摘要
为了研究变压器绕组在多次短路冲击的累积效应影响下逐步机械形变问题,开展了多次110 kV真型变压器短路试验,采集了振动暂态信号和轴向压力稳态值,分析了历次短路过程中振动偏离和加权时频谱熵的变化趋势。结果表明,累积效应导致的绕组机械劣化会使振动加速度偏离未形变状态基准值,且加权时频谱熵增大;结合材料力学及绕组轴向振动动力学模型,推导出当振动加速度呈正偏离时,短路侧绕组形变形式为轴向外凸膨胀,反之为轴向内凹压缩的关联规律。最后提出并验证了一种基于振动偏差模值及加权时频谱熵联合分析的绕组形变辨识方法,该方法较传统阻抗法能够在绕组早期微小形变时更早发现机械稳定性下降。研究结果对变压器绕组形变预警具有一定指导意义。
The accumulative effect of transformer windings under multiple short-circuit impulse will eventually lead to sudden instability failure,so it is essential to study the mechanical deformation of windings under multiple short-circuit.Firstly,the multiple short-circuit tests under various working conditions on an 110 kV full-scale transformer were carried out,and the transient vibration acceleration signals during the short-circuit process and the steady-state values of the axial pressure of the windings before and after the multiple short-circuit were collected,the time-frequency characteristics of which were analyzed.According to the linear relationship between the vibration acceleration and the square of the current,the deviation trend between the measured value and the reference value is obtained,and the time domain characteristic of the vibration deviation is proposed.Then,combined with the winding axial vibration dynamics model,the relation between axial pressure,vibration deviation and deformation type is determined.Under HV-MV B-phase multiple short-circuit tests,the effective value of the vibration acceleration gradually produced a positive deviation.In the last test,the deviation value was^(2)1.5 m/s^(2),and the corresponding axial pressure was reduced from 3.15 t to 2.77 t.Similarly,under MV-LV A-phase multiple short-circuit tests,the vibration acceleration first produced a positive deviation of 2.37 m/s^(2) in the second test,and then gradually decreased.In the last test,it showed a negative deviation of-3.43 m/s^(2),and the corresponding axial pressure decreased from 4.29 t to 4.17 t and then increased to 4.43 t.According to the positive or negative deviation of the vibration acceleration under multiple-short circuit,the axial deformation type identification of the winding can be realized.When the vibration acceleration presents a positive deviation,the axial pressure decreases.The deformation form of the winding on the short circuit side is the outwards expansion of the end shaft.When the vibration acceleration presents a negative deviation,the axial pressure increases.At this time,the deformation form of the winding on the short circuit side is the inward concave compression of the end shaft.And the frequency domain characteristics of vibration weighted spectral entropy are proposed.For the HV-MV B-phase short-circuit condition,and M-L C-phase short circuit condition,the weighted entropy increases from 3.803 to 4.1,and 3.386 to 5.295 respectively.The weighted time-frequency spectrum entropy can be used as an effective frequency domain feature to identify whether the winding deformation occurs.The above result shows that when the mechanical degradation of winding caused by accumulative effect is occurred,the vibration acceleration will deviate the reference value of the undeformed state of winding,and the weighted time-frequency spectrum entropy will increase.Finally,a winding deformation identification method based on the joint analysis of vibration deviation and weighted time-frequency spectrum entropy is proposed and verified.This combined analysis method can avoid the problem that when the axial deformation type changes or the extend of deformation is small the characteristic quantity does not change significantly.Compared with the traditional impedance method,it is able to detect the mechanical degradation of winding earlier,which is more effectively to reflect the impact of the accumulative effect.The vibration signal is easy to collect,and the normal operation of the transformer will not be disturbed during collecting the signal,so as to realize the effective and reliable monitoring of the mechanical stability of the winding.
作者
律方成
汪鑫宇
王平
高树国
耿江海
LüFangcheng;Wang Xinyu;Wang Ping;Gao Shuguo;Geng Jianghai(Hebei Provincial Key Laboratory of Power Transmission Equipment Security Defense North China Electric Power University,Baoding 071003 China;State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University,Beijing 102206 China;State Grid Hebei Electric Power Research Institute,Shijiazhuang 050021 China)
出处
《电工技术学报》
EI
CSCD
北大核心
2023年第11期3022-3032,共11页
Transactions of China Electrotechnical Society
基金
河北省自然科学基金资助项目(E2021521004)。
关键词
变压器绕组
累积效应
短路冲击试验
时频特征分析
形变辨识
Transformer winding
accumulative effect
short circuit impact test
time-frequency analysis
mechanical deformation identification
