单相短路时变压器角接绕组零序电流暂态特性及其影响

Transient Characteristics and Its Impact on Zero-sequence Current for Transformer Angle Connected Coil Under Single-phase Short-circuit Current

针对YNd11连接组的变压器,利用T形等效电路原理,结合对称分量法推导出了变压器角接绕组中零序电流(ih)分量与一次侧零序参量的关系式。通过实例,计算了一次侧发生单相接地短路时,变压器角接绕组中的暂态ih,并与MAT-LAB/Simulink计算结果进行对比,验证了该方法的有效性,并研究了影响ih的因素,研究表明ih与一次侧零序电流具有相似性,出现了零点漂移。当短路消失时,会引起包含多种频率成分的暂态振荡;当电源初相角α=0°(60°)和α=180°(120°)时的ih相对于时间轴对称,对于α=0°到180°,随着初始相角的增大,ih的首次过零时间也变短;ih峰值随着变压器时间常数的增大而增加;当τ≤0.2 ms时,ih增到无限大;ih峰值与短路点位置呈现抛物线特性。

Some impact would be brought about on angle connection winding of transformer caused by transient zero-sequence current when single phase grounding short current performing for large current grounding system. Aiming at YNdl 1 connection transformer, a method showing the relationship between zero-sequence current （ih） in angle connection coil of transformer and zero-sequence factors in primary winding is deducted by means of T equivalent circuit theory of transformer and symmetrical component method. Transient ih in angle connection coil of transformer is calculated on condition of single-phase grounding short circuit in high voltage overhead line, whose validity is verified compared with the results simulated by MATLAB/Simulink through some cases. Finally, some factors effec- ted on ih are studied. Results demonstrats that ih is similar to fault current, which possesses current-zero offset. The transient oscilla- tion containing many kinds of frequencies is arose when single phase fault vanished, ih are symmetrical relative to timer shaft when source epoch angle is α =0° （60°） and α = 180° （ 120°） , for α =0° to 180°, the first zero-crossing time shortened as epoch angle enlarging. The peak value of ih is enlarging with time constant of transformer enlarging and can be infinite if τ≤0. 2 ms. There is a parabola property between the peak values of ih and short circuit positions.