信号的取样方式对介质损耗角测量的影响  

Influence of signal sampling mode on dielectric loss angle measurement

作　　者：徐志钮[1] 谢红玲[1] 律方成[1] 王俊杰[1] 李和明[1] 

机构地区：[1]华北电力大学电气与电子工程学院,河北保定071003

出　　处：《电力自动化设备》2009年第7期48-51,55,共5页Electric Power Automation Equipment

摘　　要：分析了非整周期采样时介质损耗角(介损角)测量容易导致较大误差的问题,指出了电压和电流信号的取样方式对介损角测量的准确性有很大影响。如果信号中仅存在基波且传感器采集所得电压和电流信号同相位时,则非整周期采样的频谱泄漏和栅栏效应给介损角计算导致的误差将完全抵消,理论上介损角测量不会因为非整周期采样导致误差。仿真表明,在实际取样时若选择合适的传感器,直接使用DFT算法,即使非整周期采样严重时误差仍然很小,误差绝对值的最大值小于4×10-5 rad(设定的介损角0.003 rad)计算误差随设备介损角的增加而增大,介损角增大到0.02 rad时,误差绝对值的最大值约为2×10-4 rad;计算误差与直流分量关系不显著,直流分量在基波分量的10%范围内变化时,误差绝对值的最大值约为4×10-5 rad;计算误差随3次谐波的增加而线性增大,3次谐波分量达到基波分量的20%时,如果使用阻容串联电路模拟电容型设备,误差绝对值的最大值约为7×10-5 rad;如果使用阻容并联等值电路则同样条件下误差约为5×10-5 rad。因此,使用电容型设备末屏串入电容的电流取样方式能有效减少非整周期采样给介损角测量带来的误差。The larger dielectric loss angle measurement error caused by nonintegral period sampling is analyzed and it is pointed out that the accuracy of dielectric loss angle measurement is seriously influenced by the sampling mode of voltage and current signals. If the sampled voltage and current signals have only the fundamental components and have the same phase,the dielectric loss angle measurement error caused by the spectral leakage and fence effect in nonintegral period sampling is thoroughly counteracted,i.e, the dielectric loss angle measurement from nonintegral period sampling ＇is completely accurate in theory. Simulation shows that,when suitable sensors are selected and DFT algorithm is used to directly calculate the dielectric loss angle,the error is small even in severe nonintegral period sampling,the maximum error is less than 4× 10-^5rad（the dielectric loss angle is 0.003 rad）;the calculation error increases along with the dielectric loss angle,when the dielectric loss angle is 0.02 rad,the maximum error is about 2× 10-^4rad;the calculation error has little relationship with the direct current component,when it varies within 10 % of the fundamental component,the maximum error is about 4× 10-^5rad;the calculation error increases along with the third harmonic, when it reaches 20% of the fundamental component,the maximum error is about 7× 10-^5rad for serial resistor -capacitor circuit and about 5× 10-^5 rad for parallel resistor-capacitor circuit. The dielectric loss angle measurement error caused by noninteger sampling can be suppressed by sampling the current with a serial capacitor mounted at the capacitive equipment.

关 键 词：电容型设备 介损角 非整周期采样 取样方式 误差 

分 类 号：TM835.4[电气工程—高电压与绝缘技术]