波性能好等优势。基于TDFT非同步采样谐波测量算法,得出首半波小电流接地判定方法。为有效判断开关合闸瞬间的涌流,DTU采用离散傅立叶变换结果,通过加权算法变换实现抑制频谱泄漏误差。对传统算法、加窗算法和TDFT非同步采样谐波测量算法进行了比较分析。实验结果表明,基于TDFT非同步采样谐波测量的涌流和小电流接地故障算法设计在10 kV配网系统的小电流接地、隔离接地故障方面准确可靠。

In order to solve the difficulties in identifying,selecting and locating grounding faults caused by the phenomena of high resistance faults,intermittent grounding faults,arc instability,complex structure of distribution network,complex branch lines and random load distribution,the non-synchronous sampling harmonic measurement algorithm based on TDFT is adopted.The algorithm of current grounding judgement is used to distinguish,locate,and isolate grounding faults.The terminal DTU of station adopts ADSP-BF607 as the main processing chip in hardware.It has dual processing architecture of DSP and ARM,and owns the advantages of fast processing fault data,high accuracy and good recording performance.Based on the TDFT non synchronous sampling harmonic measurement algorithm,the first half wave small current grounding decision method is obtained.In order to effectively judge the inrush current at the moment of switch closing,the DTU adopts the results of Discrete Fourier Transform(DFT)and restrains the spectrum leakage error by weighted algorithm transformation.The traditional algorithm,windowing algorithm and TDFT asynchronous sampling harmonic measurement algorithm are compared and analyzed.The experimental results show that the design of inrush current and small current grounding fault algorithm based on TDFT asynchronous sampling harmonic measurement is accurate and reliable in the aspects of small current grounding and isolation grounding fault of 10 kV distribution network system.